Add unit tests for write-filters task & fix a bug with generating the…

… filters file for instrumentation tests

plugin/android-junit5/src/main/kotlin/de/mannodermaus/gradle/plugins/junit5/tasks/AndroidJUnit5WriteFilters.kt

@@ -83,8 +83,8 @@ public abstract class AndroidJUnit5WriteFilters : DefaultTask() {
                     .bufferedWriter()
                     .use { writer ->
                         // This format is a nod towards the real JUnit 5 ConsoleLauncher's arguments
-                        includeTags.forEach { tag -> writer.write("-t $tag") }
-                        excludeTags.forEach { tag -> writer.write("-T $tag") }
+                        includeTags.forEach { tag -> writer.appendLine("-t $tag") }
+                        excludeTags.forEach { tag -> writer.appendLine("-T $tag") }
                     }
             }
         }

plugin/android-junit5/src/test/kotlin/de/mannodermaus/gradle/plugins/junit5/plugin/InstrumentationSupportTests.kt

@@ -165,6 +165,16 @@ class InstrumentationSupportTests {
         assertThat(project).configuration("androidTestRuntimeOnly").hasDependency(runnerLibrary())
     }
 
+    @Test
+    fun `register the filter-write tasks`() {
+        project.addJUnitJupiterApi()
+        project.evaluate()
+
+        // AGP only registers androidTest tasks for the debug build type
+        assertThat(project).task("writeFiltersDebugAndroidTest").exists()
+        assertThat(project).task("writeFiltersReleaseAndroidTest").doesNotExist()
+    }
+
     /* Private */
 
     private fun Project.addJUnitJupiterApi() {

plugin/android-junit5/src/test/kotlin/de/mannodermaus/gradle/plugins/junit5/tasks/AndroidJUnit5WriteFiltersTests.kt

@@ -0,0 +1,77 @@
+package de.mannodermaus.gradle.plugins.junit5.tasks
+
+import com.google.common.truth.Truth.assertThat
+import de.mannodermaus.gradle.plugins.junit5.internal.config.INSTRUMENTATION_FILTER_RES_FILE_NAME
+import de.mannodermaus.gradle.plugins.junit5.plugin.TestProjectProviderExtension
+import de.mannodermaus.gradle.plugins.junit5.util.assertAll
+import de.mannodermaus.gradle.plugins.junit5.util.evaluate
+import org.gradle.api.Project
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.extension.RegisterExtension
+import java.io.File
+import java.nio.file.Paths
+import kotlin.io.path.readLines
+
+class AndroidJUnit5WriteFiltersTests {
+    @RegisterExtension
+    @JvmField
+    val projectExtension = TestProjectProviderExtension()
+
+    private lateinit var project: Project
+
+    @BeforeEach
+    fun beforeEach() {
+        project = projectExtension.newProject()
+            .asAndroidApplication()
+            .applyJUnit5Plugin(true) { junitPlatform ->
+                junitPlatform.filters().includeTags("included")
+                junitPlatform.filters().excludeTags("excluded", "another-group")
+            }
+            .build()
+        project.evaluate()
+    }
+
+    @Test
+    fun `generates file structure correctly`() {
+        // Expect a 'raw' folder inside the output, then the actual filters file in that sub-folder
+        val output = project.runTaskAndGetOutputFolder()
+
+        File(output, "raw").apply {
+            assertAll(
+                "output contains 'raw' folder",
+                { assertThat(exists()).isTrue() },
+                { assertThat(isDirectory).isTrue() },
+            )
+
+            File(this, INSTRUMENTATION_FILTER_RES_FILE_NAME).apply {
+                assertAll(
+                    "'raw' folder contains filters file'",
+                    { assertThat(exists()).isTrue() },
+                    { assertThat(isFile).isTrue() },
+                )
+            }
+        }
+    }
+
+    @Test
+    fun `file contains expected content`() {
+        val output = project.runTaskAndGetOutputFolder()
+        val file = Paths.get(output.absolutePath, "raw", INSTRUMENTATION_FILTER_RES_FILE_NAME)
+
+        val content = file.readLines()
+        assertThat(content).containsExactly(
+            "-t included",
+            "-T excluded",
+            "-T another-group",
+        )
+    }
+
+    /* Private */
+
+    private fun Project.runTaskAndGetOutputFolder(): File {
+        val task = project.tasks.getByName("writeFiltersDebugAndroidTest") as AndroidJUnit5WriteFilters
+        task.execute()
+        return requireNotNull(task.outputFolder)
+    }
+}

plugin/android-junit5/src/test/kotlin/de/mannodermaus/gradle/plugins/junit5/util/GradleTruth.kt

