net.bigfloppy.testlensPublished by testlens.bigfloppy.netOfficial publisherv1.1.0Updated Oct 25, 2026
Paste code + tests, get a strong/weak verdict with killed/survived mutants. Free API + MCP.
TestLens's hosted MCP server (testlens.bigfloppy.net), published by testlens.bigfloppy.net; no sign-in required; Streamable HTTP; 2 tools.
No AI overview yet: these facts come from the registry entry and the server itself.
Web executable via Streamable HTTP. Remote servers run from the web runtime once configured in a workspace.
Paste this prompt into Claude Code, Codex, Cursor or another agent — or into SourceWeft chat. The agent reads this server's install guide, shows you its publisher, endpoint and sign-in, and adds it to your client once you agree. Keys never go into a command.
Read https://sourceweft.com/mcp/net.bigfloppy.testlens%2Ftestlens/install.md and connect the MCP server it describes to my client. Before changing any config, show me its publisher, endpoint and sign-in method and wait for my OK. Never put an API key in a command or in a file I would commit; ask me where it should come from.Add this to your client's mcpServers config.
{
"mcpServers": {
"testlens": {
"type": "http",
"url": "https://testlens.bigfloppy.net/mcp"
}
}
}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.
code is saved as solution.py; tests are unittest cases importing solution.mutation_score (killed/total), survivors with line numbers, hangs.Stdlib only. Run: PORT=8312 python3 app.py.
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 upConfigure it like any MCP server (Claude Desktop / Cursor / any MCP client):
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.
Source: README.md at commit 6f8779a
Mutation-test Python code: submit the module code and unittest test cases; TestLens generates small mutants (flipped comparisons, swapped operators, inverted booleans), runs the tests against each and reports the mutation score plus every SURVIVOR - behaviour the tests do not check. Free, no key.
coderequiredtestsrequiredCheck the TestLens API is up. Takes no arguments.
Takes no parameters.
90% of the applicable checks met
How complete this listing is, computed from the registry entry, the endpoint and public sources. Not a rating of the server and not a statement that it is safe or working today: reachability is a dated check, and no installs or reviews go into the score.
Declare a license in the repository or the registry entry.
POST /api/mutate {"code": "...", "tests": "..."} -> JSON reportGET /api/health -> {"ok": true}GET / -> landing page{"mcpServers": {"testlens": {"command": "python3", "args": ["/path/to/mcp_server.py"]}}}