@Test
  public void oneThread() {
    executorServiceRule.submit(() -> terminateLatch.await(TIMEOUT_MILLIS, MILLISECONDS));

    assertThat(executorServiceRule.getThreads()).hasSize(1);
  }
Unit tests for {@link ExecutorServiceRule#getThreads()}.
geode-junit/src/test/java/org/apache/geode/test/junit/rules/ExecutorServiceRuleGetThreadsTest.java