Is mutation testing useful in practice?

Question

Do you have any examples of real life applications of mutation testing? Does it work better than simple test coverage tools? Or is it useless?

What are the advantage

Answer 1

I known that this is a old question but recently Uncle Bob write a blog post very interesting about mutating testing that can help understand the usefully of this type of testing:

Uncle Bob mutating testing blog post

Answer 2

Mutation testing has helped me identify problems with test case assertions.

For example, when you get a report that says "no mutant has been killed by test case x", you take a look, and it turns out the assertion had been commented out.

According to this paper, developers at Google use Mutation testing as a complement to code-review and pull-request inspections. They seem happy about the results:

Developers have decided to redesign large chunks of code to make them testable just so a mutant could be killed, they have found bugs in complex logical expressions looking at mutants, they have decided to remove code with an equivalent mutant because they deemed it a premature optimization, they’ve claimed the mutant saved them hours of debugging and even production outages because no test cases were covering the logic under mutation properly. Mutation testing has been called one of the best improvements in the code review verification in years. While this feedback is hardly quantifiable, combined with the sheer number of thousands of developers willing to inspect surfaced mutants on their code changes makes a statement.