Introduce functional tests (#26)

* Introduce functional unit tests akin to the JUnit 5 Java plugin

This adds "FunctionalSpec" classes that verify the correct execution
of JUnit 5 tests in different scenarios. We've had some issues with
test discovery in the past, which go beyond the "pure" plugin tests
that assert the correct configuration and behavior. These new tests
create virtual projects & run their unit tests with GradleRunner,
then assert if everything went as expected.

These tests are detecting the incorrect behavior for issues like #25,
which are related to a bug in the Kotlin copy task, for instance.

* #25: Fix destination of copied Kotlin classes for AGP3

Author: mannodermaus

android-junit5/build.gradle

@@ -64,22 +64,6 @@ processTestResources {
   }
 }
 
-// https://docs.gradle.org/current/userguide/test_kit.html#sub:test-kit-classpath-injection
-// Write the plugin's classpath to a file to share with the tests
-task createTestClasspathManifest {
-  def outputDir = file("$buildDir/resources/test")
-
-  inputs.files sourceSets.main.runtimeClasspath
-  outputs.dir outputDir
-
-  doLast {
-    outputDir.mkdirs()
-    file("$outputDir/plugin-classpath.txt").text = sourceSets.main.runtimeClasspath.join("\n")
-  }
-}
-
-processTestResources.finalizedBy createTestClasspathManifest
-
 // ------------------------------------------------------------------------------------------------
 // Test Setup
 //
@@ -96,11 +80,27 @@ final def jacocoData3x = "$buildDir/jacoco/testAgp3x.exec"
 
 configurations {
   testAgp2xCompile {
+    description = "Dependencies used for compiling tests using Android Gradle Plugin 2.x"
     extendsFrom configurations.testCompile
   }
   testAgp3xCompile {
+    description = "Dependencies used for compiling tests using Android Gradle Plugin 3.x"
     extendsFrom configurations.testCompile
   }
+  functionalTest {
+    description = "Local dependencies used for compiling & running tests source code " +
+        "inside of Gradle functional tests"
+  }
+  functionalTestAgp2x {
+    description = "Local dependencies used for compiling & running tests source code " +
+        "inside of Gradle functional tests with Android Gradle Plugin 2.x"
+    extendsFrom configurations.functionalTest
+  }
+  functionalTestAgp3x {
+    description = "Local dependencies used for compiling & running tests source code " +
+        "inside of Gradle functional tests with Android Gradle Plugin 3.x"
+    extendsFrom configurations.functionalTest
+  }
 }
 
 sourceSets {
@@ -148,6 +148,37 @@ task testAgp3x(type: Test) {
 // Combine all tests when executing the main JUnit task
 tasks.getByName("test").dependsOn(testAgp2x, testAgp3x)
 
+// https://docs.gradle.org/current/userguide/test_kit.html#sub:test-kit-classpath-injection
+// Write the plugin's classpath to a file to share with the tests
+task createTestClasspathManifests {
+  description =
+      "Generate classpath manifests for functional tests so that they can reference locally" +
+          " built libraries for use with Gradle Test Kit"
+  def outputDir = file("$buildDir/resources/test")
+
+  inputs.files sourceSets.main.runtimeClasspath
+  inputs.files sourceSets.testAgp2x.runtimeClasspath
+  inputs.files sourceSets.testAgp3x.runtimeClasspath
+  inputs.files configurations.testAgp2xCompile
+  inputs.files configurations.testAgp3xCompile
+  outputs.dir outputDir
+
+  doLast {
+    outputDir.mkdirs()
+    file("$outputDir/plugin-classpath.txt").text = sourceSets.main.runtimeClasspath.join("\n")
+    file("$outputDir/plugin-2x-classpath.txt").text =
+        sourceSets.testAgp2x.runtimeClasspath.join("\n")
+    file("$outputDir/plugin-3x-classpath.txt").text =
+        sourceSets.testAgp3x.runtimeClasspath.join("\n")
+    file("$outputDir/functional-test-compile-2x-classpath.txt").text =
+        configurations.functionalTestAgp2x.files.join("\n")
+    file("$outputDir/functional-test-compile-3x-classpath.txt").text =
+        configurations.functionalTestAgp3x.files.join("\n")
+  }
+}
+
+processTestResources.finalizedBy createTestClasspathManifests
+
 // ------------------------------------------------------------------------------------------------
 // Dependency Definitions
 // ------------------------------------------------------------------------------------------------
@@ -159,11 +190,19 @@ dependencies {
   compileOnly "com.android.tools.build:gradle:$ANDROID_PLUGIN_2X_VERSION"
 
   testCompile "junit:junit:$JUNIT4_VERSION"
+  testCompile "commons-lang:commons-lang:2.6"
   testCompile "org.spockframework:spock-core:$SPOCK_VERSION"
   testCompile "org.jetbrains.kotlin:kotlin-gradle-plugin:$KOTLIN_VERSION"
   testCompileOnly "com.android.tools.build:gradle:$ANDROID_PLUGIN_3X_VERSION"
   testAgp2xCompile "com.android.tools.build:gradle:$ANDROID_PLUGIN_2X_VERSION"
   testAgp3xCompile "com.android.tools.build:gradle:$ANDROID_PLUGIN_3X_VERSION"
+
+  functionalTest "junit:junit:$JUNIT4_VERSION"
+  functionalTest "org.junit.jupiter:junit-jupiter-api:$JUNIT_JUPITER_VERSION"
+  functionalTest "org.junit.jupiter:junit-jupiter-engine:$JUNIT_JUPITER_VERSION"
+  functionalTest "org.junit.platform:junit-platform-console:$JUNIT_PLATFORM_VERSION"
+  functionalTestAgp2x "com.android.tools.build:gradle:$ANDROID_PLUGIN_2X_VERSION"
+  functionalTestAgp3x "com.android.tools.build:gradle:$ANDROID_PLUGIN_3X_VERSION"
 }
 
 // ------------------------------------------------------------------------------------------------

android-junit5/src/main/groovy/de/mannodermaus/gradle/plugins/android_junit5/kotlin/AndroidJUnit5CopyKotlin.groovy

@@ -45,7 +45,7 @@ class AndroidJUnit5CopyKotlin extends Copy {
     @Override
     void execute(AndroidJUnit5CopyKotlin copyTask) {
       copyTask.from "$project.buildDir/tmp/kotlin-classes/${variant.name}UnitTest"
-      copyTask.into "$project.buildDir/intermediates/classes/test/$variant.name"
+      copyTask.into "$project.buildDir/intermediates/classes/test/$variant.flavorName/$variant.buildType.name"
       copyTask.group = TASK_GROUP
 
       testTask.dependsOn copyTask