@Test
public void testMatchAgainstItself() {

    IAtomContainer container = mock(IAtomContainer.class);
    when(container.getElectronContainerCount()).thenReturn(1);
    when(container.getElectronContainer(0)).thenReturn(mock(IBond.class));
    String result = AtomContainerDiff.diff(container, container);
    assertZeroLength(result);
}