Generate website content

See:
- https://github.com/raphw/byte-buddy/releases/tag/byte-buddy-1.13.0
- https://github.com/raphw/byte-buddy/compare/byte-buddy-1.12.23...byte-buddy-1.13.0

.github/workflows/deploy-website.yaml

@@ -19,16 +19,21 @@ jobs:
           bundler-cache: true
       - name: Configure Github Pages
         uses: actions/configure-pages@v2.1.3
+      - name: Set up JDK
+        uses: actions/setup-java@v3.5.1
+        with:
+          java-version: 17.0.4
+          distribution: temurin
+          cache: maven
+      - name: Compile project and extract data
+        # XXX: Remove `-Dverification.{skip|warn}` and update `website/README.md`
+        # once module `docgen` has no errors.
+        run: |
+          mvn -T1C clean install -DskipTests -Dverification.warn
+          mvn -T1C clean install -DskipTests -Dverification.skip -Pdocgen
       - name: Generate documentation
-        run: ./generate-docs.sh
-      - name: Build website with Jekyll
         working-directory: ./website
-        run: bundle exec jekyll build
-      - name: Validate HTML output
-        working-directory: ./website
-        # XXX: Drop `--disable_external true` once we fully adopted the
-        # "Refaster rules" terminology on our website and in the code.
-        run: bundle exec htmlproofer --disable_external true --check-external-hash false ./_site
+        run: bundle exec ruby generate-docs.rb
       - name: Upload website as artifact
         uses: actions/upload-pages-artifact@v1.0.5
         with:

.mvn/maven.config

@@ -1 +1,3 @@
---batch-mode --errors --strict-checksums
+--batch-mode
+--errors
+--strict-checksums

README.md

@@ -36,7 +36,9 @@ code_][picnic-blog-ep-post].
 ### Installation
 
 This library is built on top of [Error Prone][error-prone-orig-repo]. To use
-it:
+it, read the installation guide for Maven or Gradle below.
+
+#### Maven
 
 1. First, follow Error Prone's [installation
    guide][error-prone-installation-guide].
@@ -94,6 +96,31 @@ it:
 Prone Support. Alternatively reference this project's `self-check` profile
 definition. -->
 
+#### Gradle
+
+1. First, follow the [installation guide]
+   [error-prone-gradle-installation-guide] of the `gradle-errorprone-plugin`.
+2. Next, edit your `build.gradle` file to add one or more Error Prone Support
+   modules:
+
+   ```groovy
+   dependencies {
+       // Error Prone itself.
+       errorprone("com.google.errorprone:error_prone_core:${errorProneVersion}")
+       // Error Prone Support's additional bug checkers.
+       errorprone("tech.picnic.error-prone-support:error-prone-contrib:${errorProneSupportVersion}")
+       // Error Prone Support's Refaster rules.
+       errorprone("tech.picnic.error-prone-support:refaster-runner:${errorProneSupportVersion}")
+   }
+
+   tasks.withType(JavaCompile).configureEach {
+       options.errorprone.disableWarningsInGeneratedCode = true
+       // Add other Error Prone flags here. See:
+       // - https://github.com/tbroyer/gradle-errorprone-plugin#configuration
+       // - https://errorprone.info/docs/flags
+   }
+   ```
+
 ### Seeing it in action
 
 Consider the following example code:
@@ -207,6 +234,7 @@ guidelines][contributing].
 [error-prone-bugchecker]: https://github.com/google/error-prone/blob/master/check_api/src/main/java/com/google/errorprone/bugpatterns/BugChecker.java
 [error-prone-fork-jitpack]: https://jitpack.io/#PicnicSupermarket/error-prone
 [error-prone-fork-repo]: https://github.com/PicnicSupermarket/error-prone
+[error-prone-gradle-installation-guide]: https://github.com/tbroyer/gradle-errorprone-plugin
 [error-prone-installation-guide]: https://errorprone.info/docs/installation#maven
 [error-prone-orig-repo]: https://github.com/google/error-prone
 [error-prone-pull-3301]: https://github.com/google/error-prone/pull/3301

documentation-support/pom.xml

@@ -0,0 +1,87 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <parent>
+        <groupId>tech.picnic.error-prone-support</groupId>
+        <artifactId>error-prone-support</artifactId>
+        <version>0.8.1-SNAPSHOT</version>
+    </parent>
+
+    <artifactId>documentation-support</artifactId>
+
+    <name>Picnic :: Error Prone Support :: Documentation Support</name>
+    <description>Data extraction support for the purpose of documentation generation.</description>
+
+    <dependencies>
+        <dependency>
+            <groupId>${groupId.error-prone}</groupId>
+            <artifactId>error_prone_annotation</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>${groupId.error-prone}</groupId>
+            <artifactId>error_prone_annotations</artifactId>
+            <scope>provided</scope>
+        </dependency>
+        <dependency>
+            <groupId>${groupId.error-prone}</groupId>
+            <artifactId>error_prone_check_api</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>${groupId.error-prone}</groupId>
+            <artifactId>error_prone_test_helpers</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>com.fasterxml.jackson.core</groupId>
+            <artifactId>jackson-annotations</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>com.fasterxml.jackson.core</groupId>
+            <artifactId>jackson-databind</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>com.google.auto</groupId>
+            <artifactId>auto-common</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>com.google.auto.service</groupId>
+            <artifactId>auto-service-annotations</artifactId>
+            <scope>provided</scope>
+        </dependency>
+        <dependency>
+            <groupId>com.google.auto.value</groupId>
+            <artifactId>auto-value-annotations</artifactId>
+            <scope>provided</scope>
+        </dependency>
+        <dependency>
+            <groupId>com.google.guava</groupId>
+            <artifactId>guava</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.jspecify</groupId>
+            <artifactId>jspecify</artifactId>
+            <scope>provided</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-api</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-engine</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-params</artifactId>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+</project>

documentation-support/src/main/java/tech/picnic/errorprone/documentation/BugPatternExtractor.java

@@ -0,0 +1,105 @@
+package tech.picnic.errorprone.documentation;
+
+import static com.google.common.base.Verify.verify;
+import static com.google.common.collect.ImmutableList.toImmutableList;
+import static java.util.Objects.requireNonNull;
+
+import com.google.auto.common.AnnotationMirrors;
+import com.google.auto.value.AutoValue;
+import com.google.common.collect.ImmutableList;
+import com.google.errorprone.BugPattern;
+import com.google.errorprone.BugPattern.SeverityLevel;
+import com.google.errorprone.VisitorState;
+import com.google.errorprone.annotations.Immutable;
+import com.google.errorprone.util.ASTHelpers;
+import com.sun.source.tree.AnnotationTree;
+import com.sun.source.tree.ClassTree;
+import com.sun.source.util.TaskEvent;
+import com.sun.tools.javac.code.Attribute;
+import com.sun.tools.javac.code.Symbol.ClassSymbol;
+import com.sun.tools.javac.util.Context;
+import javax.lang.model.element.AnnotationValue;
+import tech.picnic.errorprone.documentation.BugPatternExtractor.BugPatternDocumentation;
+
+/**
+ * An {@link Extractor} that describes how to extract data from a {@code @BugPattern} annotation.
+ */
+@Immutable
+final class BugPatternExtractor implements Extractor<BugPatternDocumentation> {
+  @Override
+  public BugPatternDocumentation extract(ClassTree tree, Context context, TaskEvent taskEvent) {
+    ClassSymbol symbol = ASTHelpers.getSymbol(tree);
+    BugPattern annotation = symbol.getAnnotation(BugPattern.class);
+    requireNonNull(annotation, "BugPattern annotation must be present");
+
+    return new AutoValue_BugPatternExtractor_BugPatternDocumentation(
+        symbol.getQualifiedName().toString(),
+        annotation.name().isEmpty() ? tree.getSimpleName().toString() : annotation.name(),
+        ImmutableList.copyOf(annotation.altNames()),
+        annotation.link(),
+        ImmutableList.copyOf(annotation.tags()),
+        annotation.summary(),
+        annotation.explanation(),
+        annotation.severity(),
+        annotation.disableable(),
+        annotation.documentSuppression() ? getSuppressionAnnotations(tree) : ImmutableList.of());
+  }
+
+  @Override
+  public boolean canExtract(ClassTree tree, VisitorState state) {
+    return ASTHelpers.hasDirectAnnotationWithSimpleName(tree, BugPattern.class.getSimpleName());
+  }
+
+  /**
+   * Returns the fully-qualified class names of suppression annotations specified by the {@link
+   * BugPattern} annotation located on the given tree.
+   *
+   * @implNote This method cannot simply invoke {@link BugPattern#suppressionAnnotations()}, as that
+   *     will yield an "Attempt to access Class objects for TypeMirrors" exception.
+   */
+  private static ImmutableList<String> getSuppressionAnnotations(ClassTree tree) {
+    AnnotationTree annotationTree =
+        ASTHelpers.getAnnotationWithSimpleName(
+            ASTHelpers.getAnnotations(tree), BugPattern.class.getSimpleName());
+    requireNonNull(annotationTree, "BugPattern annotation must be present");
+
+    Attribute.Array types =
+        doCast(
+            AnnotationMirrors.getAnnotationValue(
+                ASTHelpers.getAnnotationMirror(annotationTree), "suppressionAnnotations"),
+            Attribute.Array.class);
+
+    return types.getValue().stream()
+        .map(v -> doCast(v, Attribute.Class.class).classType.toString())
+        .collect(toImmutableList());
+  }
+
+  @SuppressWarnings("unchecked")
+  private static <T extends AnnotationValue> T doCast(AnnotationValue value, Class<T> target) {
+    verify(target.isInstance(value), "Value '%s' is not of type '%s'", value, target);
+    return (T) value;
+  }
+
+  @AutoValue
+  abstract static class BugPatternDocumentation {
+    abstract String fullyQualifiedName();
+
+    abstract String name();
+
+    abstract ImmutableList<String> altNames();
+
+    abstract String link();
+
+    abstract ImmutableList<String> tags();
+
+    abstract String summary();
+
+    abstract String explanation();
+
+    abstract SeverityLevel severityLevel();
+
+    abstract boolean canDisable();
+
+    abstract ImmutableList<String> suppressionAnnotations();
+  }
+}

documentation-support/src/main/java/tech/picnic/errorprone/documentation/BugPatternTestExtractor.java

@@ -0,0 +1,180 @@
+package tech.picnic.errorprone.documentation;
+
+import static com.google.errorprone.matchers.Matchers.hasAnnotation;
+import static com.google.errorprone.matchers.Matchers.instanceMethod;
+import static com.google.errorprone.matchers.method.MethodMatchers.staticMethod;
+
+import com.google.auto.value.AutoValue;
+import com.google.common.collect.ImmutableList;
+import com.google.errorprone.VisitorState;
+import com.google.errorprone.annotations.Immutable;
+import com.google.errorprone.annotations.Var;
+import com.google.errorprone.matchers.Matcher;
+import com.google.errorprone.util.ASTHelpers;
+import com.sun.source.tree.ClassTree;
+import com.sun.source.tree.ExpressionTree;
+import com.sun.source.tree.MemberSelectTree;
+import com.sun.source.tree.MethodInvocationTree;
+import com.sun.source.tree.MethodTree;
+import com.sun.source.util.TaskEvent;
+import com.sun.source.util.TreeScanner;
+import com.sun.tools.javac.util.Context;
+import java.util.ArrayList;
+import java.util.List;
+import org.jspecify.annotations.Nullable;
+import tech.picnic.errorprone.documentation.BugPatternTestExtractor.BugPatternTestDocumentation;
+
+/**
+ * An {@link Extractor} that describes how to extract data from a test that tests a {@code
+ * BugChecker}.
+ */
+@Immutable
+final class BugPatternTestExtractor implements Extractor<BugPatternTestDocumentation> {
+  private static final Matcher<MethodTree> JUNIT_TEST_METHOD =
+      hasAnnotation("org.junit.jupiter.api.Test");
+
+  // XXX: Improve support for correctly extracting multiple sources from a single
+  // `{BugCheckerRefactoring,Compilation}TestHelper` test.
+  @Override
+  public BugPatternTestDocumentation extract(ClassTree tree, Context context, TaskEvent event) {
+    VisitorState state = VisitorState.createForUtilityPurposes(context);
+    CollectBugPatternTests scanner = new CollectBugPatternTests(state);
+
+    tree.getMembers().stream()
+        .filter(MethodTree.class::isInstance)
+        .map(MethodTree.class::cast)
+        .filter(m -> JUNIT_TEST_METHOD.matches(m, state))
+        .forEach(m -> scanner.scan(m, null));
+
+    String className = tree.getSimpleName().toString();
+    return new AutoValue_BugPatternTestExtractor_BugPatternTestDocumentation(
+        className.substring(0, className.lastIndexOf("Test")),
+        scanner.getIdentificationTests(),
+        scanner.getReplacementTests());
+  }
+
+  @Override
+  public boolean canExtract(ClassTree tree, VisitorState state) {
+    String className = tree.getSimpleName().toString();
+    if (!className.endsWith("Test")) {
+      return false;
+    }
+
+    ScanBugPatternTest scanBugPatternTest = new ScanBugPatternTest();
+    scanBugPatternTest.scan(tree, state);
+
+    String bugPatternName = className.substring(0, className.lastIndexOf("Test"));
+    return scanBugPatternTest.hasTestUsingClassInstance(bugPatternName);
+  }
+
+  private static final class ScanBugPatternTest extends TreeScanner<@Nullable Void, VisitorState> {
+    private static final Matcher<ExpressionTree> BUG_PATTERN_TEST_METHOD =
+        staticMethod()
+            .onDescendantOfAny(
+                "com.google.errorprone.CompilationTestHelper",
+                "com.google.errorprone.BugCheckerRefactoringTestHelper")
+            .named("newInstance");
+
+    private final List<String> encounteredClasses = new ArrayList<>();
+
+    boolean hasTestUsingClassInstance(String clazz) {
+      return encounteredClasses.contains(clazz);
+    }
+
+    @Override
+    public @Nullable Void visitMethodInvocation(MethodInvocationTree node, VisitorState state) {
+      if (BUG_PATTERN_TEST_METHOD.matches(node, state)) {
+        MemberSelectTree firstArgumentTree = (MemberSelectTree) node.getArguments().get(0);
+        encounteredClasses.add(firstArgumentTree.getExpression().toString());
+      }
+      return super.visitMethodInvocation(node, state);
+    }
+  }
+
+  private static final class CollectBugPatternTests
+      extends TreeScanner<@Nullable Void, @Nullable Void> {
+    private static final Matcher<ExpressionTree> IDENTIFICATION_SOURCE_LINES =
+        instanceMethod()
+            .onDescendantOf("com.google.errorprone.CompilationTestHelper")
+            .named("addSourceLines");
+    private static final Matcher<ExpressionTree> REPLACEMENT_INPUT =
+        instanceMethod()
+            .onDescendantOf("com.google.errorprone.BugCheckerRefactoringTestHelper")
+            .named("addInputLines");
+    private static final Matcher<ExpressionTree> REPLACEMENT_OUTPUT =
+        instanceMethod()
+            .onDescendantOf("com.google.errorprone.BugCheckerRefactoringTestHelper.ExpectOutput")
+            .named("addOutputLines");
+
+    private final VisitorState state;
+    private final List<String> identificationTests = new ArrayList<>();
+    private final List<BugPatternReplacementTestDocumentation> replacementTests = new ArrayList<>();
+
+    @Var private String replacementOutputLines = "";
+
+    CollectBugPatternTests(VisitorState state) {
+      this.state = state;
+    }
+
+    public ImmutableList<String> getIdentificationTests() {
+      return ImmutableList.copyOf(identificationTests);
+    }
+
+    public ImmutableList<BugPatternReplacementTestDocumentation> getReplacementTests() {
+      return ImmutableList.copyOf(replacementTests);
+    }
+
+    @Override
+    public @Nullable Void visitMethodInvocation(MethodInvocationTree node, @Nullable Void unused) {
+      if (IDENTIFICATION_SOURCE_LINES.matches(node, state)) {
+        identificationTests.add(getSourceLines(node));
+      } else if (REPLACEMENT_INPUT.matches(node, state)) {
+        /* The visitor starts with `addOutputLines` and in the next visit it will go over the `addInputLines`. */
+        replacementTests.add(
+            BugPatternReplacementTestDocumentation.create(
+                getSourceLines(node), replacementOutputLines));
+      } else if (REPLACEMENT_OUTPUT.matches(node, state)) {
+        replacementOutputLines = getSourceLines(node);
+      }
+      return super.visitMethodInvocation(node, unused);
+    }
+
+    // XXX: Duplicate from `ErrorProneTestSourceFormat`, should we move this to `SourceCode` util?
+    private static String getSourceLines(MethodInvocationTree tree) {
+      List<? extends ExpressionTree> sourceLines =
+          tree.getArguments().subList(1, tree.getArguments().size());
+      StringBuilder source = new StringBuilder();
+
+      for (ExpressionTree sourceLine : sourceLines) {
+        Object value = ASTHelpers.constValue(sourceLine);
+        if (value == null) {
+          return "";
+        }
+        source.append(value).append('\n');
+      }
+
+      return source.toString();
+    }
+  }
+
+  @AutoValue
+  abstract static class BugPatternTestDocumentation {
+    abstract String name();
+
+    abstract ImmutableList<String> identificationTests();
+
+    abstract ImmutableList<BugPatternReplacementTestDocumentation> replacementTests();
+  }
+
+  @AutoValue
+  abstract static class BugPatternReplacementTestDocumentation {
+    static BugPatternReplacementTestDocumentation create(String sourceLines, String outputLines) {
+      return new AutoValue_BugPatternTestExtractor_BugPatternReplacementTestDocumentation(
+          sourceLines, outputLines);
+    }
+
+    abstract String inputLines();
+
+    abstract String outputLines();
+  }
+}

documentation-support/src/main/java/tech/picnic/errorprone/documentation/DocumentationGenerator.java

