Recursive assertions

The recursive assertion allFieldsSatisfy lets you verify a Predicate is met for all the fields of the object under test graph recursively (but not the object itself).

For example if the object under test is an instance of class A, A has a B field and B a C field then allFieldsSatisfy checks A’s B field and B’s C field and all C’s fields.

Example:

class Author {
  String name;
  String email;
  List<Book> books = new ArrayList<>();

  Author(String name, String email) {
    this.name = name;
    this.email = email;
  }
}

class Book {
  String title;
  Author[] authors;

  Book(String title, Author[] authors) {
    this.title = title;
    this.authors = authors;
  }
}

Author pramodSadalage = new Author("Pramod Sadalage", "p.sadalage@recursive.test");
Author martinFowler = new Author("Martin Fowler", "m.fowler@recursive.test");
Author kentBeck = new Author("Kent Beck", "k.beck@recursive.test");

Book noSqlDistilled = new Book("NoSql Distilled", new Author[] {pramodSadalage, martinFowler});
pramodSadalage.books.add(noSqlDistilled);
martinFowler.books.add(noSqlDistilled);

Book refactoring = new Book("Refactoring", new Author[] {martinFowler, kentBeck});
martinFowler.books.add(refactoring);
kentBeck.books.add(refactoring);

// assertion succeeds
assertThat(pramodSadalage).usingRecursiveAssertion()
                          .allFieldsSatisfy(field -> field != null);

The above example is best rewritten with hasNoNullFields() which is common enough that it is supported out of the box.

The recursive assertion provides these methods to exclude fields, the predicate won’t be applied on the excluded fields:

ignoringFields(String…fieldsToIgnore) - the assertion ignores the specified fields in the object under test
ignoringFieldsMatchingRegexes(String…regexes) - the assertion ignores the fields matching the specified regexes in the object under test
ignoringFieldsOfTypes(Class<?>…typesToIgnore) - the assertion ignores the object under test fields of the given types
ignoringPrimitiveFields() - avoid running the assertion on primitive fields