[Gradle] Add integration test for associated 'functionalTest' style sources

Experiments with the DefaultKotlinCompilationAssociator where made
during KT-60937. One experiment broke running functionalTests in
kotlin.git in bootstrap mode. This case was not yet covered by
CI.

^KT-60937 Verification Pending

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/TestFixturesIT.kt

@@ -94,6 +94,35 @@ class TestFixturesIT : KGPBaseTest() {
         }
     }
 
+    @DisplayName("Test associated 'functionalTest' compilation can compile and run with test and testFixtures in JVM project")
+    @MppGradlePluginTests
+    @GradleTest
+    fun testTestFixturesAndFunctionalTestsInJvmProject(gradleVersion: GradleVersion) {
+        project("jvm-test-fixtures-functionalTest", gradleVersion) {
+            build("functionalTest") {
+                assertOutputContains("src/main OK!")
+                assertOutputContains("src/test OK!")
+                assertOutputContains("src/testFixtures OK!")
+                assertOutputContains("src/functionalTest OK!")
+            }
+        }
+    }
+
+    @DisplayName("Test associated 'functionalTest' compilation can compile and run with test and testFixtures in Multiplatform project")
+    @MppGradlePluginTests
+    @GradleTest
+    fun testTestFixturesAndFunctionalTestsInMppProject(gradleVersion: GradleVersion) {
+        project("mpp-test-fixtures-functionalTest", gradleVersion) {
+            build("functionalTest") {
+                assertOutputContains("src/main OK!")
+                assertOutputContains("src/test OK!")
+                assertOutputContains("src/testFixtures OK!")
+                assertOutputContains("src/functionalTest OK!")
+            }
+        }
+    }
+
+
     companion object {
         private const val JVM_TEST_FIXTURES_PROJECT_NAME = "jvm-test-fixtures"
         private const val MPP_TEST_FIXTURES_PROJECT_NAME = "mpp-test-fixtures"

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/jvm-test-fixtures-functionalTest/build.gradle.kts

@@ -0,0 +1,32 @@
+@file:Suppress("HasPlatformType")
+
+plugins {
+    kotlin("jvm")
+    `java-test-fixtures`
+}
+
+repositories {
+    mavenLocal()
+    mavenCentral()
+}
+
+/* Create functionalTest (java) source set */
+val functionalTestSourceSet = sourceSets.create("functionalTest")
+val functionalTestCompilation = kotlin.target.compilations.getByName("functionalTest")
+
+/* Associate 'functionalTest' with 'test' */
+functionalTestCompilation.associateWith(kotlin.target.compilations.getByName("test"))
+
+/* Create test task */
+val functionalTest = tasks.register<Test>("functionalTest") {
+    testClassesDirs = functionalTestSourceSet.output.classesDirs
+    classpath = functionalTestSourceSet.runtimeClasspath
+    testLogging {
+        events("passed", "skipped", "failed")
+        showStandardStreams = true
+    }
+}
+
+dependencies {
+    testImplementation(kotlin("test-junit"))
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/jvm-test-fixtures-functionalTest/src/functionalTest/java/FunctionalTestJava.java

@@ -0,0 +1,2 @@
+public class FunctionalTestJava {
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/jvm-test-fixtures-functionalTest/src/functionalTest/kotlin/Executable.kt

@@ -0,0 +1,25 @@
+import kotlin.test.Test
+
+class Executable {
+    @Test
+    fun runTest() {
+        MainJava()
+        MainKotlin()
+        MainKotlinInternal()
+        println("src/main OK!")
+
+        TestJava()
+        TestKotlin()
+        TestKotlinInternal()
+        println("src/test OK!")
+
+        TestFixturesJava()
+        TestFixturesKotlin()
+        TestFixturesKotlinInternal()
+        println("src/testFixtures OK!")
+
+        FunctionalTestKotlin()
+        FunctionalTestJava()
+        println("src/functionalTest OK!")
+    }
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/jvm-test-fixtures-functionalTest/src/functionalTest/kotlin/FunctionalTestKotlin.kt

@@ -0,0 +1,2 @@
+internal class FunctionalTestKotlin {
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/jvm-test-fixtures-functionalTest/src/main/java/MainJava.java

@@ -0,0 +1,2 @@
+public class MainJava {
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/jvm-test-fixtures-functionalTest/src/main/kotlin/MainKotlin.kt

@@ -0,0 +1,2 @@
+class MainKotlin
+internal class MainKotlinInternal

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/jvm-test-fixtures-functionalTest/src/test/java/TestJava.java