@@ -0,0 +1,56 @@
+package tech.picnic.errorprone.documentation;
+
+import static com.google.common.base.Preconditions.checkArgument;
+
+import com.google.auto.service.AutoService;
+import com.google.common.annotations.VisibleForTesting;
+import com.sun.source.util.JavacTask;
+import com.sun.source.util.Plugin;
+import com.sun.tools.javac.api.BasicJavacTask;
+import java.nio.file.InvalidPathException;
+import java.nio.file.Path;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+/**
+ * A compiler {@link Plugin} that analyzes and extracts relevant information for documentation
+ * purposes from processed files.
+ */
+// XXX: Find a better name for this class; it doesn't generate documentation per se.
+@AutoService(Plugin.class)
+public final class DocumentationGenerator implements Plugin {
+  @VisibleForTesting static final String OUTPUT_DIRECTORY_FLAG = "-XoutputDirectory";
+  private static final Pattern OUTPUT_DIRECTORY_FLAG_PATTERN =
+      Pattern.compile(Pattern.quote(OUTPUT_DIRECTORY_FLAG) + "=(.*)");
+
+  /** Instantiates a new {@link DocumentationGenerator} instance. */
+  public DocumentationGenerator() {}
+
+  @Override
+  public String getName() {
+    return getClass().getSimpleName();
+  }
+
+  @Override
+  public void init(JavacTask javacTask, String... args) {
+    checkArgument(args.length == 1, "Precisely one path must be provided");
+
+    javacTask.addTaskListener(
+        new DocumentationGeneratorTaskListener(
+            ((BasicJavacTask) javacTask).getContext(), getOutputPath(args[0])));
+  }
+
+  @VisibleForTesting
+  static Path getOutputPath(String pathArg) {
+    Matcher matcher = OUTPUT_DIRECTORY_FLAG_PATTERN.matcher(pathArg);
+    checkArgument(
+        matcher.matches(), "'%s' must be of the form '%s=<value>'", pathArg, OUTPUT_DIRECTORY_FLAG);
+
+    String path = matcher.group(1);
+    try {
+      return Path.of(path);
+    } catch (InvalidPathException e) {
+      throw new IllegalArgumentException(String.format("Invalid path '%s'", path), e);
+    }
+  }
+}

documentation-support/src/main/java/tech/picnic/errorprone/documentation/DocumentationGeneratorTaskListener.java

@@ -0,0 +1,92 @@
+package tech.picnic.errorprone.documentation;
+
+import static java.nio.charset.StandardCharsets.UTF_8;
+
+import com.fasterxml.jackson.annotation.JsonAutoDetect.Visibility;
+import com.fasterxml.jackson.annotation.PropertyAccessor;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.google.errorprone.VisitorState;
+import com.sun.source.tree.ClassTree;
+import com.sun.source.util.TaskEvent;
+import com.sun.source.util.TaskEvent.Kind;
+import com.sun.source.util.TaskListener;
+import com.sun.tools.javac.api.JavacTrees;
+import com.sun.tools.javac.util.Context;
+import java.io.File;
+import java.io.FileWriter;
+import java.io.IOException;
+import java.io.UncheckedIOException;
+import java.net.URI;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import javax.tools.JavaFileObject;
+
+/**
+ * A {@link TaskListener} that identifies and extracts relevant content for documentation generation
+ * and writes it to disk.
+ */
+// XXX: Find a better name for this class; it doesn't generate documentation per se.
+final class DocumentationGeneratorTaskListener implements TaskListener {
+  private static final ObjectMapper OBJECT_MAPPER =
+      new ObjectMapper().setVisibility(PropertyAccessor.FIELD, Visibility.ANY);
+
+  private final Context context;
+  private final Path docsPath;
+
+  DocumentationGeneratorTaskListener(Context context, Path path) {
+    this.context = context;
+    this.docsPath = path;
+  }
+
+  @Override
+  public void started(TaskEvent taskEvent) {
+    if (taskEvent.getKind() == Kind.ANALYZE) {
+      createDocsDirectory();
+    }
+  }
+
+  @Override
+  public void finished(TaskEvent taskEvent) {
+    if (taskEvent.getKind() != Kind.ANALYZE) {
+      return;
+    }
+
+    ClassTree classTree = JavacTrees.instance(context).getTree(taskEvent.getTypeElement());
+    JavaFileObject sourceFile = taskEvent.getSourceFile();
+    if (classTree == null || sourceFile == null) {
+      return;
+    }
+
+    ExtractorType.findMatchingType(classTree, VisitorState.createForUtilityPurposes(context))
+        .ifPresent(
+            extractorType ->
+                writeToFile(
+                    extractorType.getIdentifier(),
+                    getSimpleClassName(sourceFile.toUri()),
+                    extractorType.getExtractor().extract(classTree, context, taskEvent)));
+  }
+
+  private void createDocsDirectory() {
+    try {
+      Files.createDirectories(docsPath);
+    } catch (IOException e) {
+      throw new IllegalStateException(
+          String.format("Error while creating directory with path '%s'", docsPath), e);
+    }
+  }
+
+  private <T> void writeToFile(String identifier, String className, T data) {
+    File file = docsPath.resolve(String.format("%s-%s.json", identifier, className)).toFile();
+
+    try (FileWriter fileWriter = new FileWriter(file, UTF_8)) {
+      OBJECT_MAPPER.writeValue(fileWriter, data);
+    } catch (IOException e) {
+      throw new UncheckedIOException(String.format("Cannot write to file '%s'", file.getPath()), e);
+    }
+  }
+
+  private static String getSimpleClassName(URI path) {
+    return Paths.get(path).getFileName().toString().replace(".java", "");
+  }
+}

documentation-support/src/main/java/tech/picnic/errorprone/documentation/Extractor.java

@@ -0,0 +1,38 @@
+package tech.picnic.errorprone.documentation;
+
+import com.google.errorprone.VisitorState;
+import com.google.errorprone.annotations.Immutable;
+import com.sun.source.tree.ClassTree;
+import com.sun.source.util.TaskEvent;
+import com.sun.tools.javac.util.Context;
+
+/**
+ * Interface implemented by classes that define how to extract data of some type {@link T} from a
+ * given {@link ClassTree}.
+ *
+ * @param <T> The type of data that is extracted.
+ */
+@Immutable
+interface Extractor<T> {
+  /**
+   * Extracts and returns an instance of {@link T} using the provided arguments.
+   *
+   * @param tree      The {@link ClassTree} to analyze and from which to extract instances of {@link T}.
+   * @param context   The {@link Context} in which the current compilation takes place.
+   * @param taskEvent The {@link TaskEvent} in which the current compilation takes place.
+   * @return A non-null instance of {@link T}.
+   */
+  // XXX: Drop `Context` parameter unless used.
+  T extract(ClassTree tree, Context context, TaskEvent taskEvent);
+
+  /**
+   * Tells whether this {@link Extractor} can extract documentation content from the given {@link
+   * ClassTree}.
+   *
+   * @param tree The {@link ClassTree} of interest.
+   * @param state A {@link VisitorState} describes the context in which the given {@link ClassTree}
+   *     is found.
+   * @return {@code true} iff data extraction is supported.
+   */
+  boolean canExtract(ClassTree tree, VisitorState state);
+}

documentation-support/src/main/java/tech/picnic/errorprone/documentation/ExtractorType.java

@@ -0,0 +1,40 @@
+package tech.picnic.errorprone.documentation;
+
+import com.google.common.collect.ImmutableSet;
+import com.google.common.collect.Sets;
+import com.google.errorprone.VisitorState;
+import com.sun.source.tree.ClassTree;
+import java.util.EnumSet;
+import java.util.Optional;
+
+/** An enumeration of {@link Extractor} types. */
+enum ExtractorType {
+  BUG_PATTERN("bugpattern", new BugPatternExtractor()),
+  BUG_PATTERN_TEST("bugpattern-test", new BugPatternTestExtractor()),
+  //  REFASTER("refaster", new RefasterExtractor()),
+  REFASTER_TEMPLATE_TEST_INPUT("refaster-test-input", new RefasterTestExtractor()),
+  REFASTER_TEMPLATE_TEST_OUTPUT("refaster-test-output", new RefasterTestExtractor());
+
+  private static final ImmutableSet<ExtractorType> TYPES =
+      Sets.immutableEnumSet(EnumSet.allOf(ExtractorType.class));
+
+  private final String identifier;
+  private final Extractor<?> extractor;
+
+  ExtractorType(String identifier, Extractor<?> extractor) {
+    this.identifier = identifier;
+    this.extractor = extractor;
+  }
+
+  String getIdentifier() {
+    return identifier;
+  }
+
+  Extractor<?> getExtractor() {
+    return extractor;
+  }
+
+  static Optional<ExtractorType> findMatchingType(ClassTree tree, VisitorState state) {
+    return TYPES.stream().filter(type -> type.getExtractor().canExtract(tree, state)).findFirst();
+  }
+}

documentation-support/src/main/java/tech/picnic/errorprone/documentation/RefasterTestExtractor.java

@@ -0,0 +1,66 @@
+package tech.picnic.errorprone.documentation;
+
+import static com.google.common.collect.ImmutableList.toImmutableList;
+
+import com.google.auto.value.AutoValue;
+import com.google.common.collect.ImmutableList;
+import com.google.errorprone.VisitorState;
+import com.sun.source.tree.ClassTree;
+import com.sun.source.tree.MethodTree;
+import com.sun.source.util.TaskEvent;
+import com.sun.source.util.TreePath;
+import com.sun.tools.javac.util.Context;
+import java.util.List;
+
+public final class RefasterTestExtractor
+    implements Extractor<RefasterTestExtractor.RefasterTemplateCollectionTestData> {
+  @Override
+  public RefasterTemplateCollectionTestData extract(
+      ClassTree tree, Context context, TaskEvent taskEvent) {
+    String templateCollectionName = tree.getSimpleName().toString().replace("Test", "");
+    boolean isInput = taskEvent.getSourceFile().getName().contains("Input");
+    VisitorState stateWithPath =
+        VisitorState.createForUtilityPurposes(context)
+            .withPath(TreePath.getPath(taskEvent.getCompilationUnit(), tree));
+
+    ImmutableList<RefasterTemplateTestData> templateTests =
+        tree.getMembers().stream()
+            .filter(MethodTree.class::isInstance)
+            .map(MethodTree.class::cast)
+            .filter(m -> m.getName().toString().startsWith("test"))
+            .map(
+                m -> {
+                  String src = stateWithPath.getSourceForNode(tree);
+                  return new AutoValue_RefasterTestExtractor_RefasterTemplateTestData(
+                      m.getName().toString().replace("test", ""),
+                      src != null ? src : tree.toString());
+                })
+            .collect(toImmutableList());
+
+    return new AutoValue_RefasterTestExtractor_RefasterTemplateCollectionTestData(
+        templateCollectionName, isInput, templateTests);
+  }
+
+  @Override
+  public boolean canExtract(ClassTree tree, VisitorState state) {
+    String className = tree.getSimpleName().toString();
+    return className.endsWith("TestInput") || className.endsWith("TestOutput");
+  }
+
+  @AutoValue
+  abstract static class RefasterTemplateTestData {
+
+    abstract String templateName();
+
+    abstract String templateTestContent();
+  }
+
+  @AutoValue
+  abstract static class RefasterTemplateCollectionTestData {
+    abstract String templateCollection();
+
+    abstract boolean isInput();
+
+    abstract List<RefasterTemplateTestData> templateTests();
+  }
+}

documentation-support/src/main/java/tech/picnic/errorprone/documentation/package-info.java

@@ -0,0 +1,7 @@
+/**
+ * A Java compiler plugin that extracts data from compiled classes, in support of the Error Prone
+ * Support documentation.
+ */
+@com.google.errorprone.annotations.CheckReturnValue
+@org.jspecify.annotations.NullMarked
+package tech.picnic.errorprone.documentation;

documentation-support/src/test/java/tech/picnic/errorprone/documentation/BugPatternExtractorTest.java

@@ -0,0 +1,153 @@
+package tech.picnic.errorprone.documentation;
+
+import static com.google.errorprone.BugPattern.SeverityLevel.ERROR;
+import static java.nio.charset.StandardCharsets.UTF_8;
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+import com.google.common.io.Resources;
+import com.google.errorprone.BugPattern;
+import com.google.errorprone.CompilationTestHelper;
+import com.google.errorprone.VisitorState;
+import com.google.errorprone.bugpatterns.BugChecker;
+import com.google.errorprone.bugpatterns.BugChecker.ClassTreeMatcher;
+import com.google.errorprone.matchers.Description;
+import com.sun.source.tree.ClassTree;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+final class BugPatternExtractorTest {
+  @Test
+  void noBugPattern(@TempDir Path outputDirectory) {
+    Compilation.compileWithDocumentationGenerator(
+        outputDirectory,
+        "TestCheckerWithoutAnnotation.java",
+        "import com.google.errorprone.bugpatterns.BugChecker;",
+        "",
+        "public final class TestCheckerWithoutAnnotation extends BugChecker {}");
+
+    assertThat(outputDirectory.toAbsolutePath()).isEmptyDirectory();
+  }
+
+  @Test
+  void minimalBugPattern(@TempDir Path outputDirectory) throws IOException {
+    Compilation.compileWithDocumentationGenerator(
+        outputDirectory,
+        "MinimalBugChecker.java",
+        "package pkg;",
+        "",
+        "import com.google.errorprone.BugPattern;",
+        "import com.google.errorprone.BugPattern.SeverityLevel;",
+        "import com.google.errorprone.bugpatterns.BugChecker;",
+        "",
+        "@BugPattern(summary = \"MinimalBugChecker summary\", severity = SeverityLevel.ERROR)",
+        "public final class MinimalBugChecker extends BugChecker {}");
+
+    verifyFileMatchesResource(
+        outputDirectory,
+        "bugpattern-MinimalBugChecker.json",
+        "bugpattern-documentation-minimal.json");
+  }
+
+  @Test
+  void completeBugPattern(@TempDir Path outputDirectory) throws IOException {
+    Compilation.compileWithDocumentationGenerator(
+        outputDirectory,
+        "CompleteBugChecker.java",
+        "package pkg;",
+        "",
+        "import com.google.errorprone.BugPattern;",
+        "import com.google.errorprone.BugPattern.SeverityLevel;",
+        "import com.google.errorprone.bugpatterns.BugChecker;",
+        "import org.junit.jupiter.api.Test;",
+        "",
+        "@BugPattern(",
+        "    name = \"OtherName\",",
+        "    summary = \"CompleteBugChecker summary\",",
+        "    linkType = BugPattern.LinkType.CUSTOM,",
+        "    link = \"https://error-prone.picnic.tech\",",
+        "    explanation = \"Example explanation\",",
+        "    severity = SeverityLevel.SUGGESTION,",
+        "    altNames = \"Check\",",
+        "    tags = BugPattern.StandardTags.SIMPLIFICATION,",
+        "    disableable = false,",
+        "    suppressionAnnotations = {BugPattern.class, Test.class})",
+        "public final class CompleteBugChecker extends BugChecker {}");
+
+    verifyFileMatchesResource(
+        outputDirectory,
+        "bugpattern-CompleteBugChecker.json",
+        "bugpattern-documentation-complete.json");
+  }
+
+  @Test
+  void undocumentedSuppressionBugPattern(@TempDir Path outputDirectory) throws IOException {
+    Compilation.compileWithDocumentationGenerator(
+        outputDirectory,
+        "UndocumentedSuppressionBugPattern.java",
+        "package pkg;",
+        "",
+        "import com.google.errorprone.BugPattern;",
+        "import com.google.errorprone.BugPattern.SeverityLevel;",
+        "import com.google.errorprone.bugpatterns.BugChecker;",
+        "",
+        "@BugPattern(",
+        "    summary = \"UndocumentedSuppressionBugPattern summary\",",
+        "    severity = SeverityLevel.WARNING,",
+        "    documentSuppression = false)",
+        "public final class UndocumentedSuppressionBugPattern extends BugChecker {}");
+
+    verifyFileMatchesResource(
+        outputDirectory,
+        "bugpattern-UndocumentedSuppressionBugPattern.json",
+        "bugpattern-documentation-undocumented-suppression.json");
+  }
+
+  @Test
+  void bugPatternAnnotationIsAbsent() {
+    CompilationTestHelper.newInstance(TestChecker.class, getClass())
+        .addSourceLines(
+            "TestChecker.java",
+            "import com.google.errorprone.bugpatterns.BugChecker;",
+            "",
+            "// BUG: Diagnostic contains: Can extract: false",
+            "public final class TestChecker extends BugChecker {}")
+        .doTest();
+  }
+
+  private static void verifyFileMatchesResource(
+      Path outputDirectory, String fileName, String resourceName) throws IOException {
+    assertThat(Files.readString(outputDirectory.resolve(fileName)))
+        .isEqualToIgnoringWhitespace(getResource(resourceName));
+  }
+
+  // XXX: Once we support only JDK 15+, drop this method in favour of including the resources as
+  // text blocks in this class. (This also requires renaming the `verifyFileMatchesResource`
+  // method.)
+  private static String getResource(String resourceName) throws IOException {
+    return Resources.toString(
+        Resources.getResource(BugPatternExtractorTest.class, resourceName), UTF_8);
+  }
+
+  /** A {@link BugChecker} that validates the {@link BugPatternExtractor}. */
+  @BugPattern(summary = "Validates `BugPatternExtractor` extraction", severity = ERROR)
+  public static final class TestChecker extends BugChecker implements ClassTreeMatcher {
+    private static final long serialVersionUID = 1L;
+
+    @Override
+    public Description matchClass(ClassTree tree, VisitorState state) {
+      BugPatternExtractor extractor = new BugPatternExtractor();
+
+      assertThatThrownBy(() -> extractor.extract(tree, state.context, null))
+          .isInstanceOf(NullPointerException.class)
+          .hasMessage("BugPattern annotation must be present");
+
+      return buildDescription(tree)
+          .setMessage(String.format("Can extract: %s", extractor.canExtract(tree, state)))
+          .build();
+    }
+  }
+}

