mutation-testing-js

Mutation testing reveals weak JavaScript tests by systematically introducing small code changes, called mutants, to evaluate if your test suite catches them. If a mutant survives, your tests have gaps in logic or coverage that need improvement.

You can run mutation testing on TypeScript projects by installing the Stryker toolkit and executing the command `npx stryker run` against your source files. This process applies operator mutations and branch analysis to evaluate test effectiveness.

Yes, mutation testing requires Node.js and the Stryker toolkit to run against your source files. The analysis typically excludes test files to focus mutation operators on your actual JavaScript and TypeScript code changes.

Mutation testing results like Killed, Survived, and No Coverage indicate whether your tests effectively caught bugs. Killed mutants mean tests passed, Survived indicates weak tests, and No Coverage shows missing test paths to guide actionable improvements.

Mutation testing applies systematic mutation operators such as arithmetic, conditional, and logical mutations to JavaScript code. These operators introduce small changes to evaluate whether your test suite catches the altered logic across code changes.