diff --git a/apis/fluent-en_GB/atrium-api-fluent-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/fluent/en_GB/featureAssertions.kt b/apis/fluent-en_GB/atrium-api-fluent-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/fluent/en_GB/featureAssertions.kt
index 68142486d..f26049fa8 100644
--- a/apis/fluent-en_GB/atrium-api-fluent-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/fluent/en_GB/featureAssertions.kt
+++ b/apis/fluent-en_GB/atrium-api-fluent-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/fluent/en_GB/featureAssertions.kt
@@ -42,7 +42,8 @@ fun <T, R> Expect<T>.feature(
  * creates a new [Expect] for it and
  * returns it so that subsequent calls are based on the feature.
  *
- * @return The newly created [Expect] for the return value of calling [f] on the current subject of the assertion.
+ * @return The newly created [Expect] for the return value of calling the method [f]
+ *   on the current subject of the assertion.
  *
  * @since 0.9.0
  */
@@ -72,7 +73,8 @@ fun <T, R> Expect<T>.feature(
  * creates a new [Expect] for it and
  * returns it so that subsequent calls are based on the feature.
  *
- * @return The newly created [Expect] for the return value of calling [f] on the current subject of the assertion.
+ * @return The newly created [Expect] for the return value of calling the method [f]
+ *   on the current subject of the assertion.
  *
  * @since 0.9.0
  */
@@ -106,7 +108,8 @@ fun <T, A1, R> Expect<T>.feature(
  * creates a new [Expect] for it and
  * returns it so that subsequent calls are based on the feature.
  *
- * @return The newly created [Expect] for the return value of calling [f] on the current subject of the assertion.
+ * @return The newly created [Expect] for the return value of calling the method [f]
+ *   on the current subject of the assertion.
  *
  * @since 0.9.0
  */
@@ -140,7 +143,8 @@ fun <T, A1, A2, R> Expect<T>.feature(
  * creates a new [Expect] for it and
  * returns it so that subsequent calls are based on the feature.
  *
- * @return The newly created [Expect] for the return value of calling [f] on the current subject of the assertion.
+ * @return The newly created [Expect] for the return value of calling the method [f]
+ *   on the current subject of the assertion.
  *
  * @since 0.9.0
  */
@@ -174,7 +178,8 @@ fun <T, A1, A2, A3, R> Expect<T>.feature(
  * creates a new [Expect] for it and
  * returns it so that subsequent calls are based on the feature.
  *
- * @return The newly created [Expect] for the return value of calling [f] on the current subject of the assertion.
+ * @return The newly created [Expect] for the return value of calling the method [f]
+ *   on the current subject of the assertion.
  *
  * @since 0.9.0
  */
diff --git a/apis/fluent-en_GB/atrium-api-fluent-en_GB-common/src/test/kotlin/ch/tutteli/atrium/api/fluent/en_GB/Fun0AssertionsSpec.kt b/apis/fluent-en_GB/atrium-api-fluent-en_GB-common/src/test/kotlin/ch/tutteli/atrium/api/fluent/en_GB/Fun0AssertionsSpec.kt
index 504be460c..6ec6d3c08 100644
--- a/apis/fluent-en_GB/atrium-api-fluent-en_GB-common/src/test/kotlin/ch/tutteli/atrium/api/fluent/en_GB/Fun0AssertionsSpec.kt
+++ b/apis/fluent-en_GB/atrium-api-fluent-en_GB-common/src/test/kotlin/ch/tutteli/atrium/api/fluent/en_GB/Fun0AssertionsSpec.kt
@@ -4,21 +4,16 @@ import ch.tutteli.atrium.creating.Expect
 import ch.tutteli.atrium.specs.feature0
 import ch.tutteli.atrium.specs.feature1
 import ch.tutteli.atrium.specs.notImplemented
+import ch.tutteli.atrium.specs.withFeatureSuffix
 
 class Fun0AssertionsSpec : ch.tutteli.atrium.specs.integration.Fun0AssertionsSpec(
-    "toThrow" to Companion::toThrowFeature,
-    "toThrow" to Companion::toThrow,
+    ("toThrow" to ::toThrowFeature).withFeatureSuffix(),
+    "toThrow" to ::toThrow,
     feature0<() -> Int, Int>(Expect<() -> Int>::notToThrow),
     feature1<() -> Int, Expect<Int>.() -> Unit, Int>(Expect<() -> Int>::notToThrow),
     "⚬ ", "» "
 ) {
 
-    companion object {
-        fun toThrowFeature(expect: Expect<out () -> Any?>) = expect.toThrow<IllegalArgumentException>()
-        fun toThrow(expect: Expect<out () -> Any?>, assertionCreator: Expect<IllegalArgumentException>.() -> Unit) =
-            expect.toThrow<IllegalArgumentException> { assertionCreator() }
-    }
-
     @Suppress("unused", "UNUSED_VALUE", "UNUSED_VARIABLE")
     private fun ambiguityTest() {
         val a1: Expect<() -> Any?> = notImplemented()
@@ -37,3 +32,9 @@ class Fun0AssertionsSpec : ch.tutteli.atrium.specs.integration.Fun0AssertionsSpe
         val r8: Expect<Int> = a2.notToThrow {}
     }
 }
+
+private fun toThrowFeature(expect: Expect<out () -> Any?>) =
+    expect.toThrow<IllegalArgumentException>()
+
+private fun toThrow(expect: Expect<out () -> Any?>, assertionCreator: Expect<IllegalArgumentException>.() -> Unit) =
+    expect.toThrow<IllegalArgumentException> { assertionCreator() }
diff --git a/apis/fluent-en_GB/atrium-api-fluent-en_GB-common/src/test/kotlin/ch/tutteli/atrium/api/fluent/en_GB/IterableAllAssertionsSpec.kt b/apis/fluent-en_GB/atrium-api-fluent-en_GB-common/src/test/kotlin/ch/tutteli/atrium/api/fluent/en_GB/IterableAllAssertionsSpec.kt
index 760bb7016..46c1c7620 100644
--- a/apis/fluent-en_GB/atrium-api-fluent-en_GB-common/src/test/kotlin/ch/tutteli/atrium/api/fluent/en_GB/IterableAllAssertionsSpec.kt
+++ b/apis/fluent-en_GB/atrium-api-fluent-en_GB-common/src/test/kotlin/ch/tutteli/atrium/api/fluent/en_GB/IterableAllAssertionsSpec.kt
@@ -3,10 +3,11 @@ package ch.tutteli.atrium.api.fluent.en_GB
 import ch.tutteli.atrium.creating.Expect
 import ch.tutteli.atrium.specs.fun1
 import ch.tutteli.atrium.specs.notImplemented
+import ch.tutteli.atrium.specs.withNullableSuffix
 
 object IterableAllAssertionsSpec : ch.tutteli.atrium.specs.integration.IterableAllAssertionsSpec(
     fun1(Expect<Iterable<Double>>::all),
-    fun1(Expect<Iterable<Double?>>::all),
+    fun1(Expect<Iterable<Double?>>::all).withNullableSuffix(),
     "◆ ", "❗❗ ", "⚬ ", "» ", "▶ ", "◾ "
 ) {
     @Suppress("unused", "UNUSED_VALUE")
diff --git a/apis/fluent-en_GB/atrium-api-fluent-en_GB-common/src/test/kotlin/ch/tutteli/atrium/api/fluent/en_GB/MapAssertionsSpec.kt b/apis/fluent-en_GB/atrium-api-fluent-en_GB-common/src/test/kotlin/ch/tutteli/atrium/api/fluent/en_GB/MapAssertionsSpec.kt
index 867eda698..702158296 100644
--- a/apis/fluent-en_GB/atrium-api-fluent-en_GB-common/src/test/kotlin/ch/tutteli/atrium/api/fluent/en_GB/MapAssertionsSpec.kt
+++ b/apis/fluent-en_GB/atrium-api-fluent-en_GB-common/src/test/kotlin/ch/tutteli/atrium/api/fluent/en_GB/MapAssertionsSpec.kt
@@ -2,46 +2,26 @@ package ch.tutteli.atrium.api.fluent.en_GB
 
 import ch.tutteli.atrium.creating.Expect
 import ch.tutteli.atrium.domain.builders.utils.mapArguments
-import ch.tutteli.atrium.specs.fun0
-import ch.tutteli.atrium.specs.fun1
-import ch.tutteli.atrium.specs.fun2
-import ch.tutteli.atrium.specs.notImplemented
+import ch.tutteli.atrium.specs.*
+import kotlin.jvm.JvmName
 import kotlin.reflect.KFunction3
 
+private fun <K, V, T> mfun2(
+    f: KFunction3<Expect<Map<out K, V>>, Pair<K, T>, Array<out Pair<K, T>>, Expect<Map<out K, V>>>
+) = fun2(f)
+
 class MapAssertionsSpec : ch.tutteli.atrium.specs.integration.MapAssertionsSpec(
-    fun2<Map<out String, Int>, Pair<String, Int>, Array<out Pair<String, Int>>>(Expect<Map<out String, Int>>::contains),
-    fun2<Map<out String?, Int?>, Pair<String?, Int?>, Array<out Pair<String?, Int?>>>(Expect<Map<out String?, Int?>>::contains),
-    "${containsKeyWithValueAssertionsFun.name} ${KeyValue::class.simpleName}" to Companion::containsKeyValue,
-    "${containsKeyWithNullableValueAssertionsFun.name} ${KeyValue::class.simpleName}" to Companion::containsNullable,
+    mfun2<String, Int, Int>(Expect<Map<out String, Int>>::contains),
+    mfun2<String?, Int?, Int?>(Expect<Map<out String?, Int?>>::contains).withNullableSuffix(),
+    mfun2<String, Int, Expect<Int>.() -> Unit>(::contains).adjustName { "$it ${KeyValue::class.simpleName}" },
+    mfun2<String?, Int?, (Expect<Int>.() -> Unit)?>(::contains).adjustName { "$it ${KeyValue::class.simpleName}" }.withNullableSuffix(),
     fun1(Expect<Map<out String, *>>::containsKey),
-    fun1(Expect<Map<out String?, *>>::containsKey),
+    fun1(Expect<Map<out String?, *>>::containsKey).withNullableSuffix(),
     fun1(Expect<Map<out String, *>>::containsNotKey),
-    fun1(Expect<Map<out String?, *>>::containsNotKey),
+    fun1(Expect<Map<out String?, *>>::containsNotKey).withNullableSuffix(),
     fun0(Expect<Map<*, *>>::isEmpty),
     fun0(Expect<Map<*, *>>::isNotEmpty)
 ) {
-    companion object {
-        //@formatter:off
-        private val containsKeyWithValueAssertionsFun : KFunction3<Expect<Map<out String, Int>>, KeyValue<String, Int>, Array<out KeyValue<String, Int>>, Expect<Map<out String, Int>>> = Expect<Map<out String, Int>>::contains
-        private val containsKeyWithNullableValueAssertionsFun : KFunction3<Expect<Map<out String?, Int?>>, KeyValue<String?, Int>, Array<out KeyValue<String?, Int>>, Expect<Map<out String?, Int?>>> = Expect<Map<out String?, Int?>>::contains
