@Test
public void testDiff() {

    IElement element1 = mock(IElement.class);
    IElement element2 = mock(IElement.class);
    when(element1.getSymbol()).thenReturn("H");
    when(element2.getSymbol()).thenReturn("C");
    String result = ElementDiff.diff(element1, element2);
    Assert.assertNotNull(result);
    Assert.assertNotSame(0, result.length());
    assertContains(result, "ElementDiff");
    assertContains(result, "H/C");
}