documentation-support/src/test/java/tech/picnic/errorprone/documentation/BugPatternTestExtractorTest.java

@@ -0,0 +1,337 @@
+package tech.picnic.errorprone.documentation;
+
+import static java.nio.charset.StandardCharsets.UTF_8;
+import static org.assertj.core.api.Assertions.assertThat;
+
+import com.google.common.io.Resources;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+final class BugPatternTestExtractorTest {
+  @Test
+  void noBugPatternTest(@TempDir Path outputDirectory) {
+    Compilation.compileWithDocumentationGenerator(
+        outputDirectory,
+        "TestCheckerWithoutAnnotation.java",
+        "import com.google.errorprone.bugpatterns.BugChecker;",
+        "",
+        "public final class TestCheckerWithoutAnnotation extends BugChecker {}");
+
+    assertThat(outputDirectory.toAbsolutePath()).isEmptyDirectory();
+  }
+
+  @Test
+  void minimalBugPatternTest(@TempDir Path outputDirectory) throws IOException {
+    Compilation.compileWithDocumentationGenerator(
+        outputDirectory,
+        "TestCheckerTest.java",
+        "import com.google.errorprone.BugCheckerRefactoringTestHelper;",
+        "import com.google.errorprone.bugpatterns.BugChecker;",
+        "import com.google.errorprone.CompilationTestHelper;",
+        "",
+        "final class TestCheckerTest {",
+        "  private static class TestChecker extends BugChecker {}",
+        "",
+        "  CompilationTestHelper compilationTestHelper = CompilationTestHelper.newInstance(TestChecker.class, getClass());",
+        "}");
+
+    verifyFileMatchesResource(
+        outputDirectory,
+        "bugpattern-test-TestCheckerTest.json",
+        "bugpattern-test-documentation-minimal.json");
+  }
+
+  @Test
+  void differentBugPatternAsClassVariableTest(@TempDir Path outputDirectory) {
+    Compilation.compileWithDocumentationGenerator(
+        outputDirectory,
+        "TestCheckerTest.java",
+        "import com.google.errorprone.BugCheckerRefactoringTestHelper;",
+        "import com.google.errorprone.bugpatterns.BugChecker;",
+        "import com.google.errorprone.CompilationTestHelper;",
+        "",
+        "final class TestCheckerTest {",
+        "  private static class DifferentChecker extends BugChecker {}",
+        "",
+        "  CompilationTestHelper compilationTestHelper = CompilationTestHelper.newInstance(DifferentChecker.class, getClass());",
+        "}");
+
+    assertThat(outputDirectory.toAbsolutePath()).isEmptyDirectory();
+  }
+
+  @Test
+  void differentBugPatternAsLocalVariable(@TempDir Path outputDirectory) {
+    Compilation.compileWithDocumentationGenerator(
+        outputDirectory,
+        "TestCheckerTest.java",
+        "import com.google.errorprone.bugpatterns.BugChecker;",
+        "import com.google.errorprone.CompilationTestHelper;",
+        "import org.junit.jupiter.api.Test;",
+        "",
+        "final class TestCheckerTest {",
+        "  private static class DifferentChecker extends BugChecker {}",
+        "",
+        "  @Test",
+        "  void identification() {",
+        "    CompilationTestHelper.newInstance(DifferentChecker.class, getClass())",
+        "        .addSourceLines(\"A.java\", \"class A {}\")",
+        "        .doTest();",
+        "  }",
+        "}");
+
+    assertThat(outputDirectory.toAbsolutePath()).isEmptyDirectory();
+  }
+
+  @Test
+  void bugPatternTestSingleIdentification(@TempDir Path outputDirectory) throws IOException {
+    Compilation.compileWithDocumentationGenerator(
+        outputDirectory,
+        "TestCheckerTest.java",
+        "import com.google.errorprone.bugpatterns.BugChecker;",
+        "import com.google.errorprone.CompilationTestHelper;",
+        "import org.junit.jupiter.api.Test;",
+        "",
+        "final class TestCheckerTest {",
+        "  private static class TestChecker extends BugChecker {}",
+        "",
+        "  @Test",
+        "  void identification() {",
+        "    CompilationTestHelper.newInstance(TestChecker.class, getClass())",
+        "        .addSourceLines(\"A.java\", \"class A {}\")",
+        "        .doTest();",
+        "  }",
+        "}");
+
+    verifyFileMatchesResource(
+        outputDirectory,
+        "bugpattern-test-TestCheckerTest.json",
+        "bugpattern-test-documentation-identification.json");
+  }
+
+  @Test
+  void bugPatternTestIdentificationMultipleSourceLines(@TempDir Path outputDirectory)
+      throws IOException {
+    Compilation.compileWithDocumentationGenerator(
+        outputDirectory,
+        "TestCheckerTest.java",
+        "package pkg;",
+        "",
+        "import com.google.errorprone.bugpatterns.BugChecker;",
+        "import com.google.errorprone.CompilationTestHelper;",
+        "import org.junit.jupiter.api.Test;",
+        "",
+        "final class TestCheckerTest {",
+        "  private static class TestChecker extends BugChecker {}",
+        "",
+        "  @Test",
+        "  void identification() {",
+        "    CompilationTestHelper.newInstance(TestChecker.class, getClass())",
+        "        .addSourceLines(\"A.java\", \"class A {}\")",
+        "        .addSourceLines(\"B.java\", \"class B {}\")",
+        "        .doTest();",
+        "  }",
+        "}");
+
+    verifyFileMatchesResource(
+        outputDirectory,
+        "bugpattern-test-TestCheckerTest.json",
+        "bugpattern-test-documentation-identification-two-sources.json");
+  }
+
+  @Test
+  void bugPatternTestSingleReplacement(@TempDir Path outputDirectory) throws IOException {
+    Compilation.compileWithDocumentationGenerator(
+        outputDirectory,
+        "TestCheckerTest.java",
+        "import com.google.errorprone.BugCheckerRefactoringTestHelper;",
+        "import com.google.errorprone.BugCheckerRefactoringTestHelper.TestMode;",
+        "import com.google.errorprone.bugpatterns.BugChecker;",
+        "import org.junit.jupiter.api.Test;",
+        "",
+        "final class TestCheckerTest {",
+        "  private static class TestChecker extends BugChecker {}",
+        "",
+        "  @Test",
+        "  void replacement() {",
+        "    BugCheckerRefactoringTestHelper.newInstance(TestChecker.class, getClass())",
+        "        .addInputLines(\"A.java\", \"class A {}\")",
+        "        .addOutputLines(\"A.java\", \"class A {}\")",
+        "        .doTest(TestMode.TEXT_MATCH);",
+        "  }",
+        "}");
+
+    verifyFileMatchesResource(
+        outputDirectory,
+        "bugpattern-test-TestCheckerTest.json",
+        "bugpattern-test-documentation-replacement.json");
+  }
+
+  @Test
+  void bugPatternTestMultipleReplacementSources(@TempDir Path outputDirectory) throws IOException {
+    Compilation.compileWithDocumentationGenerator(
+        outputDirectory,
+        "TestCheckerTest.java",
+        "import com.google.errorprone.BugCheckerRefactoringTestHelper;",
+        "import com.google.errorprone.BugCheckerRefactoringTestHelper.TestMode;",
+        "import com.google.errorprone.bugpatterns.BugChecker;",
+        "import org.junit.jupiter.api.Test;",
+        "",
+        "final class TestCheckerTest {",
+        "  private static class TestChecker extends BugChecker {}",
+        "",
+        "  @Test",
+        "  void replacement() {",
+        "    BugCheckerRefactoringTestHelper.newInstance(TestChecker.class, getClass())",
+        "        .addInputLines(\"A.java\", \"class A {}\")",
+        "        .addOutputLines(\"A.java\", \"class A {}\")",
+        "        .addInputLines(\"B.java\", \"class B {}\")",
+        "        .addOutputLines(\"B.java\", \"class B {}\")",
+        "        .doTest(TestMode.TEXT_MATCH);",
+        "  }",
+        "}");
+
+    verifyFileMatchesResource(
+        outputDirectory,
+        "bugpattern-test-TestCheckerTest.json",
+        "bugpattern-test-documentation-replacement-two-sources.json");
+  }
+
+  @Test
+  void bugPatternReplacementExpectUnchanged(@TempDir Path outputDirectory) throws IOException {
+    Compilation.compileWithDocumentationGenerator(
+        outputDirectory,
+        "TestCheckerTest.java",
+        "import com.google.errorprone.BugCheckerRefactoringTestHelper;",
+        "import com.google.errorprone.BugCheckerRefactoringTestHelper.TestMode;",
+        "import com.google.errorprone.bugpatterns.BugChecker;",
+        "import org.junit.jupiter.api.Test;",
+        "",
+        "final class TestCheckerTest {",
+        "  private static class TestChecker extends BugChecker {}",
+        "",
+        "  @Test",
+        "  void replacement() {",
+        "    BugCheckerRefactoringTestHelper.newInstance(TestChecker.class, getClass())",
+        "        .addInputLines(\"A.java\", \"class A {}\")",
+        "        .expectUnchanged()",
+        "        .doTest(TestMode.TEXT_MATCH);",
+        "  }",
+        "}");
+
+    verifyFileMatchesResource(
+        outputDirectory,
+        "bugpattern-test-TestCheckerTest.json",
+        "bugpattern-test-documentation-replacement-expect-unchanged.json");
+  }
+
+  @Test
+  void bugPatternTestIdentificationAndReplacement(@TempDir Path outputDirectory)
+      throws IOException {
+    Compilation.compileWithDocumentationGenerator(
+        outputDirectory,
+        "TestCheckerTest.java",
+        "import com.google.errorprone.BugCheckerRefactoringTestHelper;",
+        "import com.google.errorprone.BugCheckerRefactoringTestHelper.TestMode;",
+        "import com.google.errorprone.bugpatterns.BugChecker;",
+        "import com.google.errorprone.CompilationTestHelper;",
+        "import org.junit.jupiter.api.Test;",
+        "",
+        "final class TestCheckerTest {",
+        "  private static class TestChecker extends BugChecker {}",
+        "",
+        "  @Test",
+        "  void identification() {",
+        "    CompilationTestHelper.newInstance(TestChecker.class, getClass())",
+        "        .addSourceLines(\"A.java\", \"class A {}\")",
+        "        .doTest();",
+        "  }",
+        "",
+        "  @Test",
+        "  void replacement() {",
+        "    BugCheckerRefactoringTestHelper.newInstance(TestChecker.class, getClass())",
+        "        .addInputLines(\"A.java\", \"class A {}\")",
+        "        .addOutputLines(\"A.java\", \"class A {}\")",
+        "        .doTest(TestMode.TEXT_MATCH);",
+        "  }",
+        "}");
+
+    verifyFileMatchesResource(
+        outputDirectory,
+        "bugpattern-test-TestCheckerTest.json",
+        "bugpattern-test-documentation-identification-and-replacement.json");
+  }
+
+  @Test
+  void bugPatternTestMultipleIdentificationAndReplacement(@TempDir Path outputDirectory)
+      throws IOException {
+    Compilation.compileWithDocumentationGenerator(
+        outputDirectory,
+        "TestCheckerTest.java",
+        "package pkg;",
+        "",
+        "import static com.google.errorprone.BugCheckerRefactoringTestHelper.FixChoosers.SECOND;",
+        "",
+        "import com.google.errorprone.BugCheckerRefactoringTestHelper;",
+        "import com.google.errorprone.BugCheckerRefactoringTestHelper.TestMode;",
+        "import com.google.errorprone.bugpatterns.BugChecker;",
+        "import com.google.errorprone.CompilationTestHelper;",
+        "import org.junit.jupiter.api.Test;",
+        "",
+        "final class TestCheckerTest {",
+        "  private static class TestChecker extends BugChecker {}",
+        "",
+        "  @Test",
+        "  void identification() {",
+        "    CompilationTestHelper.newInstance(TestChecker.class, getClass())",
+        "        .addSourceLines(\"A.java\", \"class A {}\")",
+        "        .doTest();",
+        "  }",
+        "",
+        "  @Test",
+        "  void identification2() {",
+        "    CompilationTestHelper.newInstance(TestChecker.class, getClass())",
+        "        .addSourceLines(\"B.java\", \"class B {}\")",
+        "        .doTest();",
+        "  }",
+        "",
+        "  @Test",
+        "  void replacementFirstSuggestedFix() {",
+        "    BugCheckerRefactoringTestHelper.newInstance(TestChecker.class, getClass())",
+        "        .addInputLines(\"A.java\", \"class A {}\")",
+        "        .addOutputLines(\"A.java\", \"class A {}\")",
+        "        .doTest(TestMode.TEXT_MATCH);",
+        "  }",
+        "",
+        "  @Test",
+        "  void replacementSecondSuggestedFix() {",
+        "    BugCheckerRefactoringTestHelper.newInstance(TestChecker.class, getClass())",
+        "        .setFixChooser(SECOND)",
+        "        .addInputLines(\"B.java\", \"class B {}\")",
+        "        .addOutputLines(\"B.java\", \"class B {}\")",
+        "        .doTest(TestMode.TEXT_MATCH);",
+        "  }",
+        "}");
+
+    verifyFileMatchesResource(
+        outputDirectory,
+        "bugpattern-test-TestCheckerTest.json",
+        "bugpattern-test-documentation-multiple-identification-and-replacement.json");
+  }
+
+  private static void verifyFileMatchesResource(
+      Path outputDirectory, String fileName, String resourceName) throws IOException {
+    assertThat(Files.readString(outputDirectory.resolve(fileName)))
+        .isEqualToIgnoringWhitespace(getResource(resourceName));
+  }
+
+  // XXX: Once we support only JDK 15+, drop this method in favour of including the resources as
+  // text blocks in this class. (This also requires renaming the `verifyFileMatchesResource`
+  // method.)
+  private static String getResource(String resourceName) throws IOException {
+    return Resources.toString(
+        Resources.getResource(BugPatternTestExtractorTest.class, resourceName), UTF_8);
+  }
+}

documentation-support/src/test/java/tech/picnic/errorprone/documentation/Compilation.java

@@ -0,0 +1,45 @@
+package tech.picnic.errorprone.documentation;
+
+import com.google.common.collect.ImmutableList;
+import com.google.errorprone.FileManagers;
+import com.google.errorprone.FileObjects;
+import com.sun.tools.javac.api.JavacTaskImpl;
+import com.sun.tools.javac.api.JavacTool;
+import com.sun.tools.javac.file.JavacFileManager;
+import java.nio.file.Path;
+import javax.tools.JavaCompiler;
+import javax.tools.JavaFileObject;
+
+// XXX: Generalize and move this class so that it can also be used by `refaster-compiler`.
+// XXX: Add support for this class to the `ErrorProneTestHelperSourceFormat` check.
+public final class Compilation {
+  private Compilation() {}
+
+  public static void compileWithDocumentationGenerator(
+      Path outputDirectory, String fileName, String... lines) {
+    compileWithDocumentationGenerator(outputDirectory.toAbsolutePath().toString(), fileName, lines);
+  }
+
+  public static void compileWithDocumentationGenerator(
+      String outputDirectory, String fileName, String... lines) {
+    compile(
+        ImmutableList.of("-Xplugin:DocumentationGenerator -XoutputDirectory=" + outputDirectory),
+        FileObjects.forSourceLines(fileName, lines));
+  }
+
+  private static void compile(ImmutableList<String> options, JavaFileObject javaFileObject) {
+    JavacFileManager javacFileManager = FileManagers.testFileManager();
+    JavaCompiler compiler = JavacTool.create();
+    JavacTaskImpl task =
+        (JavacTaskImpl)
+            compiler.getTask(
+                null,
+                javacFileManager,
+                null,
+                options,
+                ImmutableList.of(),
+                ImmutableList.of(javaFileObject));
+
+    task.call();
+  }
+}

documentation-support/src/test/java/tech/picnic/errorprone/documentation/DocumentationGeneratorTaskListenerTest.java

@@ -0,0 +1,77 @@
+package tech.picnic.errorprone.documentation;
+
+import static com.google.common.collect.ImmutableList.toImmutableList;
+import static java.nio.file.attribute.AclEntryPermission.ADD_SUBDIRECTORY;
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+import static org.junit.jupiter.api.condition.OS.WINDOWS;
+
+import com.google.common.collect.ImmutableSet;
+import com.google.common.collect.Sets;
+import java.io.IOException;
+import java.nio.file.FileSystemException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.attribute.AclEntry;
+import java.nio.file.attribute.AclFileAttributeView;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.condition.DisabledOnOs;
+import org.junit.jupiter.api.condition.EnabledOnOs;
+import org.junit.jupiter.api.io.TempDir;
+
+final class DocumentationGeneratorTaskListenerTest {
+  @EnabledOnOs(WINDOWS)
+  @Test
+  void readOnlyFileSystemWindows(@TempDir Path outputDirectory) throws IOException {
+    AclFileAttributeView view =
+        Files.getFileAttributeView(outputDirectory, AclFileAttributeView.class);
+    view.setAcl(
+        view.getAcl().stream()
+            .map(
+                entry ->
+                    AclEntry.newBuilder(entry)
+                        .setPermissions(
+                            Sets.difference(entry.permissions(), ImmutableSet.of(ADD_SUBDIRECTORY)))
+                        .build())
+            .collect(toImmutableList()));
+
+    readOnlyFileSystemFailsToWrite(outputDirectory.resolve("nonexistent"));
+  }
+
+  @DisabledOnOs(WINDOWS)
+  @Test
+  void readOnlyFileSystemNonWindows(@TempDir Path outputDirectory) {
+    assertThat(outputDirectory.toFile().setWritable(false))
+        .describedAs("Failed to make test directory unwritable")
+        .isTrue();
+
+    readOnlyFileSystemFailsToWrite(outputDirectory.resolve("nonexistent"));
+  }
+
+  private static void readOnlyFileSystemFailsToWrite(Path outputDirectory) {
+    assertThatThrownBy(
+            () ->
+                Compilation.compileWithDocumentationGenerator(
+                    outputDirectory, "A.java", "class A {}"))
+        .hasRootCauseInstanceOf(FileSystemException.class)
+        .hasCauseInstanceOf(IllegalStateException.class)
+        .hasMessageEndingWith("Error while creating directory with path '%s'", outputDirectory);
+  }
+
+  @Test
+  void noClassNoOutput(@TempDir Path outputDirectory) {
+    Compilation.compileWithDocumentationGenerator(outputDirectory, "A.java", "package pkg;");
+
+    assertThat(outputDirectory).isEmptyDirectory();
+  }
+
+  @Test
+  void excessArguments(@TempDir Path outputDirectory) {
+    assertThatThrownBy(
+            () ->
+                Compilation.compileWithDocumentationGenerator(
+                    outputDirectory.toAbsolutePath() + " extra-arg", "A.java", "package pkg;"))
+        .isInstanceOf(IllegalArgumentException.class)
+        .hasMessage("Precisely one path must be provided");
+  }
+}

documentation-support/src/test/java/tech/picnic/errorprone/documentation/DocumentationGeneratorTest.java

@@ -0,0 +1,38 @@
+package tech.picnic.errorprone.documentation;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+import static tech.picnic.errorprone.documentation.DocumentationGenerator.OUTPUT_DIRECTORY_FLAG;
+
+import java.nio.file.InvalidPathException;
+import java.nio.file.Path;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
+
+final class DocumentationGeneratorTest {
+  @ParameterizedTest
+  @ValueSource(strings = {"bar", "foo"})
+  void getOutputPath(String path) {
+    assertThat(DocumentationGenerator.getOutputPath(OUTPUT_DIRECTORY_FLAG + '=' + path))
+        .isEqualTo(Path.of(path));
+  }
+
+  @ParameterizedTest
+  @ValueSource(strings = {"", "-XoutputDirectory", "invalidOption=Test", "nothing"})
+  void getOutputPathWithInvalidArgument(String pathArg) {
+    assertThatThrownBy(() -> DocumentationGenerator.getOutputPath(pathArg))
+        .isInstanceOf(IllegalArgumentException.class)
+        .hasMessage("'%s' must be of the form '%s=<value>'", pathArg, OUTPUT_DIRECTORY_FLAG);
+  }
+
+  @Test
+  void getOutputPathWithInvalidPath() {
+    String basePath = "path-with-null-char-\0";
+    assertThatThrownBy(
+            () -> DocumentationGenerator.getOutputPath(OUTPUT_DIRECTORY_FLAG + '=' + basePath))
+        .isInstanceOf(IllegalArgumentException.class)
+        .hasCauseInstanceOf(InvalidPathException.class)
+        .hasMessageEndingWith("Invalid path '%s'", basePath);
+  }
+}

documentation-support/src/test/resources/tech/picnic/errorprone/documentation/bugpattern-documentation-complete.json

@@ -0,0 +1,19 @@
+{
+  "fullyQualifiedName": "pkg.CompleteBugChecker",
+  "name": "OtherName",
+  "altNames": [
+    "Check"
+  ],
+  "link": "https://error-prone.picnic.tech",
+  "tags": [
+    "Simplification"
+  ],
+  "summary": "CompleteBugChecker summary",
+  "explanation": "Example explanation",
+  "severityLevel": "SUGGESTION",
+  "canDisable": false,
+  "suppressionAnnotations": [
+    "com.google.errorprone.BugPattern",
+    "org.junit.jupiter.api.Test"
+  ]
+}

documentation-support/src/test/resources/tech/picnic/errorprone/documentation/bugpattern-documentation-minimal.json

@@ -0,0 +1,14 @@
+{
+  "fullyQualifiedName": "pkg.MinimalBugChecker",
+  "name": "MinimalBugChecker",
+  "altNames": [],
+  "link": "",
+  "tags": [],
+  "summary": "MinimalBugChecker summary",
+  "explanation": "",
+  "severityLevel": "ERROR",
+  "canDisable": true,
+  "suppressionAnnotations": [
+    "java.lang.SuppressWarnings"
+  ]
+}

documentation-support/src/test/resources/tech/picnic/errorprone/documentation/bugpattern-documentation-undocumented-suppression.json

@@ -0,0 +1,12 @@
+{
+  "fullyQualifiedName": "pkg.UndocumentedSuppressionBugPattern",
+  "name": "UndocumentedSuppressionBugPattern",
+  "altNames": [],
+  "link": "",
+  "tags": [],
+  "summary": "UndocumentedSuppressionBugPattern summary",
+  "explanation": "",
+  "severityLevel": "WARNING",
+  "canDisable": true,
+  "suppressionAnnotations": []
+}

documentation-support/src/test/resources/tech/picnic/errorprone/documentation/bugpattern-test-documentation-identification-and-replacement.json

@@ -0,0 +1,12 @@
+{
+  "name": "TestChecker",
+  "identificationTests": [
+    "class A {}\n"
+  ],
+  "replacementTests": [
+    {
+      "inputLines": "class A {}\n",
+      "outputLines": "class A {}\n"
+    }
+  ]
+}

documentation-support/src/test/resources/tech/picnic/errorprone/documentation/bugpattern-test-documentation-identification-two-sources.json

@@ -0,0 +1,8 @@
+{
+  "name": "TestChecker",
+  "identificationTests": [
+    "class B {}\n",
+    "class A {}\n"
+  ],
+  "replacementTests": []
+}

documentation-support/src/test/resources/tech/picnic/errorprone/documentation/bugpattern-test-documentation-identification.json

@@ -0,0 +1,7 @@
+{
+  "name": "TestChecker",
+  "identificationTests": [
+    "class A {}\n"
+  ],
+  "replacementTests": []
+}

documentation-support/src/test/resources/tech/picnic/errorprone/documentation/bugpattern-test-documentation-minimal.json

@@ -0,0 +1,5 @@
+{
+  "name": "TestChecker",
+  "identificationTests": [],
+  "replacementTests": []
+}

documentation-support/src/test/resources/tech/picnic/errorprone/documentation/bugpattern-test-documentation-multiple-identification-and-replacement.json

@@ -0,0 +1,17 @@
+{
+  "name": "TestChecker",
+  "identificationTests": [
+    "class A {}\n",
+    "class B {}\n"
+  ],
+  "replacementTests": [
+    {
+      "inputLines": "class A {}\n",
+      "outputLines": "class A {}\n"
+    },
+    {
+      "inputLines": "class B {}\n",
+      "outputLines": "class B {}\n"
+    }
+  ]
+}

documentation-support/src/test/resources/tech/picnic/errorprone/documentation/bugpattern-test-documentation-replacement-expect-unchanged.json

@@ -0,0 +1,10 @@
+{
+  "name": "TestChecker",
+  "identificationTests": [],
+  "replacementTests": [
+    {
+      "inputLines": "class A {}\n",
+      "outputLines": ""
+    }
+  ]
+}

documentation-support/src/test/resources/tech/picnic/errorprone/documentation/bugpattern-test-documentation-replacement-two-sources.json

@@ -0,0 +1,14 @@
+{
+  "name": "TestChecker",
+  "identificationTests": [],
+  "replacementTests": [
+    {
+      "inputLines": "class B {}\n",
+      "outputLines": "class B {}\n"
+    },
+    {
+      "inputLines": "class A {}\n",
+      "outputLines": "class A {}\n"
+    }
+  ]
+}

documentation-support/src/test/resources/tech/picnic/errorprone/documentation/bugpattern-test-documentation-replacement.json

@@ -0,0 +1,10 @@
+{
+  "name": "TestChecker",
+  "identificationTests": [],
+  "replacementTests": [
+    {
+      "inputLines": "class A {}\n",
+      "outputLines": "class A {}\n"
+    }
+  ]
+}

error-prone-contrib/pom.xml

@@ -5,7 +5,7 @@
     <parent>
         <groupId>tech.picnic.error-prone-support</groupId>
         <artifactId>error-prone-support</artifactId>
-        <version>0.7.0</version>
+        <version>0.8.1-SNAPSHOT</version>
     </parent>
 
     <artifactId>error-prone-contrib</artifactId>
@@ -39,6 +39,14 @@
             <artifactId>error_prone_test_helpers</artifactId>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>${project.groupId}</groupId>
+            <artifactId>documentation-support</artifactId>
+            <!-- This dependency is declared only as a hint to Maven that
+            compilation depends on it; see the `maven-compiler-plugin`'s
+            `annotationProcessorPaths` configuration below. -->
+            <scope>provided</scope>
+        </dependency>
         <dependency>
             <groupId>${project.groupId}</groupId>
             <artifactId>refaster-support</artifactId>
@@ -213,6 +221,11 @@
                     <artifactId>maven-compiler-plugin</artifactId>
                     <configuration>
                         <annotationProcessorPaths combine.children="append">
+                            <path>
+                                <groupId>${project.groupId}</groupId>
+                                <artifactId>documentation-support</artifactId>
+                                <version>${project.version}</version>
+                            </path>
                             <path>
                                 <groupId>${project.groupId}</groupId>
                                 <artifactId>refaster-compiler</artifactId>
@@ -226,6 +239,7 @@
                         </annotationProcessorPaths>
                         <compilerArgs combine.children="append">
                             <arg>-Xplugin:RefasterRuleCompiler</arg>
+                            <arg>-Xplugin:DocumentationGenerator -XoutputDirectory=${project.build.directory}/docs</arg>
                         </compilerArgs>
                     </configuration>
                 </plugin>

error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/JUnitMethodDeclaration.java

@@ -9,7 +9,6 @@ import static com.google.errorprone.matchers.Matchers.hasModifier;
 import static com.google.errorprone.matchers.Matchers.not;
 import static java.util.function.Predicate.not;
 import static tech.picnic.errorprone.bugpatterns.util.Documentation.BUG_PATTERNS_BASE_URL;
-import static tech.picnic.errorprone.bugpatterns.util.JavaKeywords.isValidIdentifier;
 import static tech.picnic.errorprone.bugpatterns.util.MoreJUnitMatchers.SETUP_OR_TEARDOWN_METHOD;
 import static tech.picnic.errorprone.bugpatterns.util.MoreJUnitMatchers.TEST_METHOD;
 
@@ -25,15 +24,11 @@ import com.google.errorprone.fixes.SuggestedFixes;
 import com.google.errorprone.matchers.Description;
 import com.google.errorprone.matchers.Matcher;
 import com.google.errorprone.util.ASTHelpers;
-import com.sun.source.tree.ImportTree;
 import com.sun.source.tree.MethodTree;
-import com.sun.source.tree.Tree;
-import com.sun.tools.javac.code.Symbol;
 import com.sun.tools.javac.code.Symbol.MethodSymbol;
-import com.sun.tools.javac.code.Type;
 import java.util.Optional;
 import javax.lang.model.element.Modifier;
-import tech.picnic.errorprone.bugpatterns.util.SourceCode;
+import tech.picnic.errorprone.bugpatterns.util.ConflictDetection;
 
 /** A {@link BugChecker} that flags non-canonical JUnit method declarations. */
 // XXX: Consider introducing a class-level check that enforces that test classes:
@@ -90,7 +85,7 @@ public final class JUnitMethodDeclaration extends BugChecker implements MethodTr
     tryCanonicalizeMethodName(symbol)
         .ifPresent(
             newName ->
-                findMethodRenameBlocker(symbol, newName, state)
+                ConflictDetection.findMethodRenameBlocker(symbol, newName, state)
                     .ifPresentOrElse(
                         blocker -> reportMethodRenameBlocker(tree, blocker, state),
                         () -> fixBuilder.merge(SuggestedFixes.renameMethod(tree, newName, state))));
@@ -106,61 +101,7 @@ public final class JUnitMethodDeclaration extends BugChecker implements MethodTr
             .build());
   }
 
-  /**
-   * If applicable, returns a human-readable argument against assigning the given name to an
-   * existing method.
-   *
-   * <p>This method implements imperfect heuristics. Things it currently does not consider include
-   * the following:
-   *
-   * <ul>
-   *   <li>Whether the rename would merely introduce a method overload, rather than clashing with an
-   *       existing method declaration.
-   *   <li>Whether the rename would cause a method in a superclass to be overridden.
-   *   <li>Whether the rename would in fact clash with a static import. (It could be that a static
-   *       import of the same name is only referenced from lexical scopes in which the method under
-   *       consideration cannot be referenced directly.)
-   * </ul>
-   */
-  private static Optional<String> findMethodRenameBlocker(
-      MethodSymbol method, String newName, VisitorState state) {
-    if (isExistingMethodName(method.owner.type, newName, state)) {
-      return Optional.of(
-          String.format(
-              "a method named `%s` is already defined in this class or a supertype", newName));
-    }
-
-    if (isSimpleNameStaticallyImported(newName, state)) {
-      return Optional.of(String.format("`%s` is already statically imported", newName));
-    }
-
-    if (!isValidIdentifier(newName)) {
-      return Optional.of(String.format("`%s` is not a valid identifier", newName));
-    }
-
-    return Optional.empty();
-  }
-
-  private static boolean isExistingMethodName(Type clazz, String name, VisitorState state) {
-    return ASTHelpers.matchingMethods(state.getName(name), method -> true, clazz, state.getTypes())
-        .findAny()
-        .isPresent();
-  }
-
-  private static boolean isSimpleNameStaticallyImported(String simpleName, VisitorState state) {
-    return state.getPath().getCompilationUnit().getImports().stream()
-        .filter(ImportTree::isStatic)
-        .map(ImportTree::getQualifiedIdentifier)
-        .map(tree -> getStaticImportSimpleName(tree, state))
-        .anyMatch(simpleName::contentEquals);
-  }
-
-  private static CharSequence getStaticImportSimpleName(Tree tree, VisitorState state) {
-    String source = SourceCode.treeToString(tree, state);
-    return source.subSequence(source.lastIndexOf('.') + 1, source.length());
-  }
-
-  private static Optional<String> tryCanonicalizeMethodName(Symbol symbol) {
+  private static Optional<String> tryCanonicalizeMethodName(MethodSymbol symbol) {
     return Optional.of(symbol.getQualifiedName().toString())
         .filter(name -> name.startsWith(TEST_PREFIX))
         .map(name -> name.substring(TEST_PREFIX.length()))

error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/util/ConflictDetection.java

@@ -0,0 +1,75 @@
+package tech.picnic.errorprone.bugpatterns.util;
+
+import static tech.picnic.errorprone.bugpatterns.util.JavaKeywords.isValidIdentifier;
+
+import com.google.errorprone.VisitorState;
+import com.google.errorprone.util.ASTHelpers;
+import com.sun.source.tree.ImportTree;
+import com.sun.source.tree.Tree;
+import com.sun.tools.javac.code.Symbol.MethodSymbol;
+import com.sun.tools.javac.code.Type;
+import java.util.Optional;
+
+/** A set of helper methods for detecting conflicts that would be caused when applying fixes. */
+public final class ConflictDetection {
+  private ConflictDetection() {}
+
+  /**
+   * If applicable, returns a human-readable argument against assigning the given name to an
+   * existing method.
+   *
+   * <p>This method implements imperfect heuristics. Things it currently does not consider include
+   * the following:
+   *
+   * <ul>
+   *   <li>Whether the rename would merely introduce a method overload, rather than clashing with an
+   *       existing method declaration in its class or a supertype.
+   *   <li>Whether the rename would in fact clash with a static import. (It could be that a static
+   *       import of the same name is only referenced from lexical scopes in which the method under
+   *       consideration cannot be referenced directly.)
+   * </ul>
+   *
+   * @param method The method considered for renaming.
+   * @param newName The newly proposed name for the method.
+   * @param state The {@link VisitorState} to use when searching for blockers.
+   * @return A human-readable argument against assigning the proposed name to the given method, or
+   *     {@link Optional#empty()} if no blocker was found.
+   */
+  public static Optional<String> findMethodRenameBlocker(
+      MethodSymbol method, String newName, VisitorState state) {
+    if (isExistingMethodName(method.owner.type, newName, state)) {
+      return Optional.of(
+          String.format(
+              "a method named `%s` is already defined in this class or a supertype", newName));
+    }
+
+    if (isSimpleNameStaticallyImported(newName, state)) {
+      return Optional.of(String.format("`%s` is already statically imported", newName));
+    }
+
+    if (!isValidIdentifier(newName)) {
+      return Optional.of(String.format("`%s` is not a valid identifier", newName));
+    }
+
+    return Optional.empty();
+  }
+
+  private static boolean isExistingMethodName(Type clazz, String name, VisitorState state) {
+    return ASTHelpers.matchingMethods(state.getName(name), method -> true, clazz, state.getTypes())
+        .findAny()
+        .isPresent();
+  }
+
+  private static boolean isSimpleNameStaticallyImported(String simpleName, VisitorState state) {
+    return state.getPath().getCompilationUnit().getImports().stream()
+        .filter(ImportTree::isStatic)
+        .map(ImportTree::getQualifiedIdentifier)
+        .map(tree -> getStaticImportSimpleName(tree, state))
+        .anyMatch(simpleName::contentEquals);
+  }
+
+  private static CharSequence getStaticImportSimpleName(Tree tree, VisitorState state) {
+    String source = SourceCode.treeToString(tree, state);
+    return source.subSequence(source.lastIndexOf('.') + 1, source.length());
+  }
+}

error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/MapRules.java

@@ -1,5 +1,7 @@
 package tech.picnic.errorprone.refasterrules;
 
+import static java.util.Objects.requireNonNullElse;
+
 import com.google.errorprone.refaster.Refaster;
 import com.google.errorprone.refaster.annotation.AfterTemplate;
 import com.google.errorprone.refaster.annotation.BeforeTemplate;
@@ -43,6 +45,21 @@ final class MapRules {
     }
   }
 
+  /** Prefer {@link Map#getOrDefault(Object, Object)} over more contrived alternatives. */
+  // XXX: Note that `requireNonNullElse` throws an NPE if the second argument is `null`, while the
+  // alternative does not.
+  static final class MapGetOrDefault<K, V, T> {
+    @BeforeTemplate
+    V before(Map<K, V> map, T key, V defaultValue) {
+      return requireNonNullElse(map.get(key), defaultValue);
+    }
+
+    @AfterTemplate
+    V after(Map<K, V> map, T key, V defaultValue) {
+      return map.getOrDefault(key, defaultValue);
+    }
+  }
+
   /** Prefer {@link Map#isEmpty()} over more contrived alternatives. */
   static final class MapIsEmpty<K, V> {
     @BeforeTemplate

error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/ReactorRules.java

@@ -369,7 +369,8 @@ final class ReactorRules {
   static final class MonoIdentity<T> {
     @BeforeTemplate
     Mono<T> before(Mono<T> mono) {
-      return mono.switchIfEmpty(Mono.empty());
+      return Refaster.anyOf(
+          mono.switchIfEmpty(Mono.empty()), mono.flux().next(), mono.flux().singleOrEmpty());
     }
 
     @BeforeTemplate
@@ -473,6 +474,11 @@ final class ReactorRules {
    * Flux}.
    */
   abstract static class MonoFlatMapToFlux<T, S> {
+    // XXX: It would be more expressive if this `@Placeholder` were replaced with a `Function<?
+    // super T, ? extends Mono<? extends S>>` parameter, so that compatible non-lambda expression
+    // arguments to `flatMapMany` are also matched. However, the type inferred for lambda and method
+    // reference expressions passed to `flatMapMany` appears to always be `Function<T, Publisher<?
+    // extends S>>`, which doesn't match. Find a solution.
     @Placeholder(allowsIdentity = true)
     abstract Mono<S> transformation(@MayOptionallyUse T value);
 

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/AmbiguousJsonCreatorTest.java

@@ -3,21 +3,16 @@ package tech.picnic.errorprone.bugpatterns;
 import static com.google.common.base.Predicates.containsPattern;
 
 import com.google.errorprone.BugCheckerRefactoringTestHelper;
+import com.google.errorprone.BugCheckerRefactoringTestHelper.TestMode;
 import com.google.errorprone.CompilationTestHelper;
 import org.junit.jupiter.api.Test;
 
 final class AmbiguousJsonCreatorTest {
-  private final CompilationTestHelper compilationTestHelper =
-      CompilationTestHelper.newInstance(AmbiguousJsonCreator.class, getClass())
-          .expectErrorMessage(
-              "X",
-              containsPattern("`JsonCreator.Mode` should be set for single-argument creators"));
-  private final BugCheckerRefactoringTestHelper refactoringTestHelper =
-      BugCheckerRefactoringTestHelper.newInstance(AmbiguousJsonCreator.class, getClass());
-
   @Test
   void identification() {
-    compilationTestHelper
+    CompilationTestHelper.newInstance(AmbiguousJsonCreator.class, getClass())
+        .expectErrorMessage(
+            "X", containsPattern("`JsonCreator.Mode` should be set for single-argument creators"))
         .addSourceLines(
             "Container.java",
             "import com.fasterxml.jackson.annotation.JsonCreator;",
@@ -118,7 +113,7 @@ final class AmbiguousJsonCreatorTest {
 
   @Test
   void replacement() {
-    refactoringTestHelper
+    BugCheckerRefactoringTestHelper.newInstance(AmbiguousJsonCreator.class, getClass())
         .addInputLines(
             "A.java",
             "import com.fasterxml.jackson.annotation.JsonCreator;",
@@ -143,6 +138,6 @@ final class AmbiguousJsonCreatorTest {
             "    return FOO;",
             "  }",
             "}")
-        .doTest(BugCheckerRefactoringTestHelper.TestMode.TEXT_MATCH);
+        .doTest(TestMode.TEXT_MATCH);
   }
 }

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/AssertJIsNullTest.java

@@ -7,14 +7,9 @@ import com.google.errorprone.CompilationTestHelper;
 import org.junit.jupiter.api.Test;
 
 final class AssertJIsNullTest {
-  private final CompilationTestHelper compilationTestHelper =
-      CompilationTestHelper.newInstance(AssertJIsNull.class, getClass());
-  private final BugCheckerRefactoringTestHelper refactoringTestHelper =
-      BugCheckerRefactoringTestHelper.newInstance(AssertJIsNull.class, getClass());
-
   @Test
   void identification() {
-    compilationTestHelper
+    CompilationTestHelper.newInstance(AssertJIsNull.class, getClass())
         .addSourceLines(
             "A.java",
             "import static org.assertj.core.api.Assertions.assertThat;",
@@ -38,7 +33,7 @@ final class AssertJIsNullTest {
 
   @Test
   void replacement() {
-    refactoringTestHelper
+    BugCheckerRefactoringTestHelper.newInstance(AssertJIsNull.class, getClass())
         .addInputLines(
             "A.java",
             "import static org.assertj.core.api.Assertions.assertThat;",

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/AutowiredConstructorTest.java

@@ -6,14 +6,9 @@ import com.google.errorprone.CompilationTestHelper;
 import org.junit.jupiter.api.Test;
 
 final class AutowiredConstructorTest {
-  private final CompilationTestHelper compilationTestHelper =
-      CompilationTestHelper.newInstance(AutowiredConstructor.class, getClass());
-  private final BugCheckerRefactoringTestHelper refactoringTestHelper =
-      BugCheckerRefactoringTestHelper.newInstance(AutowiredConstructor.class, getClass());
-
   @Test
   void identification() {
-    compilationTestHelper
+    CompilationTestHelper.newInstance(AutowiredConstructor.class, getClass())
         .addSourceLines(
             "Container.java",
             "import com.google.errorprone.annotations.Immutable;",
@@ -71,7 +66,7 @@ final class AutowiredConstructorTest {
 
   @Test
   void replacement() {
-    refactoringTestHelper
+    BugCheckerRefactoringTestHelper.newInstance(AutowiredConstructor.class, getClass())
         .addInputLines(
             "Container.java",
             "import org.springframework.beans.factory.annotation.Autowired;",

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/CanonicalAnnotationSyntaxTest.java

@@ -6,14 +6,9 @@ import com.google.errorprone.CompilationTestHelper;
 import org.junit.jupiter.api.Test;
 
 final class CanonicalAnnotationSyntaxTest {
-  private final CompilationTestHelper compilationTestHelper =
-      CompilationTestHelper.newInstance(CanonicalAnnotationSyntax.class, getClass());
-  private final BugCheckerRefactoringTestHelper refactoringTestHelper =
-      BugCheckerRefactoringTestHelper.newInstance(CanonicalAnnotationSyntax.class, getClass());
-
   @Test
   void identification() {
-    compilationTestHelper
+    CompilationTestHelper.newInstance(CanonicalAnnotationSyntax.class, getClass())
         .addSourceLines(
             "pkg/A.java",
             "package pkg;",
@@ -133,7 +128,7 @@ final class CanonicalAnnotationSyntaxTest {
 
   @Test
   void replacement() {
-    refactoringTestHelper
+    BugCheckerRefactoringTestHelper.newInstance(CanonicalAnnotationSyntax.class, getClass())
         .addInputLines(
             "pkg/A.java",
             "package pkg;",

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/CollectorMutabilityTest.java

@@ -8,14 +8,9 @@ import com.google.errorprone.CompilationTestHelper;
 import org.junit.jupiter.api.Test;
 
 final class CollectorMutabilityTest {
-  private final CompilationTestHelper compilationTestHelper =
-      CompilationTestHelper.newInstance(CollectorMutability.class, getClass());
-  private final BugCheckerRefactoringTestHelper refactoringTestHelper =
-      BugCheckerRefactoringTestHelper.newInstance(CollectorMutability.class, getClass());
-
   @Test
   void identification() {
-    compilationTestHelper
+    CompilationTestHelper.newInstance(CollectorMutability.class, getClass())
         .addSourceLines(
             "A.java",
             "import static com.google.common.collect.ImmutableList.toImmutableList;",
@@ -67,7 +62,7 @@ final class CollectorMutabilityTest {
 
   @Test
   void identificationWithoutGuavaOnClasspath() {
-    compilationTestHelper
+    CompilationTestHelper.newInstance(CollectorMutability.class, getClass())
         .withClasspath()
         .addSourceLines(
             "A.java",
@@ -84,7 +79,7 @@ final class CollectorMutabilityTest {
 
   @Test
   void replacementFirstSuggestedFix() {
-    refactoringTestHelper
+    BugCheckerRefactoringTestHelper.newInstance(CollectorMutability.class, getClass())
         .addInputLines(
             "A.java",
             "import static java.util.stream.Collectors.toList;",
@@ -141,7 +136,7 @@ final class CollectorMutabilityTest {
 
   @Test
   void replacementSecondSuggestedFix() {
-    refactoringTestHelper
+    BugCheckerRefactoringTestHelper.newInstance(CollectorMutability.class, getClass())
         .setFixChooser(SECOND)
         .addInputLines(
             "A.java",

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/EmptyMethodTest.java

@@ -6,14 +6,9 @@ import com.google.errorprone.CompilationTestHelper;
 import org.junit.jupiter.api.Test;
 
 final class EmptyMethodTest {
-  private final CompilationTestHelper compilationTestHelper =
-      CompilationTestHelper.newInstance(EmptyMethod.class, getClass());
-  private final BugCheckerRefactoringTestHelper refactoringTestHelper =
-      BugCheckerRefactoringTestHelper.newInstance(EmptyMethod.class, getClass());
-
   @Test
   void identification() {
-    compilationTestHelper
+    CompilationTestHelper.newInstance(EmptyMethod.class, getClass())
         .addSourceLines(
             "A.java",
             "class A {",
@@ -69,7 +64,7 @@ final class EmptyMethodTest {
 
   @Test
   void replacement() {
-    refactoringTestHelper
+    BugCheckerRefactoringTestHelper.newInstance(EmptyMethod.class, getClass())
         .addInputLines(
             "A.java",
             "final class A {",

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/ErrorProneTestHelperSourceFormatTest.java

@@ -6,15 +6,9 @@ import com.google.errorprone.CompilationTestHelper;
 import org.junit.jupiter.api.Test;
 
 final class ErrorProneTestHelperSourceFormatTest {
-  private final CompilationTestHelper compilationTestHelper =
-      CompilationTestHelper.newInstance(ErrorProneTestHelperSourceFormat.class, getClass());
-  private final BugCheckerRefactoringTestHelper refactoringTestHelper =
-      BugCheckerRefactoringTestHelper.newInstance(
-          ErrorProneTestHelperSourceFormat.class, getClass());
-
   @Test
   void identification() {
-    compilationTestHelper
+    CompilationTestHelper.newInstance(ErrorProneTestHelperSourceFormat.class, getClass())
         .addSourceLines(
             "A.java",
             "import com.google.errorprone.BugCheckerRefactoringTestHelper;",
@@ -63,7 +57,7 @@ final class ErrorProneTestHelperSourceFormatTest {
      * Verifies that import sorting and code formatting is performed unconditionally, while unused
      * imports are removed unless part of a `BugCheckerRefactoringTestHelper` expected output file.
      */
-    refactoringTestHelper
+    BugCheckerRefactoringTestHelper.newInstance(ErrorProneTestHelperSourceFormat.class, getClass())
         .addInputLines(
             "A.java",
             "import com.google.errorprone.BugCheckerRefactoringTestHelper;",

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/ExplicitEnumOrderingTest.java

@@ -4,12 +4,9 @@ import com.google.errorprone.CompilationTestHelper;
 import org.junit.jupiter.api.Test;
 
 final class ExplicitEnumOrderingTest {
-  private final CompilationTestHelper compilationTestHelper =
-      CompilationTestHelper.newInstance(ExplicitEnumOrdering.class, getClass());
-
   @Test
   void identification() {
-    compilationTestHelper
+    CompilationTestHelper.newInstance(ExplicitEnumOrdering.class, getClass())
         .addSourceLines(
             "A.java",
             "import static java.lang.annotation.RetentionPolicy.CLASS;",

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/FluxFlatMapUsageTest.java

@@ -1,7 +1,5 @@
 package tech.picnic.errorprone.bugpatterns;
 
-import static com.google.errorprone.BugCheckerRefactoringTestHelper.newInstance;
-
 import com.google.errorprone.BugCheckerRefactoringTestHelper;
 import com.google.errorprone.BugCheckerRefactoringTestHelper.FixChoosers;
 import com.google.errorprone.BugCheckerRefactoringTestHelper.TestMode;
@@ -9,14 +7,9 @@ import com.google.errorprone.CompilationTestHelper;
 import org.junit.jupiter.api.Test;
 
 final class FluxFlatMapUsageTest {
-  private final CompilationTestHelper compilationTestHelper =
-      CompilationTestHelper.newInstance(FluxFlatMapUsage.class, getClass());
-  private final BugCheckerRefactoringTestHelper refactoringTestHelper =
-      newInstance(FluxFlatMapUsage.class, getClass());
-
   @Test
   void identification() {
-    compilationTestHelper
+    CompilationTestHelper.newInstance(FluxFlatMapUsage.class, getClass())
         .addSourceLines(
             "A.java",
             "import java.util.function.BiFunction;",
@@ -73,7 +66,7 @@ final class FluxFlatMapUsageTest {
 
   @Test
   void replacementFirstSuggestedFix() {
-    refactoringTestHelper
+    BugCheckerRefactoringTestHelper.newInstance(FluxFlatMapUsage.class, getClass())
         .setFixChooser(FixChoosers.FIRST)
         .addInputLines(
             "A.java",
@@ -108,7 +101,7 @@ final class FluxFlatMapUsageTest {
 
   @Test
   void replacementSecondSuggestedFix() {
-    refactoringTestHelper
+    BugCheckerRefactoringTestHelper.newInstance(FluxFlatMapUsage.class, getClass())
         .setFixChooser(FixChoosers.SECOND)
         .addInputLines(
             "A.java",

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/FormatStringConcatenationTest.java

@@ -6,14 +6,9 @@ import com.google.errorprone.CompilationTestHelper;
 import org.junit.jupiter.api.Test;
 
 final class FormatStringConcatenationTest {
-  private final CompilationTestHelper compilationTestHelper =
-      CompilationTestHelper.newInstance(FormatStringConcatenation.class, getClass());
-  private final BugCheckerRefactoringTestHelper refactoringTestHelper =
-      BugCheckerRefactoringTestHelper.newInstance(FormatStringConcatenation.class, getClass());
-
   @Test
   void identification() {
-    compilationTestHelper
+    CompilationTestHelper.newInstance(FormatStringConcatenation.class, getClass())
         .addSourceLines(
             "A.java",
             "import static com.google.common.base.Preconditions.checkArgument;",
@@ -309,7 +304,7 @@ final class FormatStringConcatenationTest {
 
   @Test
   void replacement() {
-    refactoringTestHelper
+    BugCheckerRefactoringTestHelper.newInstance(FormatStringConcatenation.class, getClass())
         .addInputLines(
             "A.java",
             "import static com.google.common.base.Preconditions.checkArgument;",

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/IdentityConversionTest.java

@@ -7,14 +7,9 @@ import com.google.errorprone.CompilationTestHelper;
 import org.junit.jupiter.api.Test;
 
 final class IdentityConversionTest {
-  private final CompilationTestHelper compilationTestHelper =
-      CompilationTestHelper.newInstance(IdentityConversion.class, getClass());
-  private final BugCheckerRefactoringTestHelper refactoringTestHelper =
-      BugCheckerRefactoringTestHelper.newInstance(IdentityConversion.class, getClass());
-
   @Test
   void identification() {
-    compilationTestHelper
+    CompilationTestHelper.newInstance(IdentityConversion.class, getClass())
         .addSourceLines(
             "A.java",
             "import static com.google.errorprone.matchers.Matchers.instanceMethod;",
@@ -184,7 +179,7 @@ final class IdentityConversionTest {
 
   @Test
   void replacementFirstSuggestedFix() {
-    refactoringTestHelper
+    BugCheckerRefactoringTestHelper.newInstance(IdentityConversion.class, getClass())
         .setFixChooser(FixChoosers.FIRST)
         .addInputLines(
             "A.java",
@@ -291,7 +286,7 @@ final class IdentityConversionTest {
 
   @Test
   void replacementSecondSuggestedFix() {
-    refactoringTestHelper
+    BugCheckerRefactoringTestHelper.newInstance(IdentityConversion.class, getClass())
         .setFixChooser(FixChoosers.SECOND)
         .addInputLines(
             "A.java",

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/ImmutablesSortedSetComparatorTest.java

@@ -6,14 +6,9 @@ import com.google.errorprone.CompilationTestHelper;
 import org.junit.jupiter.api.Test;
 
 final class ImmutablesSortedSetComparatorTest {
-  private final CompilationTestHelper compilationTestHelper =
-      CompilationTestHelper.newInstance(ImmutablesSortedSetComparator.class, getClass());
-  private final BugCheckerRefactoringTestHelper refactoringTestHelper =
-      BugCheckerRefactoringTestHelper.newInstance(ImmutablesSortedSetComparator.class, getClass());
-
   @Test
   void identification() {
-    compilationTestHelper
+    CompilationTestHelper.newInstance(ImmutablesSortedSetComparator.class, getClass())
         .addSourceLines(
             "A.java",
             "import com.google.common.collect.ContiguousSet;",
@@ -109,7 +104,7 @@ final class ImmutablesSortedSetComparatorTest {
 
   @Test
   void replacement() {
-    refactoringTestHelper
+    BugCheckerRefactoringTestHelper.newInstance(ImmutablesSortedSetComparator.class, getClass())
         .addInputLines(
             "A.java",
             "import com.google.common.collect.ImmutableSortedSet;",
@@ -147,7 +142,7 @@ final class ImmutablesSortedSetComparatorTest {
 
   @Test
   void replacementWithImportClash() {
-    refactoringTestHelper
+    BugCheckerRefactoringTestHelper.newInstance(ImmutablesSortedSetComparator.class, getClass())
         .addInputLines(
             "MySpringService.java",
             "import com.google.common.collect.ImmutableSortedSet;",

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/IsInstanceLambdaUsageTest.java

@@ -6,14 +6,9 @@ import com.google.errorprone.CompilationTestHelper;
 import org.junit.jupiter.api.Test;
 
 final class IsInstanceLambdaUsageTest {
-  private final CompilationTestHelper compilationTestHelper =
-      CompilationTestHelper.newInstance(IsInstanceLambdaUsage.class, getClass());
-  private final BugCheckerRefactoringTestHelper refactoringTestHelper =
-      BugCheckerRefactoringTestHelper.newInstance(IsInstanceLambdaUsage.class, getClass());
-
   @Test
   void identification() {
-    compilationTestHelper
+    CompilationTestHelper.newInstance(IsInstanceLambdaUsage.class, getClass())
         .addSourceLines(
             "A.java",
             "import java.util.stream.Stream;",
@@ -46,7 +41,7 @@ final class IsInstanceLambdaUsageTest {
 
   @Test
   void replacement() {
-    refactoringTestHelper
+    BugCheckerRefactoringTestHelper.newInstance(IsInstanceLambdaUsage.class, getClass())
         .addInputLines(
             "A.java",
             "import java.util.stream.Stream;",

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/JUnitClassModifiersTest.java

@@ -6,14 +6,9 @@ import com.google.errorprone.CompilationTestHelper;
 import org.junit.jupiter.api.Test;
 
 final class JUnitClassModifiersTest {
-  private final CompilationTestHelper compilationTestHelper =
-      CompilationTestHelper.newInstance(JUnitClassModifiers.class, getClass());
-  private final BugCheckerRefactoringTestHelper refactoringTestHelper =
-      BugCheckerRefactoringTestHelper.newInstance(JUnitClassModifiers.class, getClass());
-
   @Test
   void identification() {
-    compilationTestHelper
+    CompilationTestHelper.newInstance(JUnitClassModifiers.class, getClass())
         .addSourceLines(
             "Container.java",
             "import org.junit.jupiter.api.Test;",
@@ -98,7 +93,7 @@ final class JUnitClassModifiersTest {
 
   @Test
   void replacement() {
-    refactoringTestHelper
+    BugCheckerRefactoringTestHelper.newInstance(JUnitClassModifiers.class, getClass())
         .addInputLines(
             "A.java",
             "import org.junit.jupiter.api.Test;",

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/JUnitMethodDeclarationTest.java

@@ -6,14 +6,9 @@ import com.google.errorprone.CompilationTestHelper;
 import org.junit.jupiter.api.Test;
 
 final class JUnitMethodDeclarationTest {
-  private final CompilationTestHelper compilationTestHelper =
-      CompilationTestHelper.newInstance(JUnitMethodDeclaration.class, getClass());
-  private final BugCheckerRefactoringTestHelper refactoringTestHelper =
-      BugCheckerRefactoringTestHelper.newInstance(JUnitMethodDeclaration.class, getClass());
-
   @Test
   void identification() {
-    compilationTestHelper
+    CompilationTestHelper.newInstance(JUnitMethodDeclaration.class, getClass())
         .addSourceLines(
             "A.java",
             "import static org.junit.jupiter.params.provider.Arguments.arguments;",
@@ -345,7 +340,7 @@ final class JUnitMethodDeclarationTest {
 
   @Test
   void replacement() {
-    refactoringTestHelper
+    BugCheckerRefactoringTestHelper.newInstance(JUnitMethodDeclaration.class, getClass())
         .addInputLines(
             "A.java",
             "import static org.junit.jupiter.params.provider.Arguments.arguments;",

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/LexicographicalAnnotationAttributeListingTest.java

@@ -7,22 +7,9 @@ import com.google.errorprone.CompilationTestHelper;
 import org.junit.jupiter.api.Test;
 
 final class LexicographicalAnnotationAttributeListingTest {
-  private final CompilationTestHelper compilationTestHelper =
-      CompilationTestHelper.newInstance(
-          LexicographicalAnnotationAttributeListing.class, getClass());
-  private final CompilationTestHelper restrictedCompilationTestHelper =
-      CompilationTestHelper.newInstance(LexicographicalAnnotationAttributeListing.class, getClass())
-          .setArgs(
-              ImmutableList.of(
-                  "-XepOpt:LexicographicalAnnotationAttributeListing:Includes=pkg.A.Foo,pkg.A.Bar",
-                  "-XepOpt:LexicographicalAnnotationAttributeListing:Excludes=pkg.A.Bar#value"));
-  private final BugCheckerRefactoringTestHelper refactoringTestHelper =
-      BugCheckerRefactoringTestHelper.newInstance(
-          LexicographicalAnnotationAttributeListing.class, getClass());
-
   @Test
   void identification() {
-    compilationTestHelper
+    CompilationTestHelper.newInstance(LexicographicalAnnotationAttributeListing.class, getClass())
         .addSourceLines(
             "A.java",
             "import static java.math.RoundingMode.DOWN;",
@@ -165,7 +152,8 @@ final class LexicographicalAnnotationAttributeListingTest {
   // `CanonicalAnnotationSyntax` checker correct the situation in a subsequent run.
   @Test
   void replacement() {
-    refactoringTestHelper
+    BugCheckerRefactoringTestHelper.newInstance(
+            LexicographicalAnnotationAttributeListing.class, getClass())
         .addInputLines(
             "A.java",
             "import static java.math.RoundingMode.DOWN;",
@@ -246,7 +234,11 @@ final class LexicographicalAnnotationAttributeListingTest {
   @Test
   void filtering() {
     /* Some violations are not flagged because they are not in- or excluded. */
-    restrictedCompilationTestHelper
+    CompilationTestHelper.newInstance(LexicographicalAnnotationAttributeListing.class, getClass())
+        .setArgs(
+            ImmutableList.of(
+                "-XepOpt:LexicographicalAnnotationAttributeListing:Includes=pkg.A.Foo,pkg.A.Bar",
+                "-XepOpt:LexicographicalAnnotationAttributeListing:Excludes=pkg.A.Bar#value"))
         .addSourceLines(
             "pkg/A.java",
             "package pkg;",

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/LexicographicalAnnotationListingTest.java

@@ -6,15 +6,9 @@ import com.google.errorprone.CompilationTestHelper;
 import org.junit.jupiter.api.Test;
 
 final class LexicographicalAnnotationListingTest {
-  private final CompilationTestHelper compilationTestHelper =
-      CompilationTestHelper.newInstance(LexicographicalAnnotationListing.class, getClass());
-  private final BugCheckerRefactoringTestHelper refactoringTestHelper =
-      BugCheckerRefactoringTestHelper.newInstance(
-          LexicographicalAnnotationListing.class, getClass());
-
   @Test
   void identification() {
-    compilationTestHelper
+    CompilationTestHelper.newInstance(LexicographicalAnnotationListing.class, getClass())
         .addSourceLines(
             "A.java",
             "import java.lang.annotation.ElementType;",
@@ -133,7 +127,7 @@ final class LexicographicalAnnotationListingTest {
 
   @Test
   void replacement() {
-    refactoringTestHelper
+    BugCheckerRefactoringTestHelper.newInstance(LexicographicalAnnotationListing.class, getClass())
         .addInputLines(
             "A.java",
             "import java.lang.annotation.ElementType;",

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/MethodReferenceUsageTest.java

@@ -6,14 +6,9 @@ import com.google.errorprone.CompilationTestHelper;
 import org.junit.jupiter.api.Test;
 
 final class MethodReferenceUsageTest {
-  private final CompilationTestHelper compilationTestHelper =
-      CompilationTestHelper.newInstance(MethodReferenceUsage.class, getClass());
-  private final BugCheckerRefactoringTestHelper refactoringTestHelper =
-      BugCheckerRefactoringTestHelper.newInstance(MethodReferenceUsage.class, getClass());
-
   @Test
   void identification() {
-    compilationTestHelper
+    CompilationTestHelper.newInstance(MethodReferenceUsage.class, getClass())
         .addSourceLines(
             "A.java",
             "import com.google.common.collect.Streams;",
@@ -323,7 +318,7 @@ final class MethodReferenceUsageTest {
 
   @Test
   void replacement() {
-    refactoringTestHelper
+    BugCheckerRefactoringTestHelper.newInstance(MethodReferenceUsage.class, getClass())
         .addInputLines(
             "A.java",
             "import static java.util.Collections.emptyList;",

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/MissingRefasterAnnotationTest.java

@@ -6,16 +6,12 @@ import com.google.errorprone.CompilationTestHelper;
 import org.junit.jupiter.api.Test;
 
 final class MissingRefasterAnnotationTest {
-  private final CompilationTestHelper compilationTestHelper =
-      CompilationTestHelper.newInstance(MissingRefasterAnnotation.class, getClass())
-          .expectErrorMessage(
-              "X",
-              containsPattern(
-                  "The Refaster rule contains a method without any Refaster annotations"));
-
   @Test
   void identification() {
-    compilationTestHelper
+    CompilationTestHelper.newInstance(MissingRefasterAnnotation.class, getClass())
+        .expectErrorMessage(
+            "X",
+            containsPattern("The Refaster rule contains a method without any Refaster annotations"))
         .addSourceLines(
             "A.java",
             "import com.google.errorprone.refaster.annotation.AfterTemplate;",

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/MockitoStubbingTest.java

@@ -6,14 +6,9 @@ import com.google.errorprone.CompilationTestHelper;
 import org.junit.jupiter.api.Test;
 
 final class MockitoStubbingTest {
-  private final CompilationTestHelper compilationTestHelper =
-      CompilationTestHelper.newInstance(MockitoStubbing.class, getClass());
-  private final BugCheckerRefactoringTestHelper refactoringTestHelper =
-      BugCheckerRefactoringTestHelper.newInstance(MockitoStubbing.class, getClass());
-
   @Test
   void identification() {
-    compilationTestHelper
+    CompilationTestHelper.newInstance(MockitoStubbing.class, getClass())
         .addSourceLines(
             "A.java",
             "import static org.mockito.ArgumentMatchers.eq;",
@@ -55,7 +50,7 @@ final class MockitoStubbingTest {
 
   @Test
   void replacement() {
-    refactoringTestHelper
+    BugCheckerRefactoringTestHelper.newInstance(MockitoStubbing.class, getClass())
         .addInputLines(
             "A.java",
             "import static org.mockito.ArgumentMatchers.eq;",

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/NestedOptionalsTest.java

@@ -4,12 +4,9 @@ import com.google.errorprone.CompilationTestHelper;
 import org.junit.jupiter.api.Test;
 
 final class NestedOptionalsTest {
-  private final CompilationTestHelper compilationTestHelper =
-      CompilationTestHelper.newInstance(NestedOptionals.class, getClass());
-
   @Test
   void identification() {
-    compilationTestHelper
+    CompilationTestHelper.newInstance(NestedOptionals.class, getClass())
         .addSourceLines(
             "A.java",
             "import java.util.Optional;",
@@ -42,7 +39,7 @@ final class NestedOptionalsTest {
 
   @Test
   void identificationOptionalTypeNotLoaded() {
-    compilationTestHelper
+    CompilationTestHelper.newInstance(NestedOptionals.class, getClass())
         .addSourceLines(
             "A.java",
             "import java.time.Duration;",

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/NonEmptyMonoTest.java

@@ -7,14 +7,9 @@ import com.google.errorprone.CompilationTestHelper;
 import org.junit.jupiter.api.Test;
 
 final class NonEmptyMonoTest {
-  private final CompilationTestHelper compilationTestHelper =
-      CompilationTestHelper.newInstance(NonEmptyMono.class, getClass());
-  private final BugCheckerRefactoringTestHelper refactoringTestHelper =
-      BugCheckerRefactoringTestHelper.newInstance(NonEmptyMono.class, getClass());
-
   @Test
   void identification() {
-    compilationTestHelper
+    CompilationTestHelper.newInstance(NonEmptyMono.class, getClass())
         .addSourceLines(
             "A.java",
             "import static com.google.common.collect.ImmutableList.toImmutableList;",
@@ -111,7 +106,7 @@ final class NonEmptyMonoTest {
 
   @Test
   void replacement() {
-    refactoringTestHelper
+    BugCheckerRefactoringTestHelper.newInstance(NonEmptyMono.class, getClass())
         .addInputLines(
             "A.java",
             "import static com.google.common.collect.ImmutableList.toImmutableList;",

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/PrimitiveComparisonTest.java

@@ -5,22 +5,21 @@ import com.google.errorprone.BugCheckerRefactoringTestHelper.TestMode;
 import com.google.errorprone.CompilationTestHelper;
 import org.junit.jupiter.api.Test;
 
+// XXX: There are no tests for multiple replacements within the same expression:
+// - Error Prone doesn't currently support this, it seems.
+// - The `BugCheckerRefactoringTestHelper` throws an exception in this case.
+// - During actual compilation only the first replacement is applied.
+// XXX: Can we perhaps work-around this by describing the fixes in reverse order?
 final class PrimitiveComparisonTest {
-  private final CompilationTestHelper compilationTestHelper =
-      CompilationTestHelper.newInstance(PrimitiveComparison.class, getClass());
-  private final BugCheckerRefactoringTestHelper refactoringTestHelper =
-      BugCheckerRefactoringTestHelper.newInstance(PrimitiveComparison.class, getClass());
-
-  // XXX: There are no tests for multiple replacements within the same expression:
-  // - Error Prone doesn't currently support this, it seems.
-  // - The `BugCheckerRefactoringTestHelper` throws an exception in this case.
-  // - During actual compilation only the first replacement is applied.
-  // XXX: Can we perhaps work-around this by describing the fixes in reverse order?
-
-  // The logic for `char` and `short` is exactly analogous to the `byte` case.
+  /**
+   * Tests the identification of {@code byte} comparisons for which boxing can be avoided.
+   *
+   * @implNote The logic for {@code char} and {@code short} is exactly analogous to the {@code byte}
+   *     case.
+   */
   @Test
   void byteComparison() {
-    compilationTestHelper
+    CompilationTestHelper.newInstance(PrimitiveComparison.class, getClass())
         .addSourceLines(
             "A.java",
             "import java.util.Comparator;",
@@ -120,7 +119,7 @@ final class PrimitiveComparisonTest {
 
   @Test
   void intComparison() {
-    compilationTestHelper
+    CompilationTestHelper.newInstance(PrimitiveComparison.class, getClass())
         .addSourceLines(
             "A.java",
             "import java.util.Comparator;",
@@ -227,7 +226,7 @@ final class PrimitiveComparisonTest {
 
   @Test
   void longComparison() {
-    compilationTestHelper
+    CompilationTestHelper.newInstance(PrimitiveComparison.class, getClass())
         .addSourceLines(
             "A.java",
             "import java.util.Comparator;",
@@ -318,7 +317,7 @@ final class PrimitiveComparisonTest {
 
   @Test
   void floatComparison() {
-    compilationTestHelper
+    CompilationTestHelper.newInstance(PrimitiveComparison.class, getClass())
         .addSourceLines(
             "A.java",
             "import java.util.Comparator;",
@@ -386,7 +385,7 @@ final class PrimitiveComparisonTest {
 
   @Test
   void doubleComparison() {
-    compilationTestHelper
+    CompilationTestHelper.newInstance(PrimitiveComparison.class, getClass())
         .addSourceLines(
             "A.java",
             "import java.util.Comparator;",
@@ -461,7 +460,7 @@ final class PrimitiveComparisonTest {
 
   @Test
   void stringComparison() {
-    compilationTestHelper
+    CompilationTestHelper.newInstance(PrimitiveComparison.class, getClass())
         .addSourceLines(
             "A.java",
             "import java.util.Comparator;",
@@ -497,7 +496,7 @@ final class PrimitiveComparisonTest {
 
   @Test
   void replacementWithPrimitiveVariants() {
-    refactoringTestHelper
+    BugCheckerRefactoringTestHelper.newInstance(PrimitiveComparison.class, getClass())
         .addInputLines(
             "A.java",
             "import java.util.Comparator;",
@@ -577,7 +576,7 @@ final class PrimitiveComparisonTest {
 
   @Test
   void replacementWithBoxedVariants() {
-    refactoringTestHelper
+    BugCheckerRefactoringTestHelper.newInstance(PrimitiveComparison.class, getClass())
         .addInputLines(
             "A.java",
             "import java.util.Comparator;",
@@ -643,7 +642,7 @@ final class PrimitiveComparisonTest {
 
   @Test
   void replacementWithPrimitiveVariantsUsingStaticImports() {
-    refactoringTestHelper
+    BugCheckerRefactoringTestHelper.newInstance(PrimitiveComparison.class, getClass())
         .addInputLines(
             "A.java",
             "import static java.util.Comparator.comparing;",
@@ -682,7 +681,7 @@ final class PrimitiveComparisonTest {
 
   @Test
   void replacementWithBoxedVariantsUsingStaticImports() {
-    refactoringTestHelper
+    BugCheckerRefactoringTestHelper.newInstance(PrimitiveComparison.class, getClass())
         .addInputLines(
             "A.java",
             "import static java.util.Comparator.comparingDouble;",
@@ -723,7 +722,7 @@ final class PrimitiveComparisonTest {
 
   @Test
   void replacementWithPrimitiveVariantsInComplexSyntacticalContext() {
-    refactoringTestHelper
+    BugCheckerRefactoringTestHelper.newInstance(PrimitiveComparison.class, getClass())
         .addInputLines(
             "A.java",
             "import java.util.Comparator;",
@@ -755,7 +754,7 @@ final class PrimitiveComparisonTest {
 
   @Test
   void replacementWithBoxedVariantsInComplexSyntacticalContext() {
-    refactoringTestHelper
+    BugCheckerRefactoringTestHelper.newInstance(PrimitiveComparison.class, getClass())
         .addInputLines(
             "A.java",
             "import java.util.Comparator;",

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/RedundantStringConversionTest.java

@@ -12,13 +12,6 @@ import org.junit.jupiter.api.Test;
 final class RedundantStringConversionTest {
   private final CompilationTestHelper compilationTestHelper =
       CompilationTestHelper.newInstance(RedundantStringConversion.class, getClass());
-  private final CompilationTestHelper customizedCompilationTestHelper =
-      CompilationTestHelper.newInstance(RedundantStringConversion.class, getClass())
-          .setArgs(
-              ImmutableList.of(
-                  "-XepOpt:RedundantStringConversion:ExtraConversionMethods=java.lang.Enum#name(),A#name(),A.B#toString(int)"));
-  private final BugCheckerRefactoringTestHelper refactoringTestHelper =
-      BugCheckerRefactoringTestHelper.newInstance(RedundantStringConversion.class, getClass());
 
   @Test
   void identificationOfIdentityTransformation() {
@@ -416,7 +409,10 @@ final class RedundantStringConversionTest {
 
   @Test
   void identificationOfCustomConversionMethod() {
-    customizedCompilationTestHelper
+    CompilationTestHelper.newInstance(RedundantStringConversion.class, getClass())
+        .setArgs(
+            ImmutableList.of(
+                "-XepOpt:RedundantStringConversion:ExtraConversionMethods=java.lang.Enum#name(),A#name(),A.B#toString(int)"))
         .addSourceLines(
             "A.java",
             "import java.math.RoundingMode;",
@@ -509,7 +505,7 @@ final class RedundantStringConversionTest {
 
   @Test
   void replacement() {
-    refactoringTestHelper
+    BugCheckerRefactoringTestHelper.newInstance(RedundantStringConversion.class, getClass())
         .addInputLines(
             "A.java",
             "class A {",

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/RefasterAnyOfUsageTest.java

@@ -6,14 +6,9 @@ import com.google.errorprone.CompilationTestHelper;
 import org.junit.jupiter.api.Test;
 
 final class RefasterAnyOfUsageTest {
-  private final CompilationTestHelper compilationTestHelper =
-      CompilationTestHelper.newInstance(RefasterAnyOfUsage.class, getClass());
-  private final BugCheckerRefactoringTestHelper refactoringTestHelper =
-      BugCheckerRefactoringTestHelper.newInstance(RefasterAnyOfUsage.class, getClass());
-
   @Test
   void identification() {
-    compilationTestHelper
+    CompilationTestHelper.newInstance(RefasterAnyOfUsage.class, getClass())
         .addSourceLines(
             "A.java",
             "import com.google.errorprone.refaster.Refaster;",
@@ -38,7 +33,7 @@ final class RefasterAnyOfUsageTest {
 
   @Test
   void replacement() {
-    refactoringTestHelper
+    BugCheckerRefactoringTestHelper.newInstance(RefasterAnyOfUsage.class, getClass())
         .addInputLines(
             "A.java",
             "import com.google.errorprone.refaster.Refaster;",

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/RefasterRuleModifiersTest.java

@@ -6,14 +6,9 @@ import com.google.errorprone.CompilationTestHelper;
 import org.junit.jupiter.api.Test;
 
 final class RefasterRuleModifiersTest {
-  private final CompilationTestHelper compilationTestHelper =
-      CompilationTestHelper.newInstance(RefasterRuleModifiers.class, getClass());
-  private final BugCheckerRefactoringTestHelper refactoringTestHelper =
-      BugCheckerRefactoringTestHelper.newInstance(RefasterRuleModifiers.class, getClass());
-
   @Test
   void identification() {
-    compilationTestHelper
+    CompilationTestHelper.newInstance(RefasterRuleModifiers.class, getClass())
         .addSourceLines(
             "A.java",
             "import com.google.errorprone.refaster.annotation.BeforeTemplate;",
@@ -136,7 +131,7 @@ final class RefasterRuleModifiersTest {
 
   @Test
   void replacement() {
-    refactoringTestHelper
+    BugCheckerRefactoringTestHelper.newInstance(RefasterRuleModifiers.class, getClass())
         .addInputLines(
             "A.java",
             "import com.google.errorprone.refaster.annotation.BeforeTemplate;",

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/RequestMappingAnnotationTest.java

@@ -4,12 +4,9 @@ import com.google.errorprone.CompilationTestHelper;
 import org.junit.jupiter.api.Test;
 
 final class RequestMappingAnnotationTest {
-  private final CompilationTestHelper compilationTestHelper =
-      CompilationTestHelper.newInstance(RequestMappingAnnotation.class, getClass());
-
   @Test
   void identification() {
-    compilationTestHelper
+    CompilationTestHelper.newInstance(RequestMappingAnnotation.class, getClass())
         .addSourceLines(
             "A.java",
             "import java.io.InputStream;",

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/RequestParamTypeTest.java

@@ -4,16 +4,9 @@ import com.google.errorprone.CompilationTestHelper;
 import org.junit.jupiter.api.Test;
 
 final class RequestParamTypeTest {
-  private final CompilationTestHelper compilationTestHelper =
-      CompilationTestHelper.newInstance(RequestParamType.class, getClass());
-  private final CompilationTestHelper restrictedCompilationTestHelper =
-      CompilationTestHelper.newInstance(RequestParamType.class, getClass())
-          .setArgs(
-              "-XepOpt:RequestParamType:SupportedCustomTypes=com.google.common.collect.ImmutableSet,com.google.common.collect.ImmutableSortedMultiset");
-
   @Test
   void identification() {
-    compilationTestHelper
+    CompilationTestHelper.newInstance(RequestParamType.class, getClass())
         .addSourceLines(
             "A.java",
             "import com.google.common.collect.ImmutableBiMap;",
@@ -70,7 +63,9 @@ final class RequestParamTypeTest {
 
   @Test
   void identificationRestricted() {
-    restrictedCompilationTestHelper
+    CompilationTestHelper.newInstance(RequestParamType.class, getClass())
+        .setArgs(
+            "-XepOpt:RequestParamType:SupportedCustomTypes=com.google.common.collect.ImmutableSet,com.google.common.collect.ImmutableSortedMultiset")
         .addSourceLines(
             "A.java",
             "import com.google.common.collect.ImmutableBiMap;",

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/ScheduledTransactionTraceTest.java

@@ -7,14 +7,9 @@ import org.junit.jupiter.api.Test;
 import org.springframework.scheduling.annotation.Scheduled;
 
 final class ScheduledTransactionTraceTest {
-  private final CompilationTestHelper compilationTestHelper =
-      CompilationTestHelper.newInstance(ScheduledTransactionTrace.class, getClass());
-  private final BugCheckerRefactoringTestHelper refactoringTestHelper =
-      BugCheckerRefactoringTestHelper.newInstance(ScheduledTransactionTrace.class, getClass());
-
   @Test
   void identification() {
-    compilationTestHelper
+    CompilationTestHelper.newInstance(ScheduledTransactionTrace.class, getClass())
         .addSourceLines(
             "A.java",
             "import com.newrelic.api.agent.Trace;",
@@ -46,7 +41,7 @@ final class ScheduledTransactionTraceTest {
 
   @Test
   void identificationWithoutNewRelicAgentApiOnClasspath() {
-    compilationTestHelper
+    CompilationTestHelper.newInstance(ScheduledTransactionTrace.class, getClass())
         .withClasspath(Scheduled.class)
         .addSourceLines(
             "A.java",
@@ -61,7 +56,7 @@ final class ScheduledTransactionTraceTest {
 
   @Test
   void replacement() {
-    refactoringTestHelper
+    BugCheckerRefactoringTestHelper.newInstance(ScheduledTransactionTrace.class, getClass())
         .addInputLines(
             "A.java",
             "import com.newrelic.api.agent.Trace;",

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/Slf4jLogStatementTest.java

@@ -6,14 +6,9 @@ import com.google.errorprone.CompilationTestHelper;
 import org.junit.jupiter.api.Test;
 
 final class Slf4jLogStatementTest {
-  private final CompilationTestHelper compilationTestHelper =
-      CompilationTestHelper.newInstance(Slf4jLogStatement.class, getClass());
-  private final BugCheckerRefactoringTestHelper refactoringTestHelper =
-      BugCheckerRefactoringTestHelper.newInstance(Slf4jLogStatement.class, getClass());
-
   @Test
   void identification() {
-    compilationTestHelper
+    CompilationTestHelper.newInstance(Slf4jLogStatement.class, getClass())
         .addSourceLines(
             "A.java",
             "import org.slf4j.Logger;",
@@ -96,7 +91,7 @@ final class Slf4jLogStatementTest {
   // XXX: Drop what's unused.
   @Test
   void replacement() {
-    refactoringTestHelper
+    BugCheckerRefactoringTestHelper.newInstance(Slf4jLogStatement.class, getClass())
         .addInputLines(
             "A.java",
             "import org.slf4j.Logger;",

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/SpringMvcAnnotationTest.java

@@ -6,14 +6,9 @@ import com.google.errorprone.CompilationTestHelper;
 import org.junit.jupiter.api.Test;
 
 final class SpringMvcAnnotationTest {
-  private final CompilationTestHelper compilationTestHelper =
-      CompilationTestHelper.newInstance(SpringMvcAnnotation.class, getClass());
-  private final BugCheckerRefactoringTestHelper refactoringTestHelper =
-      BugCheckerRefactoringTestHelper.newInstance(SpringMvcAnnotation.class, getClass());
-
   @Test
   void identification() {
-    compilationTestHelper
+    CompilationTestHelper.newInstance(SpringMvcAnnotation.class, getClass())
         .addSourceLines(
             "A.java",
             "import static org.springframework.web.bind.annotation.RequestMethod.DELETE;",
@@ -85,7 +80,7 @@ final class SpringMvcAnnotationTest {
 
   @Test
   void replacement() {
-    refactoringTestHelper
+    BugCheckerRefactoringTestHelper.newInstance(SpringMvcAnnotation.class, getClass())
         .addInputLines(
             "A.java",
             "import static org.springframework.web.bind.annotation.RequestMethod.PATCH;",

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/StaticImportTest.java

@@ -8,11 +8,6 @@ import com.google.errorprone.CompilationTestHelper;
 import org.junit.jupiter.api.Test;
 
 final class StaticImportTest {
-  private final CompilationTestHelper compilationTestHelper =
-      CompilationTestHelper.newInstance(StaticImport.class, getClass());
-  private final BugCheckerRefactoringTestHelper refactoringTestHelper =
-      BugCheckerRefactoringTestHelper.newInstance(StaticImport.class, getClass());
-
   @Test
   void candidateMethodsAreNotRedundant() {
     assertThat(StaticImport.STATIC_IMPORT_CANDIDATE_MEMBERS.keySet())
@@ -33,7 +28,7 @@ final class StaticImportTest {
 
   @Test
   void identification() {
-    compilationTestHelper
+    CompilationTestHelper.newInstance(StaticImport.class, getClass())
         .addSourceLines(
             "A.java",
             "import static com.google.common.collect.ImmutableMap.toImmutableMap;",
@@ -118,7 +113,7 @@ final class StaticImportTest {
 
   @Test
   void replacement() {
-    refactoringTestHelper
+    BugCheckerRefactoringTestHelper.newInstance(StaticImport.class, getClass())
         .addInputLines(
             "A.java",
             "import static java.util.function.Predicate.not;",

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/StringCaseLocaleUsageTest.java

@@ -1,7 +1,5 @@
 package tech.picnic.errorprone.bugpatterns;
 
-import static com.google.errorprone.BugCheckerRefactoringTestHelper.newInstance;
-
 import com.google.errorprone.BugCheckerRefactoringTestHelper;
 import com.google.errorprone.BugCheckerRefactoringTestHelper.FixChoosers;
 import com.google.errorprone.BugCheckerRefactoringTestHelper.TestMode;
@@ -9,14 +7,9 @@ import com.google.errorprone.CompilationTestHelper;
 import org.junit.jupiter.api.Test;
 
 final class StringCaseLocaleUsageTest {
-  private final CompilationTestHelper compilationTestHelper =
-      CompilationTestHelper.newInstance(StringCaseLocaleUsage.class, getClass());
-  private final BugCheckerRefactoringTestHelper refactoringTestHelper =
-      newInstance(StringCaseLocaleUsage.class, getClass());
-
   @Test
   void identification() {
-    compilationTestHelper
+    CompilationTestHelper.newInstance(StringCaseLocaleUsage.class, getClass())
         .addSourceLines(
             "A.java",
             "import static java.util.Locale.ROOT;",
@@ -54,7 +47,7 @@ final class StringCaseLocaleUsageTest {
 
   @Test
   void replacementFirstSuggestedFix() {
-    refactoringTestHelper
+    BugCheckerRefactoringTestHelper.newInstance(StringCaseLocaleUsage.class, getClass())
         .setFixChooser(FixChoosers.FIRST)
         .addInputLines(
             "A.java",
@@ -93,7 +86,7 @@ final class StringCaseLocaleUsageTest {
 
   @Test
   void replacementSecondSuggestedFix() {
-    refactoringTestHelper
+    BugCheckerRefactoringTestHelper.newInstance(StringCaseLocaleUsage.class, getClass())
         .setFixChooser(FixChoosers.SECOND)
         .addInputLines(
             "A.java",

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/StringJoinTest.java

@@ -8,17 +8,12 @@ import com.google.errorprone.CompilationTestHelper;
 import org.junit.jupiter.api.Test;
 
 final class StringJoinTest {
-  private final CompilationTestHelper compilationHelper =
-      CompilationTestHelper.newInstance(StringJoin.class, getClass())
-          .expectErrorMessage(
-              "valueOf", containsPattern("Prefer `String#valueOf` over `String#format`"))
-          .expectErrorMessage("join", containsPattern("Prefer `String#join` over `String#format`"));
-  private final BugCheckerRefactoringTestHelper refactoringTestHelper =
-      BugCheckerRefactoringTestHelper.newInstance(StringJoin.class, getClass());
-
   @Test
   void identification() {
-    compilationHelper
+    CompilationTestHelper.newInstance(StringJoin.class, getClass())
+        .expectErrorMessage(
+            "valueOf", containsPattern("Prefer `String#valueOf` over `String#format`"))
+        .expectErrorMessage("join", containsPattern("Prefer `String#join` over `String#format`"))
         .addSourceLines(
             "A.java",
             "import java.util.Formattable;",
@@ -63,7 +58,7 @@ final class StringJoinTest {
 
   @Test
   void replacement() {
-    refactoringTestHelper
+    BugCheckerRefactoringTestHelper.newInstance(StringJoin.class, getClass())
         .addInputLines(
             "A.java",
             "class A {",

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/TimeZoneUsageTest.java

@@ -4,12 +4,9 @@ import com.google.errorprone.CompilationTestHelper;
 import org.junit.jupiter.api.Test;
 
 final class TimeZoneUsageTest {
-  private final CompilationTestHelper compilationHelper =
-      CompilationTestHelper.newInstance(TimeZoneUsage.class, getClass());
-
   @Test
   void identification() {
-    compilationHelper
+    CompilationTestHelper.newInstance(TimeZoneUsage.class, getClass())
         .addSourceLines(
             "A.java",
             "import static java.time.ZoneOffset.UTC;",

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/util/ConflictDetectionTest.java

@@ -0,0 +1,73 @@
+package tech.picnic.errorprone.bugpatterns.util;
+
+import static com.google.errorprone.BugPattern.SeverityLevel.ERROR;
+
+import com.google.errorprone.BugPattern;
+import com.google.errorprone.CompilationTestHelper;
+import com.google.errorprone.VisitorState;
+import com.google.errorprone.bugpatterns.BugChecker;
+import com.google.errorprone.bugpatterns.BugChecker.MethodTreeMatcher;
+import com.google.errorprone.matchers.Description;
+import com.google.errorprone.util.ASTHelpers;
+import com.sun.source.tree.MethodTree;
+import com.sun.tools.javac.code.Symbol.MethodSymbol;
+import org.junit.jupiter.api.Test;
+
+final class ConflictDetectionTest {
+  @Test
+  void matcher() {
+    CompilationTestHelper.newInstance(RenameBlockerFlagger.class, getClass())
+        .addSourceLines(
+            "pkg/A.java",
+            "package pkg;",
+            "",
+            "import static pkg.A.B.method3t;",
+            "",
+            "import pkg.A.method4t;",
+            "",
+            "class A {",
+            "  void method1() {",
+            "    method3t();",
+            "    method4(method4t.class);",
+            "  }",
+            "",
+            "  // BUG: Diagnostic contains: a method named `method2t` is already defined in this class or a",
+            "  // supertype",
+            "  void method2() {}",
+            "",
+            "  void method2t() {}",
+            "",
+            "  // BUG: Diagnostic contains: `method3t` is already statically imported",
+            "  void method3() {}",
+            "",
+            "  void method4(Object o) {}",
+            "",
+            "  // BUG: Diagnostic contains: `int` is not a valid identifier",
+            "  void in() {}",
+            "",
+            "  static class B {",
+            "    static void method3t() {}",
+            "  }",
+            "",
+            "  class method4t {}",
+            "}")
+        .doTest();
+  }
+
+  /**
+   * A {@link BugChecker} that uses {@link ConflictDetection#findMethodRenameBlocker(MethodSymbol,
+   * String, VisitorState)} to flag methods of which the name cannot be suffixed with a {@code t}.
+   */
+  @BugPattern(summary = "Interacts with `ConflictDetection` for testing purposes", severity = ERROR)
+  public static final class RenameBlockerFlagger extends BugChecker implements MethodTreeMatcher {
+    private static final long serialVersionUID = 1L;
+
+    @Override
+    public Description matchMethod(MethodTree tree, VisitorState state) {
+      return ConflictDetection.findMethodRenameBlocker(
+              ASTHelpers.getSymbol(tree), tree.getName() + "t", state)
+          .map(blocker -> buildDescription(tree).setMessage(blocker).build())
+          .orElse(Description.NO_MATCH);
+    }
+  }
+}

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/util/MethodMatcherFactoryTest.java

@@ -40,9 +40,6 @@ final class MethodMatcherFactoryTest {
                   "com.example.A#m2(java.lang.String)",
                   "com.example.sub.B#m3(int,int)"));
 
-  private final CompilationTestHelper compilationTestHelper =
-      CompilationTestHelper.newInstance(MatchedMethodsFlagger.class, getClass());
-
   @Test
   void createWithMalformedSignatures() {
     MethodMatcherFactory factory = new MethodMatcherFactory();
@@ -58,7 +55,7 @@ final class MethodMatcherFactoryTest {
 
   @Test
   void matcher() {
-    compilationTestHelper
+    CompilationTestHelper.newInstance(MatchedMethodsFlagger.class, getClass())
         .addSourceLines(
             "com/example/A.java",
             "package com.example;",

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/input/AssertJBigDecimalRulesTestInput.java

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refasterrules;
+package tech.picnic.errorprone.refasterrules.input;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.data.Offset.offset;

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/input/AssertJBigIntegerRulesTestInput.java

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refasterrules;
+package tech.picnic.errorprone.refasterrules.input;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.data.Offset.offset;

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/input/AssertJBooleanRulesTestInput.java

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refasterrules;
+package tech.picnic.errorprone.refasterrules.input;
 
 import static org.assertj.core.api.Assertions.assertThat;
 

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/input/AssertJByteRulesTestInput.java

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refasterrules;
+package tech.picnic.errorprone.refasterrules.input;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.data.Offset.offset;

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/input/AssertJCharSequenceRulesTestInput.java

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refasterrules;
+package tech.picnic.errorprone.refasterrules.input;
 
 import static org.assertj.core.api.Assertions.assertThat;
 

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/input/AssertJComparableRulesTestInput.java

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refasterrules;
+package tech.picnic.errorprone.refasterrules.input;
 
 import static org.assertj.core.api.Assertions.assertThat;
 

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/input/AssertJDoubleRulesTestInput.java

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refasterrules;
+package tech.picnic.errorprone.refasterrules.input;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.data.Offset.offset;

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/input/AssertJEnumerableRulesTestInput.java

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refasterrules;
+package tech.picnic.errorprone.refasterrules.input;
 
 import static org.assertj.core.api.Assertions.assertThat;
 

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/input/AssertJFloatRulesTestInput.java

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refasterrules;
+package tech.picnic.errorprone.refasterrules.input;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.data.Offset.offset;

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/input/AssertJIntegerRulesTestInput.java

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refasterrules;
+package tech.picnic.errorprone.refasterrules.input;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.data.Offset.offset;

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/input/AssertJLongRulesTestInput.java

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refasterrules;
+package tech.picnic.errorprone.refasterrules.input;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.data.Offset.offset;

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/input/AssertJMapRulesTestInput.java

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refasterrules;
+package tech.picnic.errorprone.refasterrules.input;
 
 import static org.assertj.core.api.Assertions.assertThat;
 

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/input/AssertJNumberRulesTestInput.java

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refasterrules;
+package tech.picnic.errorprone.refasterrules.input;
 
 import static org.assertj.core.api.Assertions.assertThat;
 

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/input/AssertJObjectRulesTestInput.java

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refasterrules;
+package tech.picnic.errorprone.refasterrules.input;
 
 import static org.assertj.core.api.Assertions.assertThat;
 

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/input/AssertJOptionalRulesTestInput.java

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refasterrules;
+package tech.picnic.errorprone.refasterrules.input;
 
 import static org.assertj.core.api.Assertions.assertThat;
 

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/input/AssertJPrimitiveRulesTestInput.java

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refasterrules;
+package tech.picnic.errorprone.refasterrules.input;
 
 import static org.assertj.core.api.Assertions.assertThat;
 

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/input/AssertJShortRulesTestInput.java

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refasterrules;
+package tech.picnic.errorprone.refasterrules.input;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.data.Offset.offset;

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/input/AssertJStringRulesTestInput.java

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refasterrules;
+package tech.picnic.errorprone.refasterrules.input;
 
 import static org.assertj.core.api.Assertions.assertThat;
 

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/input/AssertJThrowingCallableRulesTestInput.java

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refasterrules;
+package tech.picnic.errorprone.refasterrules.input;
 
 import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
 import static org.assertj.core.api.Assertions.assertThatIOException;

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/input/AssortedRulesTestInput.java

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refasterrules;
+package tech.picnic.errorprone.refasterrules.input;
 
 import static com.google.common.collect.ImmutableSet.toImmutableSet;
 

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/input/BigDecimalRulesTestInput.java

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refasterrules;
+package tech.picnic.errorprone.refasterrules.input;
 
 import com.google.common.collect.ImmutableSet;
 import java.math.BigDecimal;

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/input/CollectionRulesTestInput.java

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refasterrules;
+package tech.picnic.errorprone.refasterrules.input;
 
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableSet;

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/input/ComparatorRulesTestInput.java

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refasterrules;
+package tech.picnic.errorprone.refasterrules.input;
 
 import static java.util.Comparator.naturalOrder;
 import static java.util.Comparator.reverseOrder;

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/input/DoubleStreamRulesTestInput.java

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refasterrules;
+package tech.picnic.errorprone.refasterrules.input;
 
 import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.Streams;

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/input/EqualityRulesTestInput.java

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refasterrules;
+package tech.picnic.errorprone.refasterrules.input;
 
 import com.google.common.collect.BoundType;
 import com.google.common.collect.ImmutableSet;

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/input/ImmutableListMultimapRulesTestInput.java

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refasterrules;
+package tech.picnic.errorprone.refasterrules.input;
 
 import static com.google.common.collect.ImmutableListMultimap.flatteningToImmutableListMultimap;
 import static com.google.common.collect.ImmutableListMultimap.toImmutableListMultimap;

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/input/ImmutableListRulesTestInput.java

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refasterrules;
+package tech.picnic.errorprone.refasterrules.input;
 
 import static com.google.common.collect.ImmutableList.toImmutableList;
 import static java.util.Comparator.naturalOrder;

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/input/ImmutableMapRulesTestInput.java

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refasterrules;
+package tech.picnic.errorprone.refasterrules.input;
 
 import static com.google.common.collect.ImmutableMap.toImmutableMap;
 import static java.util.function.Function.identity;

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/input/ImmutableMultisetRulesTestInput.java

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refasterrules;
+package tech.picnic.errorprone.refasterrules.input;
 
 import static com.google.common.collect.ImmutableMultiset.toImmutableMultiset;
 

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/input/ImmutableSetMultimapRulesTestInput.java

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refasterrules;
+package tech.picnic.errorprone.refasterrules.input;
 
 import static com.google.common.collect.ImmutableSetMultimap.flatteningToImmutableSetMultimap;
 import static com.google.common.collect.ImmutableSetMultimap.toImmutableSetMultimap;