-        //@formatter:on
-
-        fun containsKeyValue(
-            expect: Expect<Map<out String, Int>>,
-            keyValue: Pair<String, Expect<Int>.() -> Unit>,
-            otherKeyValues: Array<out Pair<String, Expect<Int>.() -> Unit>>
-        ) = mapArguments(keyValue, otherKeyValues).to { KeyValue(it.first, it.second) }.let { (first, others) ->
-            expect.contains(first, *others)
-        }
-
-        fun containsNullable(
-            expect: Expect<Map<out String?, Int?>>,
-            keyValue: Pair<String?, (Expect<Int>.() -> Unit)?>,
-            otherKeyValues: Array<out Pair<String?, (Expect<Int>.() -> Unit)?>>
-        ) = mapArguments(keyValue, otherKeyValues).to { KeyValue(it.first, it.second) }.let { (first, others) ->
-            expect.contains(first, *others)
-        }
-    }
 
     @Suppress("unused", "UNUSED_VALUE")
     private fun ambiguityTest() {
@@ -208,3 +188,20 @@ class MapAssertionsSpec : ch.tutteli.atrium.specs.integration.MapAssertionsSpec(
 
     }
 }
+
+private fun contains(
+    expect: Expect<Map<out String, Int>>,
+    keyValue: Pair<String, Expect<Int>.() -> Unit>,
+    otherKeyValues: Array<out Pair<String, Expect<Int>.() -> Unit>>
+) = mapArguments(keyValue, otherKeyValues).to { KeyValue(it.first, it.second) }.let { (first, others) ->
+    expect.contains(first, *others)
+}
+
+@JvmName("containsNullable")
+private fun contains(
+    expect: Expect<Map<out String?, Int?>>,
+    keyValue: Pair<String?, (Expect<Int>.() -> Unit)?>,
+    otherKeyValues: Array<out Pair<String?, (Expect<Int>.() -> Unit)?>>
+) = mapArguments(keyValue, otherKeyValues).to { KeyValue(it.first, it.second) }.let { (first, others) ->
+    expect.contains(first, *others)
+}
diff --git a/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/anyAssertions.kt b/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/anyAssertions.kt
index 23b0b10c2..093148973 100644
--- a/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/anyAssertions.kt
+++ b/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/anyAssertions.kt
@@ -171,10 +171,11 @@ inline infix fun <T> Expect<T>.and(@Suppress("UNUSED_PARAMETER") o: o): Expect<T
  *
  * @return An [Expect] for the current subject of the assertion.
  */
-infix fun <T> Expect<T>.and(assertionCreator: Expect<T>.() -> Unit) = addAssertionsCreatedBy(assertionCreator)
+infix fun <T> Expect<T>.and(assertionCreator: Expect<T>.() -> Unit): Expect<T> =
+    addAssertionsCreatedBy(assertionCreator)
 
 /**
- * Inline property referring actually to `this` and allows to write nicer sub-assertions.
+ * Inline property referring actually to `this` and allows to write infix assertions within an assertion group block
  *
  * For instance, instead of:
  * ```
diff --git a/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/creating/feature/Feature.kt b/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/creating/feature/Feature.kt
new file mode 100644
index 000000000..caa8a9d4f
--- /dev/null
+++ b/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/creating/feature/Feature.kt
@@ -0,0 +1,18 @@
+package ch.tutteli.atrium.api.infix.en_GB.creating.feature
+
+import kotlin.reflect.KProperty1
+
+/**
+ * Parameter object which contains a [description] of a feature along with an [extractor]
+ * which actually extracts the feature out of a subject of an assertion.
+ *
+ * Use `of(K..., ...) { ... }` to create this representation where the first argument is the extractor in form of a
+ * [KProperty1] or a `KFunctionX` and the remaining arguments are the required arguments in case of a `KFunctionX`
+ * where `X` > 1.
+ *
+ * @property description The description of the feature.
+ * @property extractor The extractor which extracts the feature out of the subject of the assertion.
+
+ * @since 0.10.0
+ */
+data class Feature<T, R>(val description: String, val extractor: (T) -> R)
diff --git a/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/creating/feature/FeatureWithCreator.kt b/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/creating/feature/FeatureWithCreator.kt
new file mode 100644
index 000000000..3aeddb1ce
--- /dev/null
+++ b/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/creating/feature/FeatureWithCreator.kt
@@ -0,0 +1,25 @@
+package ch.tutteli.atrium.api.infix.en_GB.creating.feature
+
+import ch.tutteli.atrium.creating.Expect
+import kotlin.reflect.KProperty1
+
+/**
+ * Parameter object which contains a [description] of a feature along with an [extractor]
+ * which actually extracts the feature out of a subject of an assertion + an [assertionCreator]
+ * which defines assertions for the feature.
+ *
+ * Use `of(K..., ...) { ... }` to create this representation where the first argument is the extractor in form of a
+ * [KProperty1] or a `KFunctionX`, the last an [assertionCreator]-lambda and the remaining arguments in-between the
+ * required arguments in case of a `KFunctionX` where `X` > 1.
+ *
+ * @property description The description of the feature.
+ * @property extractor The extractor which extracts the feature out of the subject of the assertion.
+ * @property assertionCreator The `assertionCreator`-lambda which defines assertions for the feature.
+ *
+ * @since 0.10.0
+ */
+data class FeatureWithCreator<T, R>(
+    val description: String,
+    val extractor: (T) -> R,
+    val assertionCreator: Expect<R>.() -> Unit
+)
diff --git a/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/creating/feature/MetaFeatureOptionWithCreator.kt b/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/creating/feature/MetaFeatureOptionWithCreator.kt
new file mode 100644
index 000000000..4b8097530
--- /dev/null
+++ b/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/creating/feature/MetaFeatureOptionWithCreator.kt
@@ -0,0 +1,22 @@
+package ch.tutteli.atrium.api.infix.en_GB.creating.feature
+
+import ch.tutteli.atrium.creating.Expect
+import ch.tutteli.atrium.domain.builders.creating.MetaFeatureOption
+import ch.tutteli.atrium.domain.creating.MetaFeature
+
+/**
+ * Parameter object which combines a lambda with a [MetaFeatureOption] receiver (called [provider])
+ * and an [assertionCreator].
+ *
+ * Use the function `of({ ... }) { ... }` to create this representation where the first
+ * argument is a lambda with a [MetaFeatureOption] as receiver which has to create a [MetaFeature]
+ * where the subject of the assertion is available via implicit parameter `it`.
+ * Usually you use [f][MetaFeatureOption.f] to create a [MetaFeature],
+ * e.g. `feature of({ f(it::size) }) { o toBe 3 }`
+ *
+ * @since 0.10.0
+ */
+data class MetaFeatureOptionWithCreator<T, R>(
+    val provider: MetaFeatureOption<T>.(T) -> MetaFeature<R>,
+    val assertionCreator: Expect<R>.() -> Unit
+)
diff --git a/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/creating/list/IndexWithCreator.kt b/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/creating/list/IndexWithCreator.kt
new file mode 100644
index 000000000..efb18670a
--- /dev/null
+++ b/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/creating/list/IndexWithCreator.kt
@@ -0,0 +1,14 @@
+package ch.tutteli.atrium.api.infix.en_GB.creating.list
+
+import ch.tutteli.atrium.creating.Expect
+
+
+/**
+ *  Parameter object which combines an [index] of type [Int] with an [assertionCreator] which defines assertions for
+ *  a resulting feature of type [E].
+ *
+ *  Use the function `index(Int) { ... }` to create this representation.
+ *
+ *  @since 0.10.0
+ */
+data class IndexWithCreator<E>(val index: Int, val assertionCreator: Expect<E>.() -> Unit)
diff --git a/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/creating/list/get/builders/ListGetStep.kt b/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/creating/list/get/builders/ListGetStep.kt
deleted file mode 100644
index 07cdea536..000000000
--- a/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/creating/list/get/builders/ListGetStep.kt
+++ /dev/null
@@ -1,40 +0,0 @@
-package ch.tutteli.atrium.api.infix.en_GB.creating.list.get.builders
-
-import ch.tutteli.atrium.api.infix.en_GB.creating.list.get.builders.impl.ListGetStepImpl
-import ch.tutteli.atrium.creating.Expect
-
-/**
- * Represents the extension point for another step after a `get index`-step within a
- * sophisticated `get` assertion building process for [List].
- *
- * @param E The element type of the [List].
- * @param T A subtype of [List].
- */
-interface ListGetStep<E, T : List<E>> {
-    /**
-     * The [Expect] for which this assertion is created
-     */
-    val expect: Expect<T>
-
-    /**
-     * The given index which will be used to perform the [List.get].
-     */
-    val index: Int
-
-    /**
-     * Makes the assertion that the given [index] is within the bounds of [Expect.subject] and that
-     * the corresponding entry holds all assertions the given [assertionCreator] might create for it.
-     *
-     * @return An [Expect] for the current subject of the assertion.
-     * @throws AssertionError Might throw an [AssertionError] if a created [Expect]s (by calling [assertionCreator])
-     *   does not hold.
