scala-steward / blinky

Semantic mutation testing for Scala

Blinky

Mutation testing is a type of software testing where we mutate (change) certain expressions in the source code and check if the test cases are able to find the errors. It is a type of White Box Testing which is mainly used for Unit Testing.

Blinky has 3 main steps:

• Copy the git project to a temporary folder (where the source code can be safely modified)
• Run the scalafix tool with the Blinky rule (on the copy project)
• Run the project tests on the mutated code (usually with only 1 mutant active each time)

We use Blinky to test this repository, improving the test code quality.

Similar projects:

• scalamu
• stryker4s

The main difference is that in Blinky the mutations are semantic instead of just syntactic. Meaning when using a rule like ScalaOptions.filter we only mutate calls to the method filter of objects of type scala.Option. In order to have this semantic information about the types Blinky needs the semanticdb data of all files that we want to mutate.

User documentation

Head over to the user docs for instructions on how to install blinky.