[hotfix] Make TestExecutorResource generic in the ExecutorService

Making the TestExecutorResource generic in the ExecutorService has the advantage that the resource
can also manage and return SchedulerExecutorServices.

flink-runtime/src/test/java/org/apache/flink/runtime/taskexecutor/TaskExecutorPartitionLifecycleTest.java

@@ -118,8 +118,8 @@ public class TaskExecutorPartitionLifecycleTest extends TestLogger {
  @Rule public final TemporaryFolder tmp = new TemporaryFolder();
 
  @ClassRule
- public static final TestExecutorResource TEST_EXECUTOR_SERVICE_RESOURCE =
- new TestExecutorResource(() -> java.util.concurrent.Executors.newFixedThreadPool(1));
+ public static final TestExecutorResource<?> TEST_EXECUTOR_SERVICE_RESOURCE =
+ new TestExecutorResource<>(() -> java.util.concurrent.Executors.newFixedThreadPool(1));
 
  @Before
  public void setup() {

flink-test-utils-parent/flink-test-utils-junit/src/main/java/org/apache/flink/testutils/executor/TestExecutorResource.java

@@ -19,18 +19,17 @@
 
 import org.junit.rules.ExternalResource;
 
-import java.util.concurrent.Executor;
 import java.util.concurrent.ExecutorService;
 import java.util.function.Supplier;
 
 /** Resource which starts/stops an {@link ExecutorService} for testing purposes. */
-public class TestExecutorResource extends ExternalResource {
+public class TestExecutorResource<T extends ExecutorService> extends ExternalResource {
 
- private final Supplier<ExecutorService> serviceFactory;
+ private final Supplier<T> serviceFactory;
 
- private ExecutorService executorService;
+ private T executorService;
 
- public TestExecutorResource(Supplier<ExecutorService> serviceFactory) {
+ public TestExecutorResource(Supplier<T> serviceFactory) {
  this.serviceFactory = serviceFactory;
  }
 
@@ -39,7 +38,7 @@ protected void before() throws Throwable {
  executorService = serviceFactory.get();
  }
 
- public Executor getExecutor() {
+ public T getExecutor() {
  // only return an Executor since this resource is in charge of the life cycle
  return executorService;
  }