@Test
public void testPermutation_TwoSubstituents() throws Exception {

    PermutationParity p = permutation(new int[]{1, 2, 0});
    assertTrue(p instanceof BasicPermutationParity);
    Field field = p.getClass().getDeclaredField("indices");
    field.setAccessible(true);
    assertArrayEquals((int[]) field.get(p), new int[]{1, 2});
}