If you need to develop your skills on Testing, look no further, I have created a course (only in portuguese at this time) that covers not only the usual JUnit, Mockito and AssertJ, but other frameworks as well, such as PITest, JQWik and ArchUnit.

Legacy code refactoring and Fitness functions are included too.

If you are not portuguese but you think the content is valuable to you, say something in the comments, I can start to consider to create an english version!

https://www.udemy.com/course/testes-ao-codigo-do-legacy-ao-archunit/?couponCode=PROMO-NOVIDADE