Fix Exec task arg handling and test filter heuristic

- Preserve build-script args in doFirst blocks (LIFO order)
- Fix test filter to only use --select-method for '#' separator
- Update javadoc to reference Exec tasks instead of Test/JavaExec
- Simplify build.gradle.kts to use doFirst (plugin preserves args)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: jbachorik

build-logic/conventions/src/main/kotlin/com/datadoghq/profiler/ProfilerTestPlugin.kt

@@ -141,9 +141,8 @@ class ProfilerTestPlugin : Plugin<Project> {
                 testTask.description = "Runs unit tests with the $configName library variant"
                 testTask.group = "verification"
 
-                // Use JAVA_TEST_HOME if set, otherwise JAVA_HOME
-                val javaHome = System.getenv("JAVA_TEST_HOME") ?: System.getenv("JAVA_HOME")
-                testTask.executable = "$javaHome/bin/java"
+                // Use JAVA_TEST_HOME if set, otherwise JAVA_HOME (with proper fallback and error handling)
+                testTask.executable = PlatformUtils.testJavaExecutable()
 
                 // Dependencies
                 testTask.dependsOn(project.tasks.named("compileTestJava"))
@@ -157,6 +156,8 @@ class ProfilerTestPlugin : Plugin<Project> {
 
                 // Configure JVM arguments and test execution
                 testTask.doFirst {
+                    // Preserve any args added by build scripts (doFirst blocks run in LIFO order)
+                    val buildScriptArgs = testTask.args.toList()
                     val allArgs = mutableListOf<String>()
 
                     // Standard JVM args
@@ -166,6 +167,9 @@ class ProfilerTestPlugin : Plugin<Project> {
                     }
                     allArgs.addAll(extension.extraJvmArgs.get())
 
+                    // Add any args from build scripts (e.g., -Dddprof_test.* properties)
+                    allArgs.addAll(buildScriptArgs)
+
                     // System properties
                     allArgs.add("-DDDPROF_TEST_DISABLE_RATE_LIMIT=1")
                     allArgs.add("-DCI=${project.hasProperty("CI") || System.getenv("CI")?.toBoolean() ?: false}")
@@ -185,6 +189,18 @@ class ProfilerTestPlugin : Plugin<Project> {
                     allArgs.add("--details=verbose")
                     allArgs.add("--details-theme=unicode")
 
+                    // Support Gradle's --tests filter by mapping to JUnit's selection options
+                    if (project.hasProperty("tests")) {
+                        val testFilter = project.property("tests") as String
+                        // Only use --select-method if filter contains '#' (method separator)
+                        // FQCNs contain '.' but should use --select-class
+                        if (testFilter.contains("#")) {
+                            allArgs.add("--select-method=$testFilter")
+                        } else {
+                            allArgs.add("--select-class=$testFilter")
+                        }
+                    }
+
                     testTask.args = allArgs
                 }
 
@@ -223,8 +239,8 @@ class ProfilerTestPlugin : Plugin<Project> {
                     runTask.description = "Run the unwinding validator application ($configName config)"
                     runTask.group = "application"
 
-                    val javaHome = System.getenv("JAVA_TEST_HOME") ?: System.getenv("JAVA_HOME")
-                    runTask.executable = "$javaHome/bin/java"
+                    // Use JAVA_TEST_HOME if set, otherwise JAVA_HOME (with proper fallback and error handling)
+                    runTask.executable = PlatformUtils.testJavaExecutable()
 
                     runTask.dependsOn(project.tasks.named("compileJava"))
                     runTask.dependsOn(mainCfg)
@@ -261,8 +277,8 @@ class ProfilerTestPlugin : Plugin<Project> {
                     reportTask.description = "Generate unwinding report for CI ($configName config)"
                     reportTask.group = "verification"
 
-                    val javaHome = System.getenv("JAVA_TEST_HOME") ?: System.getenv("JAVA_HOME")
-                    reportTask.executable = "$javaHome/bin/java"
+                    // Use JAVA_TEST_HOME if set, otherwise JAVA_HOME (with proper fallback and error handling)
+                    reportTask.executable = PlatformUtils.testJavaExecutable()
 
                     reportTask.dependsOn(project.tasks.named("compileJava"))
                     reportTask.dependsOn(mainCfg)
@@ -372,7 +388,7 @@ abstract class ProfilerTestExtension @Inject constructor(
 ) {
 
     /**
-     * Standard JVM arguments applied to all Test and JavaExec tasks.
+     * Standard JVM arguments applied to all Exec-based test and application tasks.
      * These are the common profiler testing requirements.
      */
     abstract val standardJvmArgs: ListProperty<String>
@@ -384,7 +400,7 @@ abstract class ProfilerTestExtension @Inject constructor(
 
     /**
      * Directory containing native test libraries.
-     * When set, adds -Djava.library.path to Test tasks.
+     * When set, adds -Djava.library.path to test Exec tasks.
      */
     val nativeLibDir: org.gradle.api.file.DirectoryProperty = objects.directoryProperty()
 

ddprof-test/build.gradle.kts

@@ -51,19 +51,22 @@ dependencies {
 }
 
 // Additional test task configuration beyond what the plugin provides
-tasks.withType<Test>().configureEach {
+// The plugin creates Exec tasks (not Test tasks) for config-specific tests
+tasks.withType<org.gradle.api.tasks.Exec>().matching { it.name.startsWith("test") }.configureEach {
   // Ensure native test library is built before running tests
   dependsOn(":ddprof-test-native:linkLib")
 
-  // Extract config name from task name for test-specific JVM args
+  // Extract config name from task name for test-specific system properties
   val configName = name.replace("test", "")
   val keepRecordings = project.hasProperty("keepJFRs") || System.getenv("KEEP_JFRS")?.toBoolean() ?: false
 
-  jvmArgs(
-    "-Dddprof_test.keep_jfrs=$keepRecordings",
-    "-Dddprof_test.config=$configName",
-    "-Dddprof_test.ci=${project.hasProperty("CI")}",
-  )
+  // Pass test configuration as system properties
+  // The plugin's doFirst preserves args added here (doFirst blocks run in LIFO order)
+  doFirst {
+    args("-Dddprof_test.keep_jfrs=$keepRecordings")
+    args("-Dddprof_test.config=$configName")
+    args("-Dddprof_test.ci=${project.hasProperty("CI")}")
+  }
 }
 
 // Disable the default 'test' task - we use config-specific tasks instead