-     * @throws IllegalArgumentException in case the given [assertionCreator] did not create a single assertion.
-     */
-    infix fun assertIt(assertionCreator: Expect<E>.() -> Unit): Expect<T>
-
-    companion object {
-        fun <E, T : List<E>> create(expect: Expect<T>, index: Int): ListGetStep<E, T> =
-            ListGetStepImpl(expect, index)
-    }
-}
-
diff --git a/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/creating/list/get/builders/impl/ListGetStepImpl.kt b/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/creating/list/get/builders/impl/ListGetStepImpl.kt
deleted file mode 100644
index b837b17d0..000000000
--- a/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/creating/list/get/builders/impl/ListGetStepImpl.kt
+++ /dev/null
@@ -1,14 +0,0 @@
-package ch.tutteli.atrium.api.infix.en_GB.creating.list.get.builders.impl
-
-import ch.tutteli.atrium.api.infix.en_GB.creating.list.get.builders.ListGetStep
-import ch.tutteli.atrium.creating.Expect
-import ch.tutteli.atrium.domain.builders.ExpectImpl
-
-internal class ListGetStepImpl<E, T: List<E>>(
-    override val expect: Expect<T>,
-    override val index: Int
-) : ListGetStep<E, T> {
-
-    override infix fun assertIt(assertionCreator: Expect<E>.() -> Unit): Expect<T>
-        = expect.addAssertion(ExpectImpl.list.get(expect, index).collect(assertionCreator))
-}
diff --git a/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/creating/map/KeyWithCreator.kt b/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/creating/map/KeyWithCreator.kt
new file mode 100644
index 000000000..853472d2d
--- /dev/null
+++ b/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/creating/map/KeyWithCreator.kt
@@ -0,0 +1,14 @@
+package ch.tutteli.atrium.api.infix.en_GB.creating.map
+
+import ch.tutteli.atrium.creating.Expect
+
+/**
+ *  Parameter object which combines an [key] of type [K] with an [assertionCreator] which defines assertions for
+ *  a resulting feature of type [V].
+ *
+ *  Use the function `key(...) { ... }` to create this representation where the first parameter corresponds
+ *  to the [key] and the second is the [assertionCreator]
+ *
+ *  @since 0.10.0
+ */
+data class KeyWithCreator<out K, V>(val key: K, val assertionCreator: Expect<V>.() -> Unit)
diff --git a/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/creating/map/get/builders/MapGetOption.kt b/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/creating/map/get/builders/MapGetOption.kt
deleted file mode 100644
index 179fb375b..000000000
--- a/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/creating/map/get/builders/MapGetOption.kt
+++ /dev/null
@@ -1,47 +0,0 @@
-package ch.tutteli.atrium.api.infix.en_GB.creating.map.get.builders
-
-import ch.tutteli.atrium.api.infix.en_GB.creating.map.get.builders.impl.MapGetOptionImpl
-import ch.tutteli.atrium.assertions.Assertion
-import ch.tutteli.atrium.creating.AssertionPlant
-import ch.tutteli.atrium.creating.Expect
-import ch.tutteli.atrium.creating.SubjectProvider
-
-/**
- * Represents the extension point for another option after a `get key`-step within a
- * sophisticated `get` assertion building process for [Map].
- *
- * @param K The key type of the [Map].
- * @param V the value type of the [Map].
- * @param T A subtype of [Map].
- */
-interface MapGetOption<K, V, T : Map<out K, V>> {
-    /**
-     * The [AssertionPlant] for which this assertion is created
-     */
-    val expect: Expect<T>
-
-    /**
-     * The given key which will be used to perform the [Map.get].
-     */
-    val key: K
-
-    /**
-     * Makes the assertion that the [Assert.subject][SubjectProvider.subject] contains the previously specified [key] and that the
-     * corresponding value holds all assertions the given [assertionCreator] might create for it.
-     *
-     * @return This expect to support a fluent API.
-     * @throws AssertionError Might throw an [AssertionError] if a created [Assertion]s (by calling [assertionCreator])
-     * does not hold.
-     * @throws IllegalArgumentException in case the given [assertionCreator] did not create a single assertion.
-     */
-    infix fun assertIt(assertionCreator: Expect<V>.() -> Unit): Expect<T>
-
-    companion object {
-        /**
-         * Creates a [MapGetOption] based on the given [expect] and [key].
-         */
-        fun <K, V, T : Map<out K, V>> create(expect: Expect<T>, key: K): MapGetOption<K, V, T> =
-            MapGetOptionImpl(expect, key)
-    }
-}
-
diff --git a/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/creating/map/get/builders/impl/MapGetOptionImpl.kt b/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/creating/map/get/builders/impl/MapGetOptionImpl.kt
deleted file mode 100644
index ae34f177f..000000000
--- a/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/creating/map/get/builders/impl/MapGetOptionImpl.kt
+++ /dev/null
@@ -1,14 +0,0 @@
-package ch.tutteli.atrium.api.infix.en_GB.creating.map.get.builders.impl
-
-import ch.tutteli.atrium.api.infix.en_GB.creating.map.get.builders.MapGetOption
-import ch.tutteli.atrium.creating.Expect
-import ch.tutteli.atrium.domain.builders.ExpectImpl
-
-internal class MapGetOptionImpl<K, V, T : Map<out K, V>>(
-    override val expect: Expect<T>,
-    override val key: K
-) : MapGetOption<K, V, T> {
-
-    override infix fun assertIt(assertionCreator: Expect<V>.() -> Unit): Expect<T> =
-        expect.addAssertion(ExpectImpl.map.getExisting(expect, key).collect(assertionCreator))
-}
diff --git a/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/featureAssertions.kt b/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/featureAssertions.kt
new file mode 100644
index 000000000..dfe813e4d
--- /dev/null
+++ b/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/featureAssertions.kt
@@ -0,0 +1,231 @@
+package ch.tutteli.atrium.api.infix.en_GB
+
+import ch.tutteli.atrium.api.infix.en_GB.creating.feature.Feature
+import ch.tutteli.atrium.api.infix.en_GB.creating.feature.FeatureWithCreator
+import ch.tutteli.atrium.api.infix.en_GB.creating.feature.MetaFeatureOptionWithCreator
+import ch.tutteli.atrium.assertions.AssertionGroup
+import ch.tutteli.atrium.creating.Expect
+import ch.tutteli.atrium.creating.FeatureExpect
+import ch.tutteli.atrium.domain.builders.ExpectImpl
+import ch.tutteli.atrium.domain.builders.creating.MetaFeatureOption
+import ch.tutteli.atrium.domain.creating.MetaFeature
+import kotlin.reflect.*
+
+/**
+ * Extracts the [property] out of the current subject of the assertion,
+ * creates a new [Expect] for it and
+ * returns it so that subsequent calls are based on the feature.
+ *
+ * @return The newly created [Expect] for the given [property].
+ *
+ * @since 0.10.0
+ */
+infix fun <T, R> Expect<T>.feature(property: KProperty1<T, R>): FeatureExpect<T, R> =
+    ExpectImpl.feature.property(this, property).getExpectOfFeature()
+
+/**
+ * Extracts the value which is returned when calling the method [f] on the current subject of the assertion,
+ * creates a new [Expect] for it and
+ * returns it so that subsequent calls are based on the feature.
+ *
+ * Use `feature of(...)` in case the method requires parameters or in case you want to define
+ * an assertion group block for it.
+ *
+ * @return The newly created [Expect] for the return value of calling the method [f]
+ *   on the current subject of the assertion.
+ *
+ * @since 0.10.0
+ */
+infix fun <T, R> Expect<T>.feature(f: KFunction1<T, R>): FeatureExpect<T, R> =
+    ExpectImpl.feature.f0(this, f).getExpectOfFeature()
+
+/**
+ * Extracts a feature out of the current subject of the assertion using the given [Feature.extractor],
+ * creates a new [Expect] for it and
+ * returns it so that subsequent calls are based on the feature.
+ *
+ * Use `of(K..., ...)` to create a [Feature] where the first argument is the extractor in form of a
+ *   [KProperty1] or a `KFunctionX` and potentially the required arguments for a `KFunctionX` where `X` > 1.
+ *
+ * @param of Use `of(K..., ...)` to create a [Feature] where the first argument is the extractor in form of a
+ *   [KProperty1] or a `KFunctionX` and potentially the required arguments for a `KFunctionX` where `X` > 1.
+ *
+ * @return The newly created [Expect] for the extracted feature.
+ *
+ * @since 0.10.0
+ */
+infix fun <T, R> Expect<T>.feature(of: Feature<T, R>): FeatureExpect<T, R> =
+    ExpectImpl.feature.manualFeature(this, of.description, of.extractor).getExpectOfFeature()
+
+/**
+ * Extracts a feature out of the current subject of the assertion using the given [FeatureWithCreator.extractor],
+ * creates a new [Expect] for it,
+ * applies an assertion group based on the given [FeatureWithCreator.assertionCreator] for the feature and
+ * returns the initial [Expect] with the current subject.
+ *
+ * Use `of(K..., ...) { ... }` to create a [FeatureWithCreator] where the first argument is the extractor in
+ *   form of a [KProperty1] or a `KFunctionX`, the last an `assertionCreator`-lambda and the remaining arguments
+ *   in-between the required arguments in case of a `KFunctionX` where `X` > 1.
+ *
+ * @param of Use `of(K..., ...) { ... }` to create a [FeatureWithCreator] where the first argument is the extractor in
+ *   form of a [KProperty1] or a `KFunctionX`, the last an `assertionCreator`-lambda and the remaining arguments
+ *   in-between the required arguments in case of a `KFunctionX` where `X` > 1.
+ *
+ * @return An [Expect] for the current subject of the assertion.
+ * @throws AssertionError Might throw an [AssertionError] in case the created [AssertionGroup] does not hold.
+ *
+ * @since 0.10.0
+ */
+infix fun <T, R> Expect<T>.feature(of: FeatureWithCreator<T, R>): Expect<T> =
+    ExpectImpl.feature.manualFeature(this, of.description, of.extractor).addToInitial(of.assertionCreator)
+
+
+/**
+ * Extracts a feature out of the current subject of the assertion,
+ * based on the given [provider],
+ * creates a new [Expect] for it and
+ * returns it so that subsequent calls are based on the feature.
