@Test
 public void shouldParseMutationEnigne() {
   final ReportOptions actual = parseAddingRequiredArgs("--mutationEngine", "foo");
   assertEquals("foo", actual.getMutationEngine());
 }
 @Test
 public void shouldDefaultToGregorEngineWhenNoOptionSupplied() {
   final ReportOptions actual = parseAddingRequiredArgs();
   assertEquals("gregor", actual.getMutationEngine());
 }