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mutation-testing-metrics
Advanced tools
Mutation testing metrics
Utility function to calculate mutation testing metrics..
See mutant states and metrics on the Stryker website for more details about mutation testing metrics.
Usage example
See the below example (uses TypeScript):
import { MetricsResult, calculateMutationTestMetrics } from 'mutation-testing-metrics';
import { MutationTestResult } from 'mutation-testing-report-schema';
const mutationTestReport: MutationTestResult = {
/*... Get a holds of mutation test results somehow */
};
const result: MetricsResult = calculateMutationTestMetrics(mutationTestReport);
console.log('Mutation score', result.metrics.mutationScore);
API Reference
calculateMutationTestMetrics [(MutationTestResult) => MutationTestMetricsResult]
Calculates the full mutation test metrics from both the files-under-test as well as (optionally) the test files.
The input is a mutation test result valid according to the [https://github.com/stryker-mutator/mutation-testing-elements/tree/master/packages/report-schema#readme]
Returns A MutationTestMetricsResult that contains both the systemUnderTestMetrics as well as the testMetrics
calculateMetrics [(MutationTestResult) => MetricsResult]
Calculates the files-under-test metrics inside of a mutation testing report.
The input is a mutation test result valid according to the [https://github.com/stryker-mutator/mutation-testing-elements/tree/master/packages/report-schema#readme]
aggregateResultsByModule [(Record<string, MutationTestResult>) => MutationTestResult]
Aggregates multiple reports together into a single report, grouped by module.
Input: resultsByModule The MutationTestResult objects by module name.
Types
Types are included and documented with TypeScript.
Use case: merging multiple JSON reports
You can use this script to merge multiple JSON reports together.
const { aggregateResultsByModule } = require('mutation-testing-metrics');
const fs = require('fs');
const packagesRoot = './packages';
const reportsPerModule = fs
.readdirSync(packagesRoot)
.map((pkg) => [pkg, `${packagesRoot}/${pkg}/reports/mutation/mutation.json`])
.filter(([, report]) => fs.existsSync(report))
.map(([pkg, report]) => [pkg, require(report)])
.reduce((acc, [pkg, report]) => {
acc[pkg] = report;
return acc;
}, {});
const monoReport = aggregateResultsByModule(reportsPerModule);
fs.writeFileSync('./mono-report.html', reportTemplate(monoReport), 'utf-8');
function reportTemplate(report) {
const scriptContent = fs.readFileSync(require.resolve('mutation-testing-elements/dist/mutation-test-elements.js'), 'utf-8');
return `<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<script>
${scriptContent}
</script>
</head>
<body>
<mutation-test-report-app>
Your browser doesn't support <a href="https://caniuse.com/#search=custom%20elements">custom elements</a>.
Please use a latest version of an evergreen browser (Firefox, Chrome, Safari, Opera, Edge, etc).
</mutation-test-report-app>
<script>
const app = document.querySelector('mutation-test-report-app');
app.report = ${escapeHtmlTags(JSON.stringify(report))};
function updateTheme() {
document.body.style.backgroundColor = app.theme === 'dark' ? '#222' : '#fff';
}
app.addEventListener('theme-changed', updateTheme);
updateTheme();
</script>
</body>
</html>`;
}
function escapeHtmlTags(json) {
return json.replace(/</g, '<" + "');
}
FAQs
Utility functions to calculate mutation testing metrics.
The npm package mutation-testing-metrics receives a total of 1,512,082 weekly downloads. As such, mutation-testing-metrics popularity was classified as popular.
We found that mutation-testing-metrics demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 2 open source maintainers collaborating on the project.
Package last updated on 13 Feb 2026
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