@Test
public void testDifference() {

    IElectronContainer ec1 = mock(IElectronContainer.class);
    IElectronContainer ec2 = mock(IElectronContainer.class);
    when(ec1.getElectronCount()).thenReturn(2);
    when(ec2.getElectronCount()).thenReturn(3);
    IDifference difference = ElectronContainerDiff.difference(ec1, ec2);
    Assert.assertNotNull(difference);
}