testland/stryker-net-mutation
Use for any question about mutation testing in .NET or C#, or when a .NET suite passes with good coverage but may assert nothing: sets up Stryker.NET (dotnet-stryker tool, project and solution scoping, xUnit, NUnit or MSTest, stryker-config.json thresholds) and runs it in CI. Has a worked example and mutator levels.
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stryker-net-mutators.mdreferences/
Stryker.NET mutators and configuration reference
Full mutator set and configuration options for stryker-net-mutation. Linked
inline from that skill's SKILL.md, which keeps the conditional-boundary example
in the spine.
Mutators at the Standard level
A surviving mutant means the test suite doesn't distinguish the original behavior from the mutated one. Common mutators:
| Mutator | Example |
|---|---|
| Arithmetic operator | + → -, * → / |
| Conditional boundary | < → <=, > → >= |
| Conditional negation | !x → x |
| Logical operator | && → || |
| Equality | == → != |
| Return value | return foo() → return null / return "" / return 0 |
| Statement removal | Foo(); → ; |
| String literal | "x" → "" |
mutation-level controls how many of these run:
Basic(fewest mutators)Standard(default, recommended)AdvancedComplete(most mutators; slowest)
Configuration options
Per stryker-net-config, every option nests under a single stryker-config
root object; Stryker.NET publishes no JSON schema, so there is no $schema key.
Core keys: project, test-projects, mutation-level, thresholds (high /
low / break), concurrency, reporters. Command-line flags mirror them, for
example --solution (multi-project discovery), --project, --mutate (scope /
exclude files), and --break-at <baseline> for the CI gate.