new EqualsTester()
        .addEqualityGroup(original, same)
        .addEqualityGroup(reverse)
        .addEqualityGroup(diff2)
        .testEquals();
  }

  public void testMapDifferencePredicateTypical() {
    Map<Integer, String> left = ImmutableMap.of(1, "a", 2, "b", 3, "c", 4, "d", 5, "e");
    Map<Integer, String> right = ImmutableMap.of(1, "A", 3, "F", 5, "G", 6, "Z");