+ *
+ * @param provider Creates a [MetaFeature] where the subject of the assertion is available via
+ *   implicit parameter `it`. Usually you use [f][MetaFeatureOption.f] to create a [MetaFeature],
+ *   e.g. `feature { f(it::size) }`
+ *
+ * @return The newly created [Expect] for the extracted feature.
+ *
+ * @since 0.10.0
+ */
+infix fun <T, R> Expect<T>.feature(provider: MetaFeatureOption<T>.(T) -> MetaFeature<R>): FeatureExpect<T, R> =
+    ExpectImpl.feature.genericSubjectBasedFeature(this) { MetaFeatureOption(this).provider(it) }.getExpectOfFeature()
+
+/**
+ * Extracts a feature out of the current subject of the assertion,
+ * based on the given [MetaFeatureOptionWithCreator]
+ * creates a new [Expect] for it,
+ * applies an assertion group based on the given [MetaFeatureOptionWithCreator.assertionCreator] for the feature and
+ * returns the initial [Expect] with the current subject.
+ *
+ * Note that you need to enable the new type inference of Kotlin (or use Kotlin 1.4 and above) in order that Kotlin
+ * is able to infer the types.
+ * As workaround you can use the overload which expects `MetaFeatureOption<T>.(T) -> MetaFeature<R>`
+ * and use `it` after the call (import from the package workaround). For instance:
+ *
+ * ```
+ * // use
+ * expect(person) feature { f(it::age) } it { o toBe 20 }
+ *
+ * // instead of (which causes problems with Kotlin < 1.4)
+ * expect(person) feature of({ f(it::age) }) { o toBe 20 }
+ * ```
+ *
+ * @param of Use the function `of({ ... }) { ... }` to create the [MetaFeatureOptionWithCreator] where the first
+ *   argument is a lambda with a [MetaFeatureOption] as receiver which has to create a [MetaFeature]
+ *   where the subject of the assertion is available via implicit parameter `it`.
+ *   Usually you use [f][MetaFeatureOption.f] to create a [MetaFeature],
+ *   e.g. `feature of({ f(it::size) }) { o toBe 3 }`
+ *
+ * @return An [Expect] for the current subject of the assertion.
+ * @since 0.10.0
+ */
+infix fun <T, R> Expect<T>.feature(of: MetaFeatureOptionWithCreator<T, R>): Expect<T> =
+    ExpectImpl.feature.genericSubjectBasedFeature(this) {
+        MetaFeatureOption(this).(of.provider)(it)
+    }.addToInitial(of.assertionCreator)
+
+/**
+ * Creates a [MetaFeature] using the given [provider] and [description].
+ *
+ * This can be used to create complex features with a custom description or as workaround where Kotlin is not able to
+ * infer the types properly.
+ *
+ * For instance:
+ * ```
+ * expect(person) feature { f("first underage child", it.children.first { it < 18 }) }
+ * ```
+ *
+ * @return The newly created [MetaFeature].
+ */
+@Suppress("unused" /* unused receiver, but that's fine */)
+fun <T, R> MetaFeatureOption<T>.f(description: String, provider: R): MetaFeature<R> =
+    MetaFeature(description, provider)
+
+//@formatter:off
+/**
+ * Helper function to create a [Feature] based on a [KFunction2] + arguments.
+ */
+fun <T, A1, R> of(f: KFunction2<T, A1, R>, a1: A1): Feature<T, R> =
+    Feature(f.name) { f.invoke(it, a1) }
+
+/**
+ * Helper function to create a [Feature] based on a [KFunction3] + arguments.
+ */
+fun <T, A1, A2, R > of(f: KFunction3<T, A1, A2, R>, a1: A1, a2: A2): Feature<T, R> =
+     Feature(f.name) { f.invoke(it, a1, a2) }
+
+/**
+ * Helper function to create a [Feature] based on a [KFunction4] + arguments.
+ */
+fun <T, A1, A2, A3, R> of(f:  KFunction4<T, A1, A2, A3, R>, a1: A1, a2: A2, a3: A3): Feature<T, R> =
+     Feature(f.name) { f.invoke(it, a1, a2, a3) }
+
+/**
+ * Helper function to create a [Feature] based on a [KFunction5] + arguments.
+ */
+fun <T, A1, A2, A3, A4, R> of(f: KFunction5<T, A1, A2, A3, A4, R>, a1: A1, a2: A2, a3: A3, a4: A4): Feature<T, R> =
+     Feature(f.name) { f.invoke(it, a1, a2, a3, a4) }
+
+/**
+ * Helper function to create a [Feature] based on a [KFunction5] + arguments.
+ */
+fun <T, A1, A2, A3, A4, A5, R> of(f: KFunction6<T, A1, A2, A3, A4, A5, R>, a1: A1, a2: A2, a3: A3, a4: A4, a5: A5): Feature<T, R> =
+    Feature(f.name) { f.invoke(it, a1, a2, a3, a4, a5) }
+
+/**
+ * Helper function to create a [FeatureWithCreator] based on a [KProperty1] + [assertionCreator].
+ */
+fun <T, R> of(property: KProperty1<T, R>, assertionCreator: Expect<R>.() -> Unit): FeatureWithCreator<T, R> =
+    FeatureWithCreator(property.name, { property.invoke(it) }, assertionCreator)
+
+/**
+ * Helper function to create a [FeatureWithCreator] based on a [KFunction1] + [assertionCreator].
+ */
+fun <T, R> of(f: KFunction1<T, R>, assertionCreator: Expect<R>.() -> Unit): FeatureWithCreator<T, R> =
+    FeatureWithCreator(f.name, { f.invoke(it) }, assertionCreator)
+
+/**
+ * Helper function to create a [FeatureWithCreator] based on a [KFunction2] + arguments + [assertionCreator].
+ */
+fun <T, A1, R> of(f: KFunction2<T, A1, R>, a1: A1, assertionCreator: Expect<R>.() -> Unit): FeatureWithCreator<T, R> =
+    FeatureWithCreator(f.name, { f.invoke(it, a1) }, assertionCreator)
+
+/**
+ * Helper function to create a [FeatureWithCreator] based on a [KFunction3] + arguments + [assertionCreator].
+ */
+fun <T, A1, A2, R > of(f: KFunction3<T, A1, A2, R>, a1: A1, a2: A2, assertionCreator: Expect<R>.() -> Unit): FeatureWithCreator<T, R> =
+     FeatureWithCreator(f.name, { f.invoke(it, a1, a2) }, assertionCreator)
+
+/**
+ * Helper function to create a [FeatureWithCreator] based on a [KFunction4] + arguments + [assertionCreator].
+ */
+fun <T, A1, A2, A3, R> of(f: KFunction4<T, A1, A2, A3, R>, a1: A1, a2: A2, a3: A3, assertionCreator: Expect<R>.() -> Unit): FeatureWithCreator<T, R> =
+     FeatureWithCreator(f.name, { f.invoke(it, a1, a2, a3) }, assertionCreator)
+
+/**
+ * Helper function to create a [FeatureWithCreator] based on a [KFunction5] + arguments + [assertionCreator].
+ */
+fun <T, A1, A2, A3, A4, R> of(f: KFunction5<T, A1, A2, A3, A4, R>, a1: A1, a2: A2, a3: A3, a4: A4, assertionCreator: Expect<R>.() -> Unit): FeatureWithCreator<T, R> =
+     FeatureWithCreator(f.name, { f.invoke(it, a1, a2, a3, a4) }, assertionCreator)
+//@formatter:on
+
+
+/**
+ * Helper function to create a [MetaFeatureOptionWithCreator] based on a lambda with
+ * [MetaFeatureOption] receiver (has to return a [MetaFeature])  and an [assertionCreator].
+ */
+fun <T, R> of(
+    provider: MetaFeatureOption<T>.(T) -> MetaFeature<R>,
+    assertionCreator: Expect<R>.() -> Unit
+): MetaFeatureOptionWithCreator<T, R> =
+    MetaFeatureOptionWithCreator(
+        provider,
+        assertionCreator
+    )
diff --git a/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/keywords.kt b/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/keywords.kt
index 8f1bbc3b9..e6b45b239 100644
--- a/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/keywords.kt
+++ b/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/keywords.kt
@@ -27,40 +27,48 @@ object Blank : Keyword
 
 /**
  * Represents the pseudo keyword `contain` as in [to] `contain`.
+ * It can be used for a parameter less function so that it has one parameter and thus can be used as infix function.
  */
 object contain : Keyword
 
 /**
  * Represents the pseudo keyword `case` as in [ignoring] `case`.
+ * It can be used for a parameter less function so that it has one parameter and thus can be used as infix function.
  */
 object case : Keyword
 
 /**
  * Represents the pseudo keyword `entries` as in [grouped] `entries`.
+ * It can be used for a parameter less function so that it has one parameter and thus can be used as infix function.
  */
 object entries : Keyword
 
 /**
  * Represents the pseudo keyword `group` as in [within] `group`.
+ * It can be used for a parameter less function so that it has one parameter and thus can be used as infix function.
  */
 object group : Keyword
 
 /**
  * Represents a filler, a pseudo keyword where there isn't really a good keyword.
- * A reader should skip this filler without reading it. For instance, `contains o atleast 1...` should be read as
+ * A reader should skip this filler without reading it. For instance, `contains o atLeast 1...` should be read as
  * `contains at least once...`
  *
+ * It can be used for a parameter less function so that it has one parameter and thus can be used as infix function.
+ *
  * @since 0.10.0
  */
 object o : Keyword
 
 /**
  * Represents the pseudo keyword `only` as in [and] `only`.
+ * It can be used for a parameter less function so that it has one parameter and thus can be used as infix function.
  */
 object only : Keyword
 
 /**
  * Represents the pseudo keyword `order` as in [inAny] `order`.
+ * It can be used for a parameter less function so that it has one parameter and thus can be used as infix function.
