Is there a modern replacement for a mutation testing tool like Jester for Java?

Question

“Why just think your tests are good when you can know for sure? Sometimes Jester tells me my tests are airtight, but sometimes the changes it finds come as a bolt out of the blue. Highly recommended.” - Kent Beck

But I see that there is not even a tag called "Jester" in stackoverflow. So what is the modern replacement for Jester,if any ? How can one be sure that unit tests written are rock solid other than finding statistics from code coverage from tools like Cobertura and Clover?

Answer 1

As far as I'm aware mutation testing remains the best automated process for measuring the quality of your test suite. There are two good modern replacements for jester

http://pitest.org (I'm the author)

https://github.com/david-schuler/javalanche/

A detailed comparison between them, jester, and a couple of other systems is available here

http://pitest.org/java_mutation_testing_systems/

I think the main reason that jester never took off was that it was unworkably slow and scaled very badly.

PIT and javalanche both attempt to address this in a similar way. Instead of blindly running all the tests in a project against a mutation they first gather line coverage and run only those tests that can actually hit a mutation.

PIT also performs various other optimisations to speed things up and offers an option to re-use the results of previous analysis to greatly reduce the computational cost of subsequent runs.