[Gradle][KT-53342] Implement simple SingleTargetAndroidSourceSetLayoutTest

libraries/tools/kotlin-gradle-plugin/src/functionalTest/kotlin/org/jetbrains/kotlin/gradle/sources/android/SingleTargetAndroidSourceSetLayoutTest.kt

@@ -0,0 +1,73 @@
+/*
+ * Copyright 2010-2022 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+@file:Suppress("FunctionName")
+
+package org.jetbrains.kotlin.gradle.sources.android
+
+import com.android.build.gradle.BaseExtension
+import com.android.build.gradle.LibraryPlugin
+import org.gradle.api.internal.project.ProjectInternal
+import org.gradle.testfixtures.ProjectBuilder
+import org.jetbrains.kotlin.gradle.addBuildEventsListenerRegistryMock
+import org.jetbrains.kotlin.gradle.plugin.KotlinAndroidPluginWrapper
+import org.jetbrains.kotlin.gradle.plugin.KotlinSourceSet
+import org.jetbrains.kotlin.gradle.utils.androidExtension
+import org.junit.Test
+import kotlin.test.BeforeTest
+import kotlin.test.assertEquals
+import kotlin.test.assertSame
+
+class SingleTargetAndroidSourceSetLayoutTest {
+    private val project = ProjectBuilder.builder().build() as ProjectInternal
+
+    private val android: BaseExtension = run {
+        addBuildEventsListenerRegistryMock(project)
+        project.plugins.apply(LibraryPlugin::class.java)
+        project.androidExtension
+    }
+
+    @BeforeTest
+    fun setup() {
+        project.plugins.apply(KotlinAndroidPluginWrapper::class.java)
+        android.compileSdkVersion(31)
+    }
+
+    @Test
+    fun `test - default configuration - AndroidSourceSet has associated KotlinSourceSet`() {
+        android.sourceSets.all { androidSourceSet -> project.assertSingleKotlinSourceSet(androidSourceSet) }
+        project.evaluate()
+    }
+
+    @Test
+    @Suppress("deprecation")
+    fun `test - default configuration - AndroidSourceSet has KotlinSourceSet as convention`() {
+        android.sourceSets.all { androidSourceSet ->
+            assertSame(
+                project.assertSingleKotlinSourceSet(androidSourceSet),
+                (androidSourceSet as org.gradle.api.internal.HasConvention).convention.plugins["kotlin"] as? KotlinSourceSet,
+                "Expected Convention 'kotlin' on AndroidSourceSet: ${androidSourceSet.name}"
+            )
+        }
+        project.evaluate()
+    }
+
+
+    @Test
+    fun `test - with flavors - AndroidSourceSet has associated KotlinSourceSet`() {
+        android.flavorDimensions("price", "market")
+        android.productFlavors {
+            it.create("free").dimension = "price"
+            it.create("paid").dimension = "price"
+            it.create("german").dimension = "market"
+            it.create("usa").dimension = "market"
+        }
+
+        android.sourceSets.all { androidSourceSet ->
+            val kotlinSourceSet = project.assertSingleKotlinSourceSet(androidSourceSet)
+            assertEquals(androidSourceSet.name, kotlinSourceSet.name)
+        }
+    }
+}

libraries/tools/kotlin-gradle-plugin/src/functionalTest/kotlin/org/jetbrains/kotlin/gradle/sources/android/assertSingleKotlinSourceSet.kt

@@ -0,0 +1,33 @@
+/*
+ * Copyright 2010-2022 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+@file:Suppress("DEPRECATION")
+
+package org.jetbrains.kotlin.gradle.sources.android
+
+import com.android.build.gradle.api.AndroidSourceSet
+import org.gradle.api.Project
+import org.jetbrains.kotlin.gradle.dsl.kotlinExtension
+import org.jetbrains.kotlin.gradle.plugin.KotlinSourceSet
+import org.jetbrains.kotlin.gradle.plugin.sources.android.androidSourceSetInfoOrNull
+import kotlin.test.fail
+
+fun Project.assertSingleKotlinSourceSet(androidSourceSet: AndroidSourceSet): KotlinSourceSet {
+    val kotlinSourceSets = kotlinExtension.sourceSets
+        .filter { kotlinSourceSet -> kotlinSourceSet.androidSourceSetInfoOrNull?.androidSourceSetName == androidSourceSet.name }
+
+    if (kotlinSourceSets.isEmpty()) {
+        fail("Missing KotlinSourceSet for AndroidSourceSet: ${androidSourceSet.name}")
+    }
+
+    if (kotlinSourceSets.size > 1) {
+        fail(
+            "More than one KotlinSourceSet associated with AndroidSourceSet: ${androidSourceSet.name}. " +
+                    "KotlinSourceSets: ${kotlinSourceSets.map { it.name }}"
+        )
+    }
+
+    return kotlinSourceSets.single()
+}