@@ -0,0 +1,9 @@
+public class TestJava {
+    public TestJava() {
+        new MainJava();
+        new MainKotlin();
+
+        new TestFixturesJava();
+        new TestFixturesKotlin();
+    }
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/jvm-test-fixtures-functionalTest/src/test/kotlin/TestKotlin.kt

@@ -0,0 +1,2 @@
+class TestKotlin
+internal class TestKotlinInternal

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/jvm-test-fixtures-functionalTest/src/testFixtures/java/TestFixturesJava.java

@@ -0,0 +1,6 @@
+public class TestFixturesJava {
+    public TestFixturesJava() {
+        new MainJava();
+        new MainKotlin();
+    }
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/jvm-test-fixtures-functionalTest/src/testFixtures/kotlin/TestFixturesKotlin.kt

@@ -0,0 +1,2 @@
+class TestFixturesKotlin
+internal class TestFixturesKotlinInternal

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/mpp-test-fixtures-functionalTest/build.gradle.kts

@@ -0,0 +1,36 @@
+plugins {
+    kotlin("multiplatform")
+    java
+    `java-test-fixtures`
+}
+
+repositories {
+    mavenLocal()
+    mavenCentral()
+}
+
+kotlin {
+    jvm { withJava() }
+    val testCompilation = jvm().compilations.getByName("test")
+    testCompilation.associateWith(jvm().compilations.getByName("testFixtures"))
+
+    val functionalTestCompilation = jvm().compilations.create("functionalTest")
+    functionalTestCompilation.associateWith(testCompilation)
+
+    sourceSets.getByName("jvmTest").dependencies {
+        implementation(kotlin("test-junit"))
+    }
+}
+
+/* Create test task */
+val functionalTest = tasks.register<Test>("functionalTest") {
+    val compilation = kotlin.jvm().compilations.getByName("functionalTest")
+    testClassesDirs = compilation.output.classesDirs
+    classpath = compilation.output.classesDirs +
+            project.files({ kotlin.jvm().compilations.getByName("functionalTest").runtimeDependencyFiles })
+
+    testLogging {
+        events("passed", "skipped", "failed")
+        showStandardStreams = true
+    }
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/mpp-test-fixtures-functionalTest/src/jvmFunctionalTest/java/FunctionalTestJava.java

@@ -0,0 +1,2 @@
+public class FunctionalTestJava {
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/mpp-test-fixtures-functionalTest/src/jvmFunctionalTest/kotlin/Executable.kt

@@ -0,0 +1,25 @@
+import kotlin.test.Test
+
+class Executable {
+    @Test
+    fun runTest() {
+        MainJava()
+        MainKotlin()
+        MainKotlinInternal()
+        println("src/main OK!")
+
+        TestJava()
+        TestKotlin()
+        TestKotlinInternal()
+        println("src/test OK!")
+
+        TestFixturesJava()
+        TestFixturesKotlin()
+        TestFixturesKotlinInternal()
+        println("src/testFixtures OK!")
+
+        FunctionalTestKotlin()
+        FunctionalTestJava()
+        println("src/functionalTest OK!")
+    }
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/mpp-test-fixtures-functionalTest/src/jvmFunctionalTest/kotlin/FunctionalTestKotlin.kt

@@ -0,0 +1,2 @@
+internal class FunctionalTestKotlin {
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/mpp-test-fixtures-functionalTest/src/jvmMain/java/MainJava.java

@@ -0,0 +1,2 @@
+public class MainJava {
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/mpp-test-fixtures-functionalTest/src/jvmMain/kotlin/MainKotlin.kt

@@ -0,0 +1,2 @@
+class MainKotlin
+internal class MainKotlinInternal

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/mpp-test-fixtures-functionalTest/src/jvmTest/java/TestJava.java

@@ -0,0 +1,9 @@
+public class TestJava {
+    public TestJava() {
+        new MainJava();
+        new MainKotlin();
+
+        new TestFixturesJava();
+        new TestFixturesKotlin();
+    }
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/mpp-test-fixtures-functionalTest/src/jvmTest/kotlin/TestKotlin.kt

@@ -0,0 +1,2 @@
+class TestKotlin
+internal class TestKotlinInternal

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/mpp-test-fixtures-functionalTest/src/jvmTestFixtures/java/TestFixturesJava.java

@@ -0,0 +1,6 @@
+public class TestFixturesJava {
+    public TestFixturesJava() {
+        new MainJava();
+        new MainKotlin();
+    }
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/mpp-test-fixtures-functionalTest/src/jvmTestFixtures/kotlin/TestFixturesKotlin.kt

@@ -0,0 +1,2 @@
+class TestFixturesKotlin
+internal class TestFixturesKotlinInternal