Update behavior for custom RunnerBuilder args & adjust tests to new behavior

Author: mannodermaus

android-junit5-tests/src/test/groovy/de/mannodermaus/gradle/plugins/junit5/PluginSpec.groovy

@@ -866,26 +866,6 @@ class PluginSpec extends Specification {
     project.tasks.findByName("jacocoTestReportRelease") == null
   }
 
-  def "Instrumentation Test Integration: Doesn't attach RunnerBuilder if disabled"() {
-    when:
-    Project project = factory.newProject(rootProject())
-        .asAndroidApplication()
-        .applyJunit5Plugin()
-        .build()
-
-    project.android {
-      testOptions.junitPlatform.instrumentationTests {
-        enabled false
-      }
-    }
-
-    project.evaluate()
-
-    then:
-    def args = project.android.defaultConfig.getTestInstrumentationRunnerArguments()
-    assert !args.containsKey("runnerBuilder")
-  }
-
   def "Instrumentation Test Integration: Attaches RunnerBuilder"() {
     when:
     Project project = factory.newProject(rootProject())
@@ -907,7 +887,7 @@ class PluginSpec extends Specification {
     assert args["runnerBuilder"].contains("AndroidJUnit5Builder")
   }
 
-  def "Instrumentation Test Integration: Appends RunnerBuilder if another is already present"() {
+  def "Instrumentation Test Integration: Raise error if another RunnerBuilder replaces ours"() {
     when:
     Project project = factory.newProject(rootProject())
         .asAndroidApplication()
@@ -927,37 +907,37 @@ class PluginSpec extends Specification {
     project.evaluate()
 
     then:
-    def args = project.android.defaultConfig.getTestInstrumentationRunnerArguments()
-    assert args.containsKey("runnerBuilder")
-
-    // Intentional comma
-    assert args["runnerBuilder"].contains("com.something.else.OtherRunnerBuilder,")
-    assert args["runnerBuilder"].contains("AndroidJUnit5Builder")
+    def expect = thrown(ProjectConfigurationException)
+    assert expect.cause.message == "Custom runnerBuilder is overwriting JUnit 5 integration! Change your declaration to 'com.something.else.OtherRunnerBuilder,de.mannodermaus.junit5.AndroidJUnit5Builder'."
   }
 
-  def "Instrumentation Test Integration: Runner Library is not added automatically if disabled"() {
+  def "Instrumentation Test Integration: Don't raise error if another RunnerBuilder acknowledges ours"() {
     when:
     Project project = factory.newProject(rootProject())
         .asAndroidApplication()
+        .applyJunit5Plugin()
         .build()
 
     project.android {
-      testOptions.junitPlatform {
-        instrumentationTests {
-          enabled false
-        }
+      defaultConfig {
+        testInstrumentationRunnerArgument "runnerBuilder", "com.something.else.OtherRunnerBuilder,de.mannodermaus.junit5.AndroidJUnit5Builder"
+      }
+
+      testOptions.junitPlatform.instrumentationTests {
+        enabled true
       }
     }
 
     project.evaluate()
 
     then:
-    def config = ExtensionsKt.findConfiguration(project.configurations, null,
-        ConfigurationKind.ANDROID_TEST, ConfigurationScope.RUNTIME_ONLY)
-    assert config.dependencies.find { it.name == "android-instrumentation-test-runner" } == null
+    def args = project.android.defaultConfig.getTestInstrumentationRunnerArguments()
+    assert args.containsKey("runnerBuilder")
+    assert args["runnerBuilder"].contains("com.something.else.OtherRunnerBuilder")
+    assert args["runnerBuilder"].contains("de.mannodermaus.junit5.AndroidJUnit5Builder")
   }
 
-  def "Instrumentation Test Integration: Runner Library is added automatically if enabled"() {
+  def "Instrumentation Test Integration: Runner Library is added automatically"() {
     when:
     Project project = factory.newProject(rootProject())
         .asAndroidApplication()

android-junit5/src/main/kotlin/de/mannodermaus/gradle/plugins/junit5/Plugin.kt

@@ -128,6 +128,15 @@ class AndroidJUnitPlatformPlugin : Plugin<Project> {
   }
 
   private fun Project.applyConfigurationParameters() {
+    // Verify that the JUnit 5 RunnerBuilder wasn't overwritten by user code,
+    // and if so, throw an exception
+    val actualRunnerBuilder = android.defaultConfig.testInstrumentationRunnerArguments[RUNNER_BUILDER_ARG]!!
+    if (!actualRunnerBuilder.contains(JUNIT5_RUNNER_BUILDER_CLASS_NAME)) {
+      throw IllegalArgumentException(
+          "Custom runnerBuilder is overwriting JUnit 5 integration! " +
+              "Change your declaration to '$actualRunnerBuilder,$JUNIT5_RUNNER_BUILDER_CLASS_NAME'.")
+    }
+
     // Attach runtime-only dependency on JUnit 5 instrumentation test facade
     val defaults = loadProperties(VERSIONS_RESOURCE_NAME)
     val rtOnly = configurations.findConfiguration(kind = ANDROID_TEST, scope = RUNTIME_ONLY)

instrumentation-runner/src/main/kotlin/de/mannodermaus/junit5/Runner.kt

@@ -1,6 +1,7 @@
 package de.mannodermaus.junit5
 
 import org.junit.platform.runner.JUnitPlatform
+import org.junit.runner.Runner
 
 /**
  * JUnit Runner implementation using the JUnit Platform as its backbone.
@@ -14,3 +15,8 @@ import org.junit.platform.runner.JUnitPlatform
  */
 @Suppress("unused")
 internal class AndroidJUnit5(klass: Class<*>) : JUnitPlatform(klass)
+
+/**
+ * Since we can't reference AndroidJUnit5 directly, use this factory for instantiation.
+ */
+internal fun createJUnit5Runner(klass: Class<*>): Runner = AndroidJUnit5(klass)

instrumentation-runner/src/main/kotlin/de/mannodermaus/junit5/RunnerBuilder.kt

@@ -31,26 +31,29 @@ private val jupiterTestAnnotations = listOf(
 @Suppress("unused")
 class AndroidJUnit5Builder : RunnerBuilder() {
 
-  @Suppress("UNCHECKED_CAST")
-  private val runnerClassConstructor by lazy {
-    // We mustn't explicitly reference junit-platform classes
-    // because that would enforce a premature minSdkVersion requirement
-    // on all flavors of a target application.
-    // Instead, an enabled flavor would provide the dependency automatically
-    // through the "instrumentation" library artifact.
-    val klass: Class<Runner> = Class.forName(
-        "de.mannodermaus.junit5.AndroidJUnit5") as Class<Runner>
-    klass.getConstructor(Class::class.java)
+  private val junit5Available by lazy {
+    try {
+      Class.forName("org.junit.jupiter.api.Test")
+      Class.forName("org.junit.jupiter.params.ParameterizedTest")
+      Class.forName("de.mannodermaus.junit5.AndroidJUnit5")
+      true
+    } catch (e: Throwable) {
+      false
+    }
   }
 
   @Throws(Throwable::class)
   override fun runnerForClass(testClass: Class<*>): Runner? {
     try {
+      if (!junit5Available) {
+        return null
+      }
+
       if (!testClass.hasJupiterTestMethods()) {
         return null
       }
 
-      return runnerClassConstructor.newInstance(testClass)
+      return createJUnit5Runner(testClass)
 
     } catch (e: NoClassDefFoundError) {
       Log.e(LOG_TAG, "JUnitPlatform not found on runtime classpath")