Refactored buildSrc Gradle-based tests around GradleFixture and reduce resource use.

buildSrc/src/main/kotlin/datadog/gradle/plugin/muzzle/MuzzleMavenRepoUtils.kt

@@ -20,13 +20,16 @@ import java.nio.file.Files
 
 internal object MuzzleMavenRepoUtils {
   /**
-   * Remote repositories used to query version ranges and fetch dependencies
+   * Remote repositories used to query version ranges and fetch dependencies.
+   *
+   * This intentionally reads the environment on each access: Gradle daemons can
+   * be reused across builds with different MAVEN_REPOSITORY_PROXY values.
    */
   @JvmStatic
-  val MUZZLE_REPOS: List<RemoteRepository> by lazy {
+  fun defaultMuzzleRepos(): List<RemoteRepository> {
     val central = RemoteRepository.Builder("central", "default", "https://repo1.maven.org/maven2/").build()
     val mavenProxyUrl = System.getenv("MAVEN_REPOSITORY_PROXY")
-    if (mavenProxyUrl == null) {
+    return if (mavenProxyUrl == null) {
       listOf(central)
     } else {
       val proxy = RemoteRepository.Builder("central-proxy", "default", mavenProxyUrl).build()
@@ -70,7 +73,7 @@ internal object MuzzleMavenRepoUtils {
     muzzleDirective: MuzzleDirective,
     system: RepositorySystem,
     session: RepositorySystemSession,
-    defaultRepos: List<RemoteRepository> = MUZZLE_REPOS
+    defaultRepos: List<RemoteRepository> = defaultMuzzleRepos()
   ): Set<MuzzleDirective> {
     val allVersionsArtifact = DefaultArtifact(
       muzzleDirective.group,
@@ -124,7 +127,7 @@ internal object MuzzleMavenRepoUtils {
     muzzleDirective: MuzzleDirective,
     system: RepositorySystem,
     session: RepositorySystemSession,
-    defaultRepos: List<RemoteRepository> = MUZZLE_REPOS
+    defaultRepos: List<RemoteRepository> = defaultMuzzleRepos()
   ): VersionRangeResult {
     val directiveArtifact: Artifact = DefaultArtifact(
       muzzleDirective.group,

