@Test
  public void isClosed_returnsTrue_ifCacheIsClosed() {
    gemFireCacheImpl = gemFireCacheImpl(false);

    gemFireCacheImpl.close();

    assertThat(gemFireCacheImpl.isClosed())
        .isTrue();
  }
Unit tests for closing {@link GemFireCacheImpl}.
geode-core/src/test/java/org/apache/geode/internal/cache/GemFireCacheImplCloseTest.java