  */
 object order : Keyword
 
diff --git a/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/listAssertions.kt b/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/listAssertions.kt
index 01344b2d9..946d6e502 100644
--- a/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/listAssertions.kt
+++ b/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/listAssertions.kt
@@ -1,6 +1,6 @@
 package ch.tutteli.atrium.api.infix.en_GB
 
-import ch.tutteli.atrium.api.infix.en_GB.creating.list.get.builders.ListGetStep
+import ch.tutteli.atrium.api.infix.en_GB.creating.list.IndexWithCreator
 import ch.tutteli.atrium.creating.Expect
 import ch.tutteli.atrium.domain.builders.ExpectImpl
 
@@ -9,15 +9,26 @@ import ch.tutteli.atrium.domain.builders.ExpectImpl
  * returns an [Expect] for the element at that position.
  *
  * @return The newly created [Expect] for the element at position [index].
- * @throws AssertionError if the given [index] is out of bound.
+ * @throws AssertionError Might throw an [AssertionError] if the given [index] is out of bound.
  */
 infix fun <E, T : List<E>> Expect<T>.get(index: Int): Expect<E> =
     ExpectImpl.list.get(this, index).getExpectOfFeature()
 
 /**
- * Prepares the assertion about the return value of calling [get][List.get] with the given [index].
+ * Expects that the given [index][IndexWithCreator.index] is within the bounds of the subject of the assertion
+ * (a [List]) and that the element at that position holds all assertions the given
+ * [IndexWithCreator.assertionCreator] creates for it.
  *
- * @return A fluent builder to finish the assertion.
+ *  Use the function `index(Int) { ... }` to create an [IndexWithCreator].
+ *
+ * @return This assertion container to support a fluent API.
+ * @throws AssertionError Might throw an [AssertionError] if the given [index] is out of bound or
+ *   if the assertion made is not correct.
  */
-infix fun <E, T : List<E>> Expect<T>.get(index: Index): ListGetStep<E, T> =
-    ListGetStep.create(this, index.index)
+infix fun <E, T : List<E>> Expect<T>.get(index: IndexWithCreator<E>): Expect<T> =
+    ExpectImpl.list.get(this, index.index).addToInitial(index.assertionCreator)
+
+/**
+ * Helper function to create an [IndexWithCreator] based on the given [index] and [assertionCreator].
+ */
+fun <E> index(index: Int, assertionCreator: Expect<E>.() -> Unit) = IndexWithCreator(index, assertionCreator)
diff --git a/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/mapAssertions.kt b/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/mapAssertions.kt
index 48f30c173..072a7c081 100644
--- a/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/mapAssertions.kt
+++ b/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/mapAssertions.kt
@@ -1,6 +1,7 @@
 package ch.tutteli.atrium.api.infix.en_GB
 
-import ch.tutteli.atrium.api.infix.en_GB.creating.map.get.builders.MapGetOption
+import ch.tutteli.atrium.api.infix.en_GB.creating.map.KeyWithCreator
+import ch.tutteli.atrium.assertions.Assertion
 import ch.tutteli.atrium.creating.Expect
 import ch.tutteli.atrium.domain.builders.ExpectImpl
 
@@ -87,12 +88,23 @@ infix fun <K, V, T : Map<out K, V>> Expect<T>.getExisting(key: K): Expect<V> =
     ExpectImpl.map.getExisting(this, key).getExpectOfFeature()
 
 /**
- * Prepares the assertion about the return value of calling [get][Map.get] with the given [key].
+ * Expects that the subject of the assertion (a [Map]) contains the given [key] and that
+ * the corresponding value holds all assertions the given [KeyWithCreator.assertionCreator] creates for it.
  *
- * @return A fluent builder to finish the assertion.
- * */
-infix fun <K, V, T : Map<out K, V>> Expect<T>.getExisting(key: Key<K>): MapGetOption<K, V, T> =
-    MapGetOption.create(this, key.key)
+ * @param key Use the function `key(...) { ... }` to create a [KeyWithCreator] where the first parameter corresponds
+ *  to the key and the second is the `assertionCreator`-lambda
+ *
+ * @return An [Expect] for the current subject of the assertion.
+ * @throws AssertionError Might throw an [AssertionError] the given [key] does not exist or
+ *   if the assertion made is not correct.
+ */
+infix fun <K, V, T : Map<out K, V>> Expect<T>.getExisting(key: KeyWithCreator<K, V>): Expect<T> =
+    ExpectImpl.map.getExisting(this, key.key).addToInitial(key.assertionCreator)
+
+/**
+ * Helper function to create an [KeyWithCreator] based on the given [key] and [assertionCreator].
+ */
+fun <K, V> key(key: K, assertionCreator: Expect<V>.() -> Unit) = KeyWithCreator(key, assertionCreator)
 
 
 /**
@@ -178,3 +190,4 @@ fun <K, V, T : Map<out K, V>> Expect<T>.asEntries(): Expect<Set<Map.Entry<K, V>>
 infix fun <K, V, T : Map<out K, V>> Expect<T>.asEntries(
     assertionCreator: Expect<Set<Map.Entry<K, V>>>.() -> Unit
 ): Expect<T> = apply { asEntries().addAssertionsCreatedBy(assertionCreator) }
+
diff --git a/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/parameterObjects.kt b/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/parameterObjects.kt
index ee945e498..aeb3f4cde 100644
--- a/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/parameterObjects.kt
+++ b/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/parameterObjects.kt
@@ -4,31 +4,24 @@ import ch.tutteli.atrium.creating.Expect
 import ch.tutteli.atrium.domain.builders.utils.VarArgHelper
 
 /**
- * Wrapper for a single index -- can be used as distinguishable type for an overload where Int is already in use.
- */
-data class Index(val index: Int)
-
-data class Key<out K>(val key: K)
-/**
- * Parameter object to express `T, vararg T` in the infix-api.
+ * Parameter object to express `T, vararg T`.
  */
 class All<out T>(override val expected: T, override vararg val otherExpected: T) : VarArgHelper<T>
 
 /**
- * Parameter object to express `Pair<K, V>, vararg Pair<K, V>` in the infix-api.
- */
-class Pairs<out K, out V>(
-    override val expected: Pair<K, V>,
-    override vararg val otherExpected: Pair<K, V>
-) : VarArgHelper<Pair<K, V>>
-
-
-/**
- * Parameter object to express a key/value [Pair] whose value type is a lambda with an
- * [Assert][AssertionPlant] receiver, which means one can either pass a lambda or `null`.
+ * Parameter object to express a key/value [Pair] whose value type is a nullable lambda with an
+ * [Expect] receiver, which means one can either pass a lambda or `null`.
  */
 data class KeyValue<out K, V : Any>(val key: K, val valueAssertionCreatorOrNull: (Expect<V>.() -> Unit)?) {
     fun toPair(): Pair<K, (Expect<V>.() -> Unit)?> = key to valueAssertionCreatorOrNull
     override fun toString(): String =
         "KeyValue(key=$key, value=${if (valueAssertionCreatorOrNull == null) "null" else "lambda"})"
 }
+
+/**
+ * Parameter object to express `Pair<K, V>, vararg Pair<K, V>`.
+ */
+class Pairs<out K, out V>(
+    override val expected: Pair<K, V>,
+    override vararg val otherExpected: Pair<K, V>
+) : VarArgHelper<Pair<K, V>>
diff --git a/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/sequenceAssertions.kt b/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/sequenceAssertions.kt
index 73e955711..63912e893 100644
--- a/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/sequenceAssertions.kt
+++ b/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/sequenceAssertions.kt
@@ -1,3 +1,5 @@
+package ch.tutteli.atrium.api.infix.en_GB
+
 import ch.tutteli.atrium.creating.Expect
 import ch.tutteli.atrium.domain.builders.ExpectImpl.changeSubject
 
@@ -9,8 +11,8 @@ import ch.tutteli.atrium.domain.builders.ExpectImpl.changeSubject
  *
  * @return The newly created [Expect] for the transformed subject.
  */
-fun <E, T : Sequence<E>> Expect<T>.asIterable(): Expect<Iterable<E>>
-    = changeSubject(this).unreported { it.asIterable() }
+fun <E, T : Sequence<E>> Expect<T>.asIterable(): Expect<Iterable<E>> =
+    changeSubject(this).unreported { it.asIterable() }
 
 /**
  * Expects that the subject of the assertion holds all assertions the given [assertionCreator] creates for
diff --git a/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/workaround/anyAssertions.kt b/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/workaround/anyAssertions.kt
new file mode 100644
index 000000000..2c0b63365
--- /dev/null
+++ b/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/main/kotlin/ch/tutteli/atrium/api/infix/en_GB/workaround/anyAssertions.kt
@@ -0,0 +1,25 @@
+package ch.tutteli.atrium.api.infix.en_GB.workaround
+
+import ch.tutteli.atrium.api.infix.en_GB.and
+import ch.tutteli.atrium.creating.Expect
+
+/**
+ * Can be used to create a group of sub assertions when using the fluent API.
+ *
+ * Intended to be used in combination with feature assertions where Kotlin < 1.4 is not able to infer the correct type.
+ * For instance:
+ * ```
+ * // use
+ * expect(person) feature { f(it::age) } it { o toBe 20 }
+ *
+ * // instead of (which causes problems with Kotlin < 1.4)
+ * expect(person) feature of({ f(it::age) }) { o toBe 20 }
+ * ```
+ *
+ * Note that this workaround will be removed in some minor version after a major version with Kotlin 1.4 support
+ * (most likely with Atrium v1.1.0 where Atrium v1.0.0 requires Kotlin 1.4)
+ *
+ * @return An [Expect] for the current subject of the assertion.