buildSrc/src/test/kotlin/datadog/gradle/plugin/GradleFixture.kt

@@ -1,9 +1,11 @@
 package datadog.gradle.plugin
 
+import datadog.gradle.plugin.GradleFixture.Companion.sharedTestKitDir
 import org.gradle.testkit.runner.BuildResult
 import org.gradle.testkit.runner.GradleRunner
 import org.gradle.testkit.runner.UnexpectedBuildResultException
 import org.intellij.lang.annotations.Language
+import org.junit.jupiter.api.io.TempDir
 import org.w3c.dom.Document
 import java.io.File
 import java.nio.file.Files
@@ -13,132 +15,207 @@ import javax.xml.parsers.DocumentBuilderFactory
  * Base fixture for Gradle plugin integration tests.
  * Provides common functionality for setting up test projects and running Gradle builds.
  */
-internal open class GradleFixture(protected val projectDir: File) {
-  // Each fixture gets its own testkit dir in the system temp directory (NOT under
-  // projectDir) so that JUnit's @TempDir cleanup doesn't race with daemon file locks.
-  // See https://github.com/gradle/gradle/issues/12535
-  // A fresh daemon is started per test — ensuring withEnvironment() vars (e.g.
-  // MAVEN_REPOSITORY_PROXY) are correctly set on the daemon JVM and not inherited
-  // from a previously-started daemon with a different test's environment.
-  // A JVM shutdown hook removes the directory after all tests have run (and daemons
-  // have been stopped), so file locks are guaranteed to be released by then.
-  private val testKitDir: File by lazy {
-    Files.createTempDirectory("gradle-testkit-").toFile().also { dir ->
-      Runtime.getRuntime().addShutdownHook(Thread { dir.deleteRecursively() })
+open class GradleFixture {
+  @TempDir
+  protected lateinit var projectDir: File
+
+  private val testKitDir: File get() = sharedTestKitDir
+
+  companion object {
+    // JVM-wide testkit dir shared across all GradleFixture instances. One daemon
+    // pool serves every test method, so kotlinc work on .gradle.kts scripts is
+    // amortized instead of re-paid per test (recovers the +77 % wall-time
+    // regression introduced by the Groovy→Kotlin DSL conversion).
+    //
+    // Lives outside any @TempDir so JUnit cleanup never races with daemon file
+    // locks. See https://github.com/gradle/gradle/issues/12535
+    //
+    // TestKit may reuse the same daemon for builds with different withEnvironment()
+    // values, so build logic must not cache environment-derived state in daemon-static
+    // fields.
+    private val sharedTestKitDir: File by lazy {
+      Files.createTempDirectory("gradle-testkit-").toFile().also { dir ->
+        Runtime.getRuntime().addShutdownHook(Thread {
+          stopDaemonsIn(dir)
+          dir.deleteRecursively()
+        })
+      }
+    }
+
+    /**
+     * Kills Gradle daemons started by TestKit under the given testkit dir.
+     *
+     * The Gradle Tooling API (used by [GradleRunner]) always spawns a daemon and
+     * provides no public API to stop it (https://github.com/gradle/gradle/issues/12535).
+     * We replicate the strategy Gradle uses in its own integration tests
+     * ([DaemonLogsAnalyzer.killAll()][1]):
+     *
+     * 1. Scan `<testkit>/daemon/<version>/` for log files matching
+     *    `DaemonLogConstants.DAEMON_LOG_PREFIX + pid + DaemonLogConstants.DAEMON_LOG_SUFFIX`,
+     *    i.e. `daemon-<pid>.out.log`.
+     * 2. Extract the PID from the filename and kill the process.
+     *
+     * Trade-offs of the PID-from-filename approach:
+     * - **PID recycling**: between the build finishing and `kill` being sent, the OS
+     *   could theoretically recycle the PID.  Now that this only runs at JVM exit
+     *   (no longer per-test), the window is short — when called from the shutdown
+     *   hook all daemons we own are still alive — so the risk remains negligible.
+     * - **Filename convention is internal**: Gradle's `DaemonLogConstants.DAEMON_LOG_PREFIX`
+     *   (`"daemon-"`) / `DAEMON_LOG_SUFFIX` (`".out.log"`) are not public API; a future
+     *   Gradle version could change them.  The `toLongOrNull()` guard safely skips entries
+     *   that don't parse as a PID (including the UUID fallback Gradle uses when the PID
+     *   is unavailable).
+     * - **Java 8 compatible**: uses `kill`/`taskkill` via [ProcessBuilder] instead of
+     *   `ProcessHandle` (Java 9+) because build logic targets JVM 1.8.
+     *
+     * [1]: https://github.com/gradle/gradle/blob/43b381d88/testing/internal-distribution-testing/src/main/groovy/org/gradle/integtests/fixtures/daemon/DaemonLogsAnalyzer.groovy
+     */
+    private fun stopDaemonsIn(testKitDir: File) {
+      val daemonDir = File(testKitDir, "daemon")
+      if (!daemonDir.exists()) return
+
+      daemonDir.walkTopDown()
+        .filter { it.isFile && it.name.endsWith(".out.log") && !it.name.startsWith("hs_err") }
+        .forEach { logFile ->
+          val pid = logFile.nameWithoutExtension  // daemon-12345.out
+            .removeSuffix(".out")                 // daemon-12345
+            .removePrefix("daemon-")              // 12345
+            .toLongOrNull() ?: return@forEach     // skip UUIDs / unparseable names
+
+          val isWindows = System.getProperty("os.name").lowercase().contains("win")
+          val killProcess = if (isWindows) {
+            ProcessBuilder("taskkill", "/F", "/PID", pid.toString())
+          } else {
+            ProcessBuilder("kill", pid.toString())
+          }
+          try {
+            val process = killProcess.redirectErrorStream(true).start()
+            process.waitFor(5, java.util.concurrent.TimeUnit.SECONDS)
+          } catch (_: Exception) {
+            // best effort — daemon may already be stopped
+          }
+        }
     }
   }
 
