stryker-mutation

Overview

Mutation testing plants small bugs (mutants) in production code and re-runs the tests. A mutant that survives means no test noticed the change: the line is covered but not checked. StrykerJS does this for JavaScript and TypeScript, including React, Angular, Vue, Svelte and Node projects ([introduction][si]).

When to use

• A JS/TS suite has ≥80% line or branch coverage and the team wants to know whether its assertions catch bugs.
• Reviews keep finding weak assertions (toBeTruthy() on objects); the mutation score makes the cost visible.
• A critical module needs a stronger bar than coverage.

Step 1 - Install the core and one runner