@Test
  public void registerListenerWithNullSignalListenerThrowsNullPointerException() {
    assertThatThrownBy(() -> createSignalNotificationHandler().registerListener(null))
        .isInstanceOf(NullPointerException.class)
        .hasMessage("The SignalListener to register, listening for all signals 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