   /**
    * Runs Gradle with the specified arguments.
    *
-   * After the build completes, any Gradle daemons started by TestKit are killed
-   * so their file locks on the testkit cache are released before JUnit `@TempDir`
-   * cleanup.  See https://github.com/gradle/gradle/issues/12535
+   * The TestKit daemon spawned by the first call and reused for every subsequent
+   * call in the JVM (shared [testKitDir]) so Kotlin compilation of `.gradle.kts`
+   * scripts amortizes across tests instead of being re-paid per test.
+   * Daemons are reaped at JVM shutdown by the hook registered when
+   * [sharedTestKitDir] is created.
    *
    * @param args Gradle task names and arguments
    * @param expectFailure Whether the build is expected to fail
    * @param env Environment variables to set (merged with system environment)
+   * @param forwardOutput Forward the build's stdout/stderr to the test's output
+   * @param gradleProjectDir Override the project directory used by Gradle (useful for git worktree tests);
+   *     defaults to the fixture's project directory.
    * @return The build result
    */
-  fun run(vararg args: String, expectFailure: Boolean = false, env: Map<String, String> = emptyMap()): BuildResult {
+  fun run(
+    vararg args: String,
+    expectFailure: Boolean = false,
+    env: Map<String, String> = emptyMap(),
+    forwardOutput: Boolean = false,
+    gradleProjectDir: File = projectDir,
+  ): BuildResult {
     val runner = GradleRunner.create()
       .withTestKitDir(testKitDir)
       .withPluginClasspath()
-      .withProjectDir(projectDir)
+      .withProjectDir(gradleProjectDir)
       // Using withDebug prevents starting a daemon, but it doesn't work with withEnvironment
       .withEnvironment(System.getenv() + env)
       .withArguments(*args)
+    if (forwardOutput) {
+      runner.forwardOutput()
+    }
     return try {
       if (expectFailure) runner.buildAndFail() else runner.build()
     } catch (e: UnexpectedBuildResultException) {
       e.buildResult
-    } finally {
-      stopDaemons()
     }
   }
 
   /**
-   * Kills Gradle daemons started by TestKit for this fixture's testkit dir.
-   *
-   * The Gradle Tooling API (used by [GradleRunner]) always spawns a daemon and
-   * provides no public API to stop it (https://github.com/gradle/gradle/issues/12535).
-   * We replicate the strategy Gradle uses in its own integration tests
-   * ([DaemonLogsAnalyzer.killAll()][1]):
-   *
-   * 1. Scan `<testkit>/daemon/<version>/` for log files matching
-   *    `DaemonLogConstants.DAEMON_LOG_PREFIX + pid + DaemonLogConstants.DAEMON_LOG_SUFFIX`,
-   *    i.e. `daemon-<pid>.out.log`.
-   * 2. Extract the PID from the filename and kill the process.
+   * Writes a file under the project directory, creating parent dirs as needed.
    *
-   * Trade-offs of the PID-from-filename approach:
-   * - **PID recycling**: between the build finishing and `kill` being sent, the OS
-   *   could theoretically recycle the PID.  In practice the window is short
-   *   (the `finally` block runs immediately after the build) so the risk is negligible.
-   * - **Filename convention is internal**: Gradle's `DaemonLogConstants.DAEMON_LOG_PREFIX`
-   *   (`"daemon-"`) / `DAEMON_LOG_SUFFIX` (`".out.log"`) are not public API; a future
-   *   Gradle version could change them.  The `toLongOrNull()` guard safely skips entries
-   *   that don't parse as a PID (including the UUID fallback Gradle uses when the PID
-   *   is unavailable).
-   * - **Java 8 compatible**: uses `kill`/`taskkill` via [ProcessBuilder] instead of
-   *   `ProcessHandle` (Java 9+) because build logic targets JVM 1.8.
-   *
-   * [1]: https://github.com/gradle/gradle/blob/43b381d88/testing/internal-distribution-testing/src/main/groovy/org/gradle/integtests/fixtures/daemon/DaemonLogsAnalyzer.groovy
+   * @param path Path relative to the project directory
+   * @param content File contents; passed through [String.trimIndent] before writing,
+   *                and a trailing newline is appended.
+   * @param append If true, appends to any existing file instead of overwriting it.
+   *               Safe to call repeatedly to build content up across steps.
    */
-  private fun stopDaemons() {
-    val daemonDir = File(testKitDir, "daemon")
-    if (!daemonDir.exists()) return
-
-    daemonDir.walkTopDown()
-      .filter { it.isFile && it.name.endsWith(".out.log") && !it.name.startsWith("hs_err") }
-      .forEach { logFile ->
-        val pid = logFile.nameWithoutExtension  // daemon-12345.out
-          .removeSuffix(".out")                 // daemon-12345
-          .removePrefix("daemon-")              // 12345
-          .toLongOrNull() ?: return@forEach     // skip UUIDs / unparseable names
-
-        val isWindows = System.getProperty("os.name").lowercase().contains("win")
-        val killProcess = if (isWindows) {
-          ProcessBuilder("taskkill", "/F", "/PID", pid.toString())
-        } else {
-          ProcessBuilder("kill", pid.toString())
-        }
-        try {
-          val process = killProcess.redirectErrorStream(true).start()
-          process.waitFor(5, java.util.concurrent.TimeUnit.SECONDS)
-        } catch (_: Exception) {
-          // best effort — daemon may already be stopped
-        }
-      }
-  }
+  fun writeFile(path: String, content: String, append: Boolean = false): File =
+    file(path).also {
+      it.parentFile?.mkdirs()
+      val text = content.trimIndent() + "\n"
+      if (append) it.appendText(text) else it.writeText(text)
+    }
 
