Fix observationShouldNotLeakToFutureCompletionThread again

Signed-off-by: pema4 <[email protected]>

Author: pema4

samples/micrometer-samples-spring-framework6/src/test/java/io/micrometer/samples/spring6/aop/ObservedAspectTests.java

@@ -179,20 +179,14 @@ void observationShouldNotLeakToFutureCompletionThread() {
         ObservedService service = pf.getProxy();
         FakeAsyncTask fakeAsyncTask = new FakeAsyncTask("test-result");
 
-        ThreadPoolExecutor sameThreadExecutor = new ThreadPoolExecutor(1, 1, 60, TimeUnit.SECONDS,
-                new LinkedBlockingQueue<>());
-        try {
-            CompletableFuture<String> asyncResult = service
-                .parent(() -> service.asyncChild(fakeAsyncTask, sameThreadExecutor));
-            CompletableFuture<Void> asyncAssertion = asyncResult.thenRunAsync(
-                    () -> assertThat(registry).doesNotHaveAnyRemainingCurrentObservation(), sameThreadExecutor);
-            fakeAsyncTask.proceed();
-
-            assertThat(asyncAssertion).succeedsWithin(Duration.ofMillis(200));
-        }
-        finally {
-            sameThreadExecutor.shutdown();
-        }
+        ExecutorService sameThreadExecutor = Executors.newSingleThreadExecutor();
+        CompletableFuture<String> asyncResult = service
+            .parent(() -> service.asyncChild(fakeAsyncTask, sameThreadExecutor));
+        CompletableFuture<Void> asyncAssertion = asyncResult
+            .thenRunAsync(() -> assertThat(registry).doesNotHaveAnyRemainingCurrentObservation(), sameThreadExecutor);
+        fakeAsyncTask.proceed();
+
+        assertThat(asyncAssertion).succeedsWithin(Duration.ofMillis(200));
     }
 
     @Test