+ */
+@Suppress("NOTHING_TO_INLINE" /* inline so that one does not actually call `it` on binary level */)
+inline infix fun <T> Expect<T>.it(noinline assertionCreator: Expect<T>.() -> Unit): Expect<T> = and(assertionCreator)
diff --git a/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/test/kotlin/ch/tutteli/atrium/api/infix/en_GB/AnyAssertionsSpec.kt b/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/test/kotlin/ch/tutteli/atrium/api/infix/en_GB/AnyAssertionsSpec.kt
index b96d9c2d6..54338cc49 100644
--- a/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/test/kotlin/ch/tutteli/atrium/api/infix/en_GB/AnyAssertionsSpec.kt
+++ b/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/test/kotlin/ch/tutteli/atrium/api/infix/en_GB/AnyAssertionsSpec.kt
@@ -81,7 +81,7 @@ class AnyAssertionsSpec : ch.tutteli.atrium.specs.integration.AnyAssertionsSpec(
 
     //regression for #298, should compile without the need for E : Any or List<E?>
     @Suppress("unused")
-    fun <E> Expect<List<E>>.firstIs(value: E) = o get Index(0) assertIt { o toBe value }
+    fun <E> Expect<List<E>>.firstIs(value: E) = o get index(0) { o toBe value }
 }
 
 private fun toBeNull(expect: Expect<Int?>) = expect toBe null
diff --git a/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/test/kotlin/ch/tutteli/atrium/api/infix/en_GB/CollectionAssertionsSpec.kt b/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/test/kotlin/ch/tutteli/atrium/api/infix/en_GB/CollectionAssertionsSpec.kt
index a630924a9..ea4802747 100644
--- a/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/test/kotlin/ch/tutteli/atrium/api/infix/en_GB/CollectionAssertionsSpec.kt
+++ b/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/test/kotlin/ch/tutteli/atrium/api/infix/en_GB/CollectionAssertionsSpec.kt
@@ -6,7 +6,7 @@ import ch.tutteli.atrium.specs.testutils.WithAsciiReporter
 
 class CollectionAssertionsSpec : ch.tutteli.atrium.specs.integration.CollectionAssertionsSpec(
     "toBe ${Empty::class.simpleName}" to ::isEmpty,
-    "toBe ${Empty::class.simpleName}" to ::isNotEmpty
+    "notToBe ${Empty::class.simpleName}" to ::isNotEmpty
 ) {
     companion object : WithAsciiReporter()
 
@@ -28,5 +28,5 @@ class CollectionAssertionsSpec : ch.tutteli.atrium.specs.integration.CollectionA
     }
 }
 
-fun isEmpty(expect: Expect<Collection<Int>>) = expect toBe Empty
-fun isNotEmpty(expect: Expect<Collection<Int>>) = expect notToBe Empty
+private fun isEmpty(expect: Expect<Collection<Int>>) = expect toBe Empty
+private fun isNotEmpty(expect: Expect<Collection<Int>>) = expect notToBe Empty
diff --git a/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/test/kotlin/ch/tutteli/atrium/api/infix/en_GB/IterableAllAssertionsSpec.kt b/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/test/kotlin/ch/tutteli/atrium/api/infix/en_GB/IterableAllAssertionsSpec.kt
index 606753783..4fcbc4b91 100644
--- a/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/test/kotlin/ch/tutteli/atrium/api/infix/en_GB/IterableAllAssertionsSpec.kt
+++ b/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/test/kotlin/ch/tutteli/atrium/api/infix/en_GB/IterableAllAssertionsSpec.kt
@@ -1,15 +1,14 @@
 package ch.tutteli.atrium.api.infix.en_GB
 
-import ch.tutteli.atrium.specs.testutils.WithAsciiReporter
 import ch.tutteli.atrium.creating.Expect
 import ch.tutteli.atrium.specs.fun1
-import ch.tutteli.atrium.specs.name
 import ch.tutteli.atrium.specs.notImplemented
+import ch.tutteli.atrium.specs.testutils.WithAsciiReporter
 import ch.tutteli.atrium.specs.withNullableSuffix
 
 class IterableAllAssertionsSpec : ch.tutteli.atrium.specs.integration.IterableAllAssertionsSpec(
-    fun1(Expect<Iterable<Double>>::all).name to ::all,
-    fun1(Expect<Iterable<Double?>>::all).withNullableSuffix().name to ::allNullable,
+    fun1(Expect<Iterable<Double>>::all),
+    fun1(Expect<Iterable<Double?>>::all).withNullableSuffix(),
     "* ", "(!) ", "- ", "» ", ">> ", "=> "
 ) {
     companion object : WithAsciiReporter()
@@ -21,17 +20,11 @@ class IterableAllAssertionsSpec : ch.tutteli.atrium.specs.integration.IterableAl
 
         var star: Expect<Iterable<*>> = notImplemented()
 
-        a1 = a1.all {}
+        a1 = a1 all {}
 
-        a1b = a1b.all {}
-        a1b = a1b.all(null)
+        a1b = a1b all {}
+        a1b = a1b all null
 
-        star = star.all {}
+        star = star all {}
     }
 }
-
-private fun all(expect: Expect<Iterable<Double>>, assertionCreator: Expect<Double>.() -> Unit) =
-    expect all assertionCreator
-
-private fun allNullable(expect: Expect<Iterable<Double?>>, assertionCreator: (Expect<Double>.() -> Unit)?) =
-    expect all assertionCreator
diff --git a/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/test/kotlin/ch/tutteli/atrium/api/infix/en_GB/ListFeatureAssertionsSpec.kt b/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/test/kotlin/ch/tutteli/atrium/api/infix/en_GB/ListFeatureAssertionsSpec.kt
index f4fd936c2..4441ce7bc 100644
--- a/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/test/kotlin/ch/tutteli/atrium/api/infix/en_GB/ListFeatureAssertionsSpec.kt
+++ b/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/test/kotlin/ch/tutteli/atrium/api/infix/en_GB/ListFeatureAssertionsSpec.kt
@@ -1,18 +1,18 @@
 package ch.tutteli.atrium.api.infix.en_GB
 
-import ch.tutteli.atrium.api.infix.en_GB.creating.list.get.builders.ListGetStep
-import ch.tutteli.atrium.specs.testutils.WithAsciiReporter
 import ch.tutteli.atrium.creating.Expect
 import ch.tutteli.atrium.specs.feature1
+import ch.tutteli.atrium.specs.fun2
 import ch.tutteli.atrium.specs.notImplemented
+import ch.tutteli.atrium.specs.testutils.WithAsciiReporter
 import ch.tutteli.atrium.specs.withNullableSuffix
-import kotlin.reflect.KFunction2
+import kotlin.jvm.JvmName
 
 class ListFeatureAssertionsSpec : ch.tutteli.atrium.specs.integration.ListFeatureAssertionsSpec(
     feature1<List<Int>, Int, Int>(Expect<List<Int>>::get),
-    getIndexPair(),
+    fun2<List<Int>, Int, Expect<Int>.() -> Unit>(::get),
     feature1<List<Int?>, Int, Int?>(Expect<List<Int?>>::get).withNullableSuffix(),
-    getIndexNullablePair()
+    fun2<List<Int?>, Int, Expect<Int?>.() -> Unit>(::get).withNullableSuffix()
 ) {
     companion object : WithAsciiReporter()
 
@@ -24,29 +24,22 @@ class ListFeatureAssertionsSpec : ch.tutteli.atrium.specs.integration.ListFeatur
         var star: Expect<out List<*>> = notImplemented()
 
         a1 get 1
-        a1 = a1 get Index(1) assertIt { }
+        a1 = a1 get index(1) { }
 
         a1b get 1
-        a1b = a1b get Index(1) assertIt { }
+        a1b = a1b get index(1) { }
 
         star get 1
-        star = star get Index(1) assertIt { }
+        star = star get index(1) { }
     }
 }
 
-private val getIndexFun: KFunction2<Expect<List<Int>>, Index, ListGetStep<Int, List<Int>>> = Expect<List<Int>>::get
-private fun getIndexPair() = getIndexFun.name to ::getIndex
+private fun get(expect: Expect<List<Int>>, index: Int, assertionCreator: Expect<Int>.() -> Unit) =
+    expect get index(index) { assertionCreator() }
 
-private fun getIndex(expect: Expect<List<Int>>, index: Int, assertionCreator: Expect<Int>.() -> Unit) =
-    expect get Index(index) assertIt { assertionCreator() }
-
-private val getIndexNullableFun: KFunction2<Expect<List<Int?>>, Index, ListGetStep<Int?, List<Int?>>> =
-    Expect<List<Int?>>::get
-
-private fun getIndexNullablePair() = getIndexNullableFun.name to ::getIndexNullable
-
-private fun getIndexNullable(
+@JvmName("getNullable")
+private fun get(
     expect: Expect<List<Int?>>,
     index: Int,
     assertionCreator: Expect<Int?>.() -> Unit
-) = expect get Index(index) assertIt { assertionCreator() }
+) = expect get index(index) { assertionCreator() }
diff --git a/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/test/kotlin/ch/tutteli/atrium/api/infix/en_GB/MapAssertionsSpec.kt b/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/test/kotlin/ch/tutteli/atrium/api/infix/en_GB/MapAssertionsSpec.kt
index 14ec68fc6..ff1091d90 100644
--- a/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/test/kotlin/ch/tutteli/atrium/api/infix/en_GB/MapAssertionsSpec.kt
+++ b/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/test/kotlin/ch/tutteli/atrium/api/infix/en_GB/MapAssertionsSpec.kt
@@ -3,86 +3,27 @@ package ch.tutteli.atrium.api.infix.en_GB
 import ch.tutteli.atrium.creating.Expect
 import ch.tutteli.atrium.domain.builders.utils.mapArguments
 import ch.tutteli.atrium.specs.*
+import ch.tutteli.atrium.specs.testutils.WithAsciiReporter
+import kotlin.jvm.JvmName
+import kotlin.reflect.KFunction3
+
+private fun <K, V, T> mfun2(
+    f: KFunction3<Expect<Map<out K, V>>, Pair<K, T>, Array<out Pair<K, T>>, Expect<Map<out K, V>>>
+) = fun2(f)
 
 class MapAssertionsSpec : ch.tutteli.atrium.specs.integration.MapAssertionsSpec(
-    fun2(Companion::contains),
-    fun2(Companion::contains).name to Companion::containsNullable,
-    "${fun2(Companion::contains).name} ${KeyValue::class.simpleName}" to Companion::containsKeyWithValueAssertions,
-    "${fun2(Companion::contains).name} ${KeyValue::class.simpleName}" to Companion::containsKeyWithNullableValueAssertions,
-    fun1(Companion::containsKey),
-    fun1(Companion::containsNullableKey),
-    fun1(Companion::containsNotKey),