@@ -3,8 +3,10 @@ package de.mannodermaus.gradle.plugins.junit5.util
 import com.google.common.truth.FailureMetadata
 import com.google.common.truth.Subject
 import com.google.common.truth.Truth
+import com.google.common.truth.Truth.assertThat
 import com.google.common.truth.Truth.assertWithMessage
 import org.gradle.api.Project
+import org.gradle.api.Task
 import org.gradle.api.artifacts.Configuration
 
 /* Methods */
@@ -22,6 +24,10 @@ class ProjectSubject(
     fun configuration(name: String): ConfigurationSubject = check("configuration()")
         .about(::ConfigurationSubject)
         .that(actual?.configurations?.getByName(name))
+
+    fun task(name: String): TaskSubject = check("task()")
+        .about(::TaskSubject)
+        .that(actual?.tasks?.findByName(name))
 }
 
 class ConfigurationSubject(
@@ -66,3 +72,16 @@ class ConfigurationSubject(
         ).that(hasMatch).isEqualTo(expectExists)
     }
 }
+
+class TaskSubject(
+    metadata: FailureMetadata,
+    private val actual: Task?,
+) : Subject(metadata, actual) {
+    fun exists() {
+        assertThat(actual).isNotNull()
+    }
+
+    fun doesNotExist() {
+        assertThat(actual).isNull()
+    }
+}

plugin/android-junit5/src/test/kotlin/de/mannodermaus/gradle/plugins/junit5/util/projects/PluginSpecProjectCreator.kt

@@ -1,6 +1,8 @@
 package de.mannodermaus.gradle.plugins.junit5.util.projects
 
+import de.mannodermaus.gradle.plugins.junit5.dsl.AndroidJUnitPlatformExtension
 import de.mannodermaus.gradle.plugins.junit5.internal.extensions.android
+import de.mannodermaus.gradle.plugins.junit5.internal.extensions.junitPlatform
 import de.mannodermaus.gradle.plugins.junit5.util.TestEnvironment
 import de.mannodermaus.gradle.plugins.junit5.util.applyPlugin
 import de.mannodermaus.gradle.plugins.junit5.util.evaluate
@@ -40,7 +42,7 @@ class PluginSpecProjectCreator(private val environment: TestEnvironment) {
 
         private var projectType = Type.Unset
         private var appId = "com.example.android"
-        private var applyJUnit5Plugin = true
+        private var applyJUnit5Plugin: ((AndroidJUnitPlatformExtension) -> Unit)? = {}
         private var applyJacocoPlugin = false
         private var applyKotlinPlugin = false
 
@@ -60,8 +62,12 @@ class PluginSpecProjectCreator(private val environment: TestEnvironment) {
 
         fun asAndroidLibrary() = setProjectTypeIfUnsetTo(Type.Library)
 
-        fun applyJUnit5Plugin(state: Boolean = true) = apply {
-            this.applyJUnit5Plugin = state
+        fun applyJUnit5Plugin(state: Boolean = true, configuration: ((AndroidJUnitPlatformExtension) -> Unit)? = null) = apply {
+            this.applyJUnit5Plugin = if (state) {
+                configuration ?: {}
+            } else {
+                null
+            }
         }
 
         fun applyJacocoPlugin(state: Boolean = true) = apply {
@@ -93,7 +99,7 @@ class PluginSpecProjectCreator(private val environment: TestEnvironment) {
                 project.applyPlugin("kotlin-android")
             }
 
-            if (applyJUnit5Plugin) {
+            if (applyJUnit5Plugin != null) {
                 project.applyPlugin("de.mannodermaus.android-junit5")
             }
 
@@ -116,6 +122,14 @@ class PluginSpecProjectCreator(private val environment: TestEnvironment) {
                 // swallow this particular error
             }
 
+            // Configure JUnit 5 with custom configuration clause, if any
+            try {
+                applyJUnit5Plugin?.invoke(project.junitPlatform)
+            } catch (e: UnknownDomainObjectException) {
+                // Expected when the JUnit 5 plugin is not applied to a project;
+                // swallow this particular error
+            }
+
             return project
         }