@jarroba/mcp-tests

@jarroba/mcp-tests

An MCP server that audits tests instead of writing them — and is meant to be pointed at your own work.

claude mcp add jarroba-tests npx -y @jarroba/mcp-tests

// Claude Desktop, Cursor, Cline, VