Introduce Dropwizard Metrics integration test (#1426)

.github/workflows/run-integration-tests.yml

@@ -1,9 +1,9 @@
 # If requested by means of a pull request comment, runs integration tests
 # against the project, using the code found on the pull request branch.
-# XXX: Generalize this to a matrix build of multiple integration tests,
-# possibly using multiple JDK or OS versions.
-# XXX: Investigate whether the comment can specify which integration tests run
-# run. See this example of a dynamic build matrix:
+# XXX: Review whether then build matrix should also vary JDK or OS versions.
+# XXX: Support `/integration-test [name...]` comment syntax to specify the
+# subset of integration tests to run.
+# See this example of a dynamic build matrix:
 # https://docs.github.com/en/actions/learn-github-actions/expressions#example-returning-a-json-object
 name: "Integration tests"
 on:
@@ -17,6 +17,9 @@ jobs:
     if: |
       github.event.issue.pull_request && contains(github.event.comment.body, '/integration-test')
     runs-on: ubuntu-24.04
+    strategy:
+      matrix:
+        integration-test: [ "checkstyle", "metrics" ]
     steps:
       - name: Install Harden-Runner
         uses: step-security/harden-runner@91182cccc01eb5e619899d80e4e971d6181294a7 # v2.10.1
@@ -26,6 +29,7 @@ jobs:
           allowed-endpoints: >
             api.adoptium.net:443
             checkstyle.org:443
+            example.com:80
             github.com:443
             objects.githubusercontent.com:443
             oss.sonatype.org:443
@@ -42,12 +46,12 @@ jobs:
       - name: Install project to local Maven repository
         run: mvn -T1C install -DskipTests -Dverification.skip
       - name: Run integration test
-        run: xvfb-run ./integration-tests/checkstyle.sh "${{ runner.temp }}/artifacts"
+        run: xvfb-run "./integration-tests/${{ matrix.integration-test }}.sh" "${{ runner.temp }}/artifacts"
       - name: Upload artifacts on failure
         if: ${{ failure() }}
         uses: actions/upload-artifact@b4b15b8c7c6ac21ea08fcf65892d2ee8f75cf882 # v4.4.3
         with:
-          name: integration-test-checkstyle
+          name: "integration-test-${{ matrix.integration-test }}"
           path: "${{ runner.temp }}/artifacts"
       - name: Remove installed project artifacts
         run: mvn dependency:purge-local-repository -DmanualInclude='${project.groupId}' -DresolutionFuzziness=groupId