Introduce execution & test run API, KT-32679

* KotlinExecution
* KotlinExecutionSource
* KotlinTestRun
* Aggregating executions and execution sources
* KotlinTargetWithTests

* Add a `testableTargets` extension
* Make some Kotlin/Native targets testable (this requires
  having a separate preset type for them)
* Implement test runs encapsulating the tests for all
  existing testable targets by refactoring their
  TargetConfigurator classes

Issue #KT-32679 Fixed

libraries/tools/kotlin-gradle-plugin-api/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/KotlinExecution.kt

@@ -0,0 +1,56 @@
+/*
+ * Copyright 2010-2019 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.
+ */
+
+package org.jetbrains.kotlin.gradle.plugin
+
+import org.gradle.api.Named
+import org.gradle.api.Task
+import org.gradle.api.tasks.TaskProvider
+import org.jetbrains.kotlin.gradle.plugin.KotlinExecution.ExecutionSource
+
+/**
+ * An execution of Kotlin code. Executions in a single family (e.g. test runs) are distinguished by [Named.getName].
+ * Names may not be unique across different execution families, such as test runs of different targets.
+ *
+ * A particular kind of execution is a [KotlinTestRun] which runs tests.
+ */
+interface KotlinExecution<out SourceType : ExecutionSource> : Named {
+    interface ExecutionSource
+
+    /**
+     * The source of the executable code that this execution runs from. It is usually set via members of  execution source support
+     * interfaces, such as [CompilationExecutionSourceSupport] or [ClasspathTestRunSourceSupport], or `setExecutionSourceFrom*` functions.
+     */
+    val executionSource: SourceType
+}
+
+interface KotlinTargetExecution<out SourceType : ExecutionSource> : KotlinExecution<SourceType> {
+    val target: KotlinTarget
+}
+
+/**
+ * An execution source that is produced by a [compilation].
+ *
+ * See also: [CompilationExecutionSourceSupport].
+ */
+interface CompilationExecutionSource<CompilationType : KotlinCompilation<*>> : ExecutionSource {
+    val compilation: CompilationType
+}
+
+interface CompilationExecutionSourceSupport<in T : KotlinCompilationToRunnableFiles<*>> {
+    /**
+     * Select a compilation to run the execution from.
+     *
+     * The [compilation]'s [KotlinCompilationToRunnableFiles.runtimeDependencyFiles]
+     * will be treated as runtime dependencies, and its [output] as runnable files.
+     *
+     * This overrides other [KotlinExecution.executionSource] selection options.
+     */
+    fun setExecutionSourceFrom(compilation: T)
+}
+
+interface ExecutionTaskHolder<T : Task> {
+    val executionTask: TaskProvider<T>
+}

libraries/tools/kotlin-gradle-plugin-api/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/KotlinTarget.kt

@@ -54,4 +54,14 @@ interface KotlinTarget : Named, HasAttributes {
     val preset: KotlinTargetPreset<out KotlinTarget>?
 
     override fun getName(): String = targetName
+}
+
+interface KotlinTargetWithTests<E : KotlinExecution.ExecutionSource, T : KotlinTargetTestRun<E>> : KotlinTarget {
+    /** The container with the test run executions.
+     * A target may automatically create and configure a test run by the name [DEFAULT_TEST_RUN_NAME]. */
+    val testRuns: NamedDomainObjectContainer<T>
+
+    companion object {
+        const val DEFAULT_TEST_RUN_NAME = "test"
+    }
 }

libraries/tools/kotlin-gradle-plugin-api/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/KotlinTestRun.kt

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2010-2019 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.
+ */
+
+package org.jetbrains.kotlin.gradle.plugin
+
+import groovy.lang.Closure
+import org.gradle.api.file.FileCollection
+import org.gradle.api.tasks.testing.TestFilter
+import org.gradle.util.ConfigureUtil
+
+interface KotlinTestRun<out SourceType : KotlinExecution.ExecutionSource> : KotlinExecution<SourceType> {
+    fun filter(configureFilter: TestFilter.() -> Unit)
+
+    fun filter(configureFilter: Closure<*>) = filter { ConfigureUtil.configureSelf(configureFilter, this) }
+}
+
+interface KotlinTargetTestRun<ExecutionSource : KotlinExecution.ExecutionSource> :
+    KotlinTestRun<ExecutionSource>,
+    KotlinTargetExecution<ExecutionSource>
+
+interface JvmClasspathTestRunSource : KotlinExecution.ExecutionSource {
+    val testClassesDirs: FileCollection
+    val classpath: FileCollection
+}
+
+interface ClasspathTestRunSourceSupport {
+    /**
+     * Select the exact [classpath] to run the tests from.
+     *
+     * Only the classes from [testClasses] will be treated as tests.
+     *
+     * This overrides other [KotlinExecution.executionSource] selection options.
+     */
+    fun setExecutionSourceFrom(classpath: FileCollection, testClassesDirs: FileCollection)
+}