Mutation Testing with Stryker

Run mutation testing to verify your test suite actually catches bugs.

For .NET (Stryker.NET)

dotnet tool install -g dotnet-stryker
cd src/backend/Tests/MatchingServiceTests
dotnet stryker

Configure stryker-config.json:

{
  "stryker-config": {
    "project": "CandidateMatchingEngine.csproj",
    "mutate": ["**/Services/**/*.cs", "!**/Generated/**"],
    "thresholds": { "high": 80, "low": 60, "break": 40 },
    "reporters": ["html", "json", "progress"],
    "concurrency": 4
  }
}

For TypeScript/JavaScript (StrykerJS)

npx stryker init
npx stryker run

Interpreting Results

• Killed: Test caught the mutation (GOOD)
• Survived: Tests missed the change (BAD -- add tests)
• Mutation score = killed / (killed + survived) -- target >60%

CI Integration

- script: dotnet stryker --threshold-break 40
  displayName: "Mutation Testing"
  condition: eq(variables['Build.Reason'], 'PullRequest')

Arguments

• --project=<path>: Path to test project
• --threshold=<n>: Break build if score below this (default: 60)