   /**
-   * Adds a subproject to the build.
-   * Updates settings.gradle and creates the build script for the subproject.
+   * Adds a subproject to the build by appending an `include` line to settings.gradle.kts
+   * and writing the subproject's build.gradle.kts.
    *
    * @param projectPath The project path (e.g., "dd-java-agent:instrumentation:other")
    * @param buildScript The build script content for the subproject
    */
-  fun addSubproject(projectPath: String, @Language("Groovy") buildScript: String) {
-    // Add to settings.gradle
-    val settingsFile = file("settings.gradle")
-    if (settingsFile.exists()) {
-      settingsFile.appendText("\ninclude ':$projectPath'")
-    } else {
-      settingsFile.writeText("include ':$projectPath'")
-    }
+  fun addSubproject(projectPath: String, @Language("kotlin") buildScript: String) {
+    writeFile("settings.gradle.kts", """include(":$projectPath")""", append = true)
+    writeFile("${projectPath.replace(':', '/')}/build.gradle.kts", buildScript)
+  }
 
-    file("${projectPath.replace(':', '/')}/build.gradle")
-      .writeText(buildScript.trimIndent())
+  /**
+   * Writes a Java source file under src/<sourceSet>/java.
+   *
+   * @param classNameOrPath Simple class name, fully qualified class name, or source path
+   * @param sourceCode The Java source content
+   * @param sourceSet The Gradle source set to write to
+   * @param projectPath Optional Gradle project path; defaults to the root project
+   */
+  fun writeJavaSource(
+    classNameOrPath: String,
+    @Language("JAVA") sourceCode: String,
+    sourceSet: String = "main",
+    projectPath: String? = null,
+  ) {
+    val sourcePath = classNameOrPath.removeSuffix(".java").replace('.', '/') + ".java"
+    val projectPrefix = projectPath
+      ?.removePrefix(":")
+      ?.replace(':', '/')
+      ?.let { "$it/" }
+      .orEmpty()
+    writeFile("${projectPrefix}src/$sourceSet/java/$sourcePath", sourceCode)
   }
 
   /**
-   * Writes the root project's build.gradle file.
+   * Writes gradle.properties at the project root.
+   *
+   * @param content Properties content (trimIndent applied, trailing newline added)
+   * @param append If true, appends to any existing file instead of overwriting
+   */
+  fun writeGradleProperties(content: String, append: Boolean = false): File =
+    writeFile("gradle.properties", content, append)
+
+  /**
+   * Writes the root project's build.gradle.kts file.
    *
    * @param buildScript The build script content for the root project
+   * @param append If true, appends to any existing file instead of overwriting
    */
-  fun writeRootProject(@Language("Groovy") buildScript: String) {
-    file("build.gradle").writeText(buildScript.trimIndent())
-  }
+  fun writeRootProject(@Language("kotlin") buildScript: String, append: Boolean = false): File =
+    writeFile("build.gradle.kts", buildScript, append)
+
+  /**
+   * Writes the root project's settings.gradle.kts file.
+   *
+   * @param settingsScript The settings script content
+   * @param append If true, appends to any existing file instead of overwriting
+   */
+  fun writeSettings(@Language("kotlin") settingsScript: String, append: Boolean = false): File =
+    writeFile("settings.gradle.kts", settingsScript, append)
 
   /**
    * Parses an XML file into a DOM Document.
@@ -149,12 +226,26 @@ internal open class GradleFixture(protected val projectDir: File) {
   }
 
   /**
-   * Creates or gets a file in the project directory, ensuring parent directories exist.
+   * Returns a File handle under the project directory.
+   * Does not touch the filesystem.
    */
-  protected fun file(path: String, mkdirs: Boolean = true): File =
-    File(projectDir, path).also { file ->
-      if (mkdirs) {
-        file.parentFile?.mkdirs()
-      }
-    }
+  fun file(path: String): File = File(projectDir, path)
+
+  /**
+   * Creates a directory under the project directory (including any missing parents)
+   * and returns it.
+   */
+  fun dir(path: String): File = file(path).also { it.mkdirs() }
+
+  /**
+   * The Gradle build output directory (`projectDir/build`). Not created — Gradle
+   * produces it during a build.
+   */
+  val buildDir: File get() = File(projectDir, "build")
+
+  /**
+   * Returns a File under the Gradle build output directory (`projectDir/build/...`).
+   * Does NOT create parent dirs — these paths are read after a Gradle build produces them.
+   */
+  fun buildFile(path: String): File = File(buildDir, path)
 }