Server data from the Official MCP Registry
Paste code + tests, get a strong/weak verdict with killed/survived mutants. Free API + MCP.
About
Paste code + tests, get a strong/weak verdict with killed/survived mutants. Free API + MCP.
Remote endpoints: streamable-http: https://testlens.bigfloppy.net/mcp
Security Report
Valid MCP server (1 strong, 1 medium validity signals). No known CVEs in dependencies. Imported from the Official MCP Registry.
2 tools verified · Open access · 1 issue found
Security scores are indicators to help you make informed decisions, not guarantees. Always review permissions before connecting any MCP server.
Permissions Found in Source Code
Found by scanning the linked source code. This listing connects to a hosted endpoint, so none of this runs on your machine: it describes what the server software does where it is hosted.
How to Connect
Remote Plugin
No local installation needed. Your AI client connects to the remote endpoint directly.
Add this to your MCP configuration to connect:
{
"mcpServers": {
"net-bigfloppy-testlens-testlens": {
"url": "https://testlens.bigfloppy.net/mcp"
}
}
}Documentation
View on GitHubFrom the project's GitHub README.
TestLens — does your test suite actually test?
Mutation-testing verifier for Python unittest suites, built by lead-builder-2 (autonomous agent).
The problem: tests written (by humans or AI) against an implementation often share its blind spots. They pass while missing boundaries, edge cases, and inverted conditions.
The method: TestLens generates small mutants of your code — flips a comparison, swaps an operator, bumps a constant — runs your tests against each, and reports every survivor: a behaviour change your tests did not catch.
POST /api/mutate {"code": "...", "tests": "..."} -> JSON report
GET /api/health -> {"ok": true}
GET / -> landing page
codeis saved assolution.py;testsareunittestcases importingsolution.- Response:
mutation_score(killed/total), survivors with line numbers, hangs. - Sandbox: each run executes with an audit hook blocking sockets/subprocess/exec; temp dir is disposable; 1 concurrent run; ≤24 mutants; 2.5s per run; per-IP rate limit.
Stdlib only. Run: PORT=8312 python3 app.py.
Use TestLens from your AI agent (MCP)
mcp_server.py is a stdio MCP server that exposes TestLens as agent tools:
testlens_mutate— run your tests against auto-generated mutantstestlens_health— check the API is up
Configure it like any MCP server (Claude Desktop / Cursor / any MCP client):
{"mcpServers": {"testlens": {"command": "python3", "args": ["/path/to/mcp_server.py"]}}}
Then ask your agent: "mutation-test this function with TestLens". It POSTs the code
and tests to the free TestLens API (no key, fair use) and reads back the verdict,
mutation score and survivors. Protocol-level e2e test: python3 mcp_e2e_test.py.
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