-    fun1(Companion::containsNotNullableKey),
-    /* string toBe, notToBe to avoid ambiguity error */
-    "toBe ${Empty::class.simpleName}" to Companion::isEmpty,
-    "notToBe ${Empty::class.simpleName}" to Companion::isNotEmpty
+    mfun2<String, Int, Int>(::contains),
+    mfun2<String?, Int?, Int?>(::contains).withNullableSuffix(),
+    mfun2<String, Int, Expect<Int>.() -> Unit>(::contains).adjustName { "$it ${KeyValue::class.simpleName}" },
+    mfun2<String?, Int?, (Expect<Int>.() -> Unit)?>(::contains).adjustName { "$it ${KeyValue::class.simpleName}" }.withNullableSuffix(),
+    fun1<Map<out String, *>, String>(::containsKey),
+    fun1<Map<out String?, *>, String?>(::containsKey).withNullableSuffix(),
+    fun1<Map<out String, *>, String>(::containsNotKey),
+    fun1<Map<out String?, *>, String?>(::containsNotKey).withNullableSuffix(),
+    "toBe ${Empty::class.simpleName}" to ::isEmpty,
+    "notToBe ${Empty::class.simpleName}" to ::isNotEmpty
 ) {
-    companion object {
-        private fun contains(
-            expect: Expect<Map<out String, Int>>,
-            pair: Pair<String, Int>,
-            otherPairs: Array<out Pair<String, Int>>
-        ): Expect<Map<out String, Int>> {
-            return if (otherPairs.isEmpty()) {
-                expect contains (pair.first to pair.second)
-            } else {
-                expect contains Pairs(pair, *otherPairs)
-            }
-        }
-
-        private fun containsNullable(
-            expect: Expect<Map<out String?, Int?>>,
-            pair: Pair<String?, Int?>,
-            otherPairs: Array<out Pair<String?, Int?>>
-        ): Expect<Map<out String?, Int?>> {
-            return if (otherPairs.isEmpty()) {
-                expect contains (pair.first to pair.second)
-            } else {
-                expect contains Pairs(pair, *otherPairs)
-            }
-        }
-
-        private fun containsKeyWithValueAssertions(
-            expect: Expect<Map<out String, Int>>,
-            keyValue: Pair<String, Expect<Int>.() -> Unit>,
-            otherKeyValues: Array<out Pair<String, Expect<Int>.() -> Unit>>
-        ): Expect<Map<out String, Int>> {
-            return if (otherKeyValues.isEmpty()) {
-                expect contains KeyValue(keyValue.first, keyValue.second)
-            } else {
-                mapArguments(keyValue, otherKeyValues).to { KeyValue(it.first, it.second) }.let { (first, others) ->
-                    expect contains All(first, *others)
-                }
-            }
-        }
-
-        private fun containsKeyWithNullableValueAssertions(
-            expect: Expect<Map<out String?, Int?>>,
-            keyValue: Pair<String?, (Expect<Int>.() -> Unit)?>,
-            otherKeyValues: Array<out Pair<String?, (Expect<Int>.() -> Unit)?>>
-        ): Expect<Map<out String?, Int?>> {
-            return if (otherKeyValues.isEmpty()) {
-                expect contains KeyValue(keyValue.first, keyValue.second)
-            } else {
-                mapArguments(keyValue, otherKeyValues).to { KeyValue(it.first, it.second) }.let { (first, others) ->
-                    expect contains All(first, *others)
-                }
-            }
-        }
-
-        private fun containsKey(expect: Expect<Map<out String, *>>, key: String) = expect containsKey key
-
-        private fun containsNullableKey(expect: Expect<Map<out String?, *>>, key: String?) = expect containsKey key
-
-        private fun containsNotKey(expect: Expect<Map<out String, *>>, key: String) = expect containsNotKey key
-
-        private fun containsNotNullableKey(expect: Expect<Map<out String?, *>>, key: String?) =
-            expect containsNotKey key
-
-        private fun isEmpty(expect: Expect<Map<*, *>>) = expect toBe Empty
-
-        private fun isNotEmpty(expect: Expect<Map<*, *>>) = expect notToBe Empty
-    }
+    companion object : WithAsciiReporter()
 
     @Suppress("unused", "UNUSED_VALUE")
     private fun ambiguityTest() {
@@ -249,3 +190,76 @@ class MapAssertionsSpec : ch.tutteli.atrium.specs.integration.MapAssertionsSpec(
 
     }
 }
+
+private fun contains(
+    expect: Expect<Map<out String, Int>>,
+    pair: Pair<String, Int>,
+    otherPairs: Array<out Pair<String, Int>>
+): Expect<Map<out String, Int>> {
+    return if (otherPairs.isEmpty()) {
+        expect contains (pair.first to pair.second)
+    } else {
+        expect contains Pairs(pair, *otherPairs)
+    }
+}
+
+@JvmName("containsNullable")
+private fun contains(
+    expect: Expect<Map<out String?, Int?>>,
+    pair: Pair<String?, Int?>,
+    otherPairs: Array<out Pair<String?, Int?>>
+): Expect<Map<out String?, Int?>> {
+    return if (otherPairs.isEmpty()) {
+        expect contains (pair.first to pair.second)
+    } else {
+        expect contains Pairs(pair, *otherPairs)
+    }
+}
+
+@JvmName("containsKeyWithValueAssertions")
+private fun contains(
+    expect: Expect<Map<out String, Int>>,
+    keyValue: Pair<String, Expect<Int>.() -> Unit>,
+    otherKeyValues: Array<out Pair<String, Expect<Int>.() -> Unit>>
+): Expect<Map<out String, Int>> {
+    return if (otherKeyValues.isEmpty()) {
+        expect contains KeyValue(keyValue.first, keyValue.second)
+    } else {
+        mapArguments(keyValue, otherKeyValues).to { KeyValue(it.first, it.second) }.let { (first, others) ->
+            expect contains All(first, *others)
+        }
+    }
+}
+
+@JvmName("containsKeyWithNullableValueAssertions")
+private fun contains(
+    expect: Expect<Map<out String?, Int?>>,
+    keyValue: Pair<String?, (Expect<Int>.() -> Unit)?>,
+    otherKeyValues: Array<out Pair<String?, (Expect<Int>.() -> Unit)?>>
+): Expect<Map<out String?, Int?>> {
+    return if (otherKeyValues.isEmpty()) {
+        expect contains KeyValue(keyValue.first, keyValue.second)
+    } else {
+        mapArguments(keyValue, otherKeyValues).to { KeyValue(it.first, it.second) }.let { (first, others) ->
+            expect contains All(first, *others)
+        }
+    }
+}
+
+private fun containsKey(expect: Expect<Map<out String, *>>, key: String) =
+    expect containsKey key
+
+@JvmName("containsKeyNullable")
+private fun containsKey(expect: Expect<Map<out String?, *>>, key: String?) =
+    expect containsKey key
+
+private fun containsNotKey(expect: Expect<Map<out String, *>>, key: String) =
+    expect containsNotKey key
+
+@JvmName("containsNotKeyNullable")
+private fun containsNotKey(expect: Expect<Map<out String?, *>>, key: String?) =
+    expect containsNotKey key
+
+private fun isEmpty(expect: Expect<Map<*, *>>) = expect toBe Empty
+
+private fun isNotEmpty(expect: Expect<Map<*, *>>) = expect notToBe Empty
diff --git a/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/test/kotlin/ch/tutteli/atrium/api/infix/en_GB/MapFeatureAssertionsSpec.kt b/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/test/kotlin/ch/tutteli/atrium/api/infix/en_GB/MapFeatureAssertionsSpec.kt
index 20ef9dbf2..4e3532f5b 100644
--- a/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/test/kotlin/ch/tutteli/atrium/api/infix/en_GB/MapFeatureAssertionsSpec.kt
+++ b/apis/infix-en_GB/atrium-api-infix-en_GB-common/src/test/kotlin/ch/tutteli/atrium/api/infix/en_GB/MapFeatureAssertionsSpec.kt
@@ -2,6 +2,8 @@ package ch.tutteli.atrium.api.infix.en_GB
 
 import ch.tutteli.atrium.creating.Expect
 import ch.tutteli.atrium.specs.*
+import ch.tutteli.atrium.specs.testutils.WithAsciiReporter
+import kotlin.jvm.JvmName
 
 class MapFeatureAssertionsSpec : ch.tutteli.atrium.specs.integration.MapFeatureAssertionsSpec(
     property<Map<String, Int>, Set<String>>(Expect<Map<String, Int>>::keys),
@@ -9,23 +11,11 @@ class MapFeatureAssertionsSpec : ch.tutteli.atrium.specs.integration.MapFeatureA
     property<Map<String, Int>, Collection<Int>>(Expect<Map<String, Int>>::values),
     fun1<Map<String, Int>, Expect<Collection<Int>>.() -> Unit>(Expect<Map<String, Int>>::values),
     feature1<Map<String, Int>, String, Int>(Expect<Map<String, Int>>::getExisting),
-    fun2<Map<String, Int>, String, Expect<Int>.() -> Unit>(Companion::getExisting),
+    fun2<Map<String, Int>, String, Expect<Int>.() -> Unit>(::getExisting),
     feature1<Map<String?, Int?>, String?, Int?>(Expect<Map<String?, Int?>>::getExisting).withNullableSuffix(),
-    fun2(Companion::getExisting).name to Companion::getExistingNullable
+    fun2<Map<String?, Int?>, String?, Expect<Int?>.() -> Unit>(::getExisting).withNullableSuffix()
 ) {
-    companion object {
-        private fun getExisting(
-            expect: Expect<Map<String, Int>>,
-            key: String,
-            assertionCreator: Expect<Int>.() -> Unit
-        ): Expect<Map<String, Int>> = expect getExisting Key(key) assertIt { assertionCreator() }
-
-        private fun getExistingNullable(
-            expect: Expect<Map<String?, Int?>>,
-            key: String?,
-            assertionCreator: Expect<Int?>.() -> Unit
-        ): Expect<Map<String?, Int?>> = expect getExisting Key(key) assertIt { assertionCreator() }
-    }
+    companion object : WithAsciiReporter()
 
     @Suppress("unused", "UNUSED_VALUE")
     private fun ambiguityTest() {
@@ -40,9 +30,22 @@ class MapFeatureAssertionsSpec : ch.tutteli.atrium.specs.integration.MapFeatureA
         a3 getExisting null as String?
         star getExisting "a"
 
-        a1 = a1 getExisting Key("a") assertIt { }
-        a2 = a2 getExisting Key(1) assertIt { }
-        a3 = a3 getExisting Key(null) assertIt { }
-        star = star getExisting Key("a") assertIt { }
+        a1 = a1 getExisting key("a") { }
+        a2 = a2 getExisting key(1) { }
+        a3 = a3 getExisting key(null) { }
+        star = star getExisting key("a") { }
     }
 }
+
+private fun getExisting(
+    expect: Expect<Map<String, Int>>,
+    key: String,
+    assertionCreator: Expect<Int>.() -> Unit
+): Expect<Map<String, Int>> = expect getExisting key(key) { assertionCreator() }
+
+@JvmName("getExistingNullable")
+private fun getExisting(
+    expect: Expect<Map<String?, Int?>>,
+    key: String?,
+    assertionCreator: Expect<Int?>.() -> Unit
+): Expect<Map<String?, Int?>> = expect getExisting key(key) { assertionCreator() }
diff --git a/domain/builders/atrium-domain-builders-common/src/main/kotlin/ch/tutteli/atrium/domain/builders/creating/NewFeatureAssertionsBuilder.kt b/domain/builders/atrium-domain-builders-common/src/main/kotlin/ch/tutteli/atrium/domain/builders/creating/NewFeatureAssertionsBuilder.kt
index 4cf5ddc9c..0ecd76652 100644
--- a/domain/builders/atrium-domain-builders-common/src/main/kotlin/ch/tutteli/atrium/domain/builders/creating/NewFeatureAssertionsBuilder.kt
+++ b/domain/builders/atrium-domain-builders-common/src/main/kotlin/ch/tutteli/atrium/domain/builders/creating/NewFeatureAssertionsBuilder.kt
@@ -80,23 +80,16 @@ object NewFeatureAssertionsBuilder : NewFeatureAssertions {
         description: Translatable,
         provider: T.() -> R
     ): ExtractedFeaturePostStep<T, R> =
-        genericFeature(expect, createMetaFeature(expect, description, provider))
+        genericFeature(expect, ExpectImpl.feature.meta.create(expect, description, provider))
 
     fun <T, R> genericSubjectBasedFeature(
         expect: Expect<T>,
         provider: (T) -> MetaFeature<R>
     ): ExtractedFeaturePostStep<T, R> = ExpectImpl.feature.genericFeature(
         expect,
-        expect.maybeSubject.fold(this::createFeatureSubjectNotDefined) { provider(it) }
+        ExpectImpl.feature.meta.createSubjectBased(expect, provider)
     )
 
-    private fun <R> createFeatureSubjectNotDefined(): MetaFeature<R> =
-        MetaFeature(
-            ErrorMessages.DEDSCRIPTION_BASED_ON_SUBJECT,
-            RawString.create(ErrorMessages.REPRESENTATION_BASED_ON_SUBJECT_NOT_DEFINED),
-            None
-        )
-
     override inline fun <T, R> genericFeature(
         expect: Expect<T>,
         metaFeature: MetaFeature<R>
@@ -107,30 +100,7 @@ object NewFeatureAssertionsBuilder : NewFeatureAssertions {
         description: String,
         provider: (T) -> R
     ): ExtractedFeaturePostStep<T, R> =
-        genericFeature(expect, createMetaFeature(expect, description, provider))
-
-    private fun <T, R> createMetaFeature(
-        expect: Expect<T>,
-        description: String,
-        provider: (T) -> R
-    ): MetaFeature<R> = createMetaFeature(expect, Untranslatable(description), provider)
-
-    private fun <T, R> createMetaFeature(
-        expect: Expect<T>,
-        description: Translatable,
-        provider: (T) -> R
-    ): MetaFeature<R> {
-        return expect.maybeSubject.fold({
-            MetaFeature(
-                description,
-                RawString.create(ErrorMessages.REPRESENTATION_BASED_ON_SUBJECT_NOT_DEFINED),
-                None
-            )
-        }) {
-            val prop = provider(it)
-            MetaFeature(description, prop, Some(prop))
-        }
-    }
+        genericFeature(expect, ExpectImpl.feature.meta.create(expect, description, provider))
 
     /**
      * Returns [MetaFeatureBuilder] which helps to create a [MetaFeature].
@@ -143,6 +113,7 @@ object NewFeatureAssertionsBuilder : NewFeatureAssertions {
  * into an overload ambiguity, then either [p] (for property) or one of the `fN` functions (e.g. [f2] for
  * a function which expects 2 arguments).
  */
+//TODO move to API, this could potentially be different per API
 class MetaFeatureOption<T>(private val expect: Expect<T>) {
 
     /**
@@ -338,4 +309,43 @@ object MetaFeatureBuilder {
     fun <A1, A2, A3, A4, A5, R> f5(expect: Expect<*>, f: KFunction5<A1, A2, A3, A4, A5, R>, a1: A1, a2: A2, a3: A3, a4: A4, a5: A5) =
         MetaFeature(coreFactory.newMethodCallFormatter().formatCall(f.name, arrayOf(a1, a2, a3, a4, a5)), f.invoke(a1, a2, a3, a4, a5))
     //@formatter:on
+
+    /**
+     * creates a [MetaFeature] which is entirely based on the subject (i.e. also the description).
+     */
+    fun <T, R> createSubjectBased(
+        expect: Expect<T>,
+        provider: (T) -> MetaFeature<R>
+    ): MetaFeature<R> = expect.maybeSubject.fold(this::createFeatureSubjectNotDefined) { provider(it) }
+
+    private fun <R> createFeatureSubjectNotDefined(): MetaFeature<R> =
+        MetaFeature(
+            ErrorMessages.DEDSCRIPTION_BASED_ON_SUBJECT,
+            RawString.create(ErrorMessages.REPRESENTATION_BASED_ON_SUBJECT_NOT_DEFINED),
+            None
+        )
+
+    fun <T, R> create(
+        expect: Expect<T>,
+        description: String,
+        provider: (T) -> R
+    ): MetaFeature<R> = create(expect, Untranslatable(description), provider)
+
+    fun <T, R> create(
+        expect: Expect<T>,
+        description: Translatable,
+        provider: (T) -> R
+    ): MetaFeature<R> {
+        return expect.maybeSubject.fold({
+            MetaFeature(
+                description,
+                RawString.create(ErrorMessages.REPRESENTATION_BASED_ON_SUBJECT_NOT_DEFINED),
+                None
+            )
+        }) {
+            val feature = provider(it)
+            MetaFeature(description, feature, Some(feature))
+        }
+    }
+
 }
diff --git a/domain/builders/atrium-domain-builders-common/src/main/kotlin/ch/tutteli/atrium/domain/builders/creating/changers/impl/featureextractor/defaultImpls.kt b/domain/builders/atrium-domain-builders-common/src/main/kotlin/ch/tutteli/atrium/domain/builders/creating/changers/impl/featureextractor/defaultImpls.kt
index 67f000595..c45509e06 100644
--- a/domain/builders/atrium-domain-builders-common/src/main/kotlin/ch/tutteli/atrium/domain/builders/creating/changers/impl/featureextractor/defaultImpls.kt
+++ b/domain/builders/atrium-domain-builders-common/src/main/kotlin/ch/tutteli/atrium/domain/builders/creating/changers/impl/featureextractor/defaultImpls.kt
@@ -4,6 +4,7 @@ import ch.tutteli.atrium.core.None
 import ch.tutteli.atrium.core.Option
 import ch.tutteli.atrium.core.Some
 import ch.tutteli.atrium.creating.Expect
+import ch.tutteli.atrium.creating.FeatureExpect
 import ch.tutteli.atrium.domain.builders.creating.changers.FeatureExtractorBuilder
 import ch.tutteli.atrium.domain.builders.creating.changers.FeatureOptions
 import ch.tutteli.atrium.domain.creating.changers.ExtractedFeaturePostStep
@@ -68,13 +69,13 @@ class FinalStepImpl<T, R>(
             extractAndApply = { assertionCreator -> extractIt(this, Some(assertionCreator)) }
         )
 
-    private fun extractIt(expect: Expect<T>, subAssertions: Option<Expect<R>.() -> Unit>) =
+    private fun extractIt(expect: Expect<T>, maybeSubAssertions: Option<Expect<R>.() -> Unit>): FeatureExpect<T, R> =
         featureExtractor.extract(
             expect,
             featureOptions?.description ?: featureExtractionStep.description,
             featureExtractionStep.representationForFailure,
             featureExtraction,
-            subAssertions,
+            maybeSubAssertions,
             featureOptions?.representationInsteadOfFeature
         )
 }
diff --git a/domain/builders/atrium-domain-builders-common/src/main/kotlin/ch/tutteli/atrium/domain/builders/utils/VarArgHelper.kt b/domain/builders/atrium-domain-builders-common/src/main/kotlin/ch/tutteli/atrium/domain/builders/utils/VarArgHelper.kt
index a73e9c06c..34f69587c 100644
--- a/domain/builders/atrium-domain-builders-common/src/main/kotlin/ch/tutteli/atrium/domain/builders/utils/VarArgHelper.kt
+++ b/domain/builders/atrium-domain-builders-common/src/main/kotlin/ch/tutteli/atrium/domain/builders/utils/VarArgHelper.kt
@@ -19,7 +19,7 @@ interface VarArgHelper<out T> {
     /**
      * Creates an [ArgumentMapperBuilder] which allows to map [expected] and [otherExpected].
      */
-    val mapArguments get() = ArgumentMapperBuilder(expected, otherExpected)
+    val mapArguments: ArgumentMapperBuilder<T> get() = ArgumentMapperBuilder(expected, otherExpected)
 
     /**
      * Returns the arguments as [List].