@Test
  public void unregisterListenersWithNullSignalThrowsNullPointerException() {
    assertThatThrownBy(() -> createSignalNotificationHandler().unregisterListeners(null))
        .isInstanceOf(NullPointerException.class)
        .hasMessage("The signal from which to unregister all listeners cannot be null!");
  }
Unit tests for {@link AbstractSignalNotificationHandler}.

@since GemFire 7.0
geode-core/src/test/java/org/apache/geode/internal/process/signal/AbstractSignalNotificationHandlerTest.java