EqualsVerifier can be used in Java unit tests to verify whether the contract for the equals and hashCode methods is met.

When migrating from EqualsVerifier 1 to 2, there are a few things you should be aware of. (See also the changelog).

  • EqualsVerifier 2 no longer supports Java 6. Don’t upgrade if you’re still using Java 6.
  • EqualsVerifier.forExamples has been removed, because over time, EqualsVerifier has been ignoring the given examples more and more anyway, favouring forClass style checks instead. There were also occasional problems when the given examples were of inconsistent types. Therefore, in almost all cases, you can use EqualsVerifier.forClass instead. In the rare cases when that doesn’t work, you can also use EqualsVerifier.forRelaxedEqualExamples.
  • EqualsVerifier 1 has a switch allFieldsShouldBeUsed(), which has now become the default behaviour. This means that EqualsVerifier expects that all non-static fields in the class are actually used in the equals method, and fails if this isn’t the case. In most cases, this should not matter. If you do have fields in your class that shouldn’t be used in equals, you can tell EqualsVerifier to ignore them individually by calling #withIgnoredFields, or revert to the old behaviour by suppressing Warning.ALL_FIELDS_SHOULD_BE_USED.
  • EqualsVerifier now fails if you don’t actually override equals in your class, because this might signal that you intend to override equals, but forgot. If this is not the case (for instance, if you ‘sweep’ a whole package where most classes override equals but one doesn’t), you can revert to the old behaviour by suppressing Warning.INHERITED_DIRECTLY_FROM_OBJECT.
  • EqualsVerifier is now smarter when it comes to type erasure. In many cases where you had to call withPrefabValues for a generic type to work around a ClassCastException in EqualsVerifier, this is no longer necessary. An example of this is Android’s SparseArray class.

If you encounter any other problems, please let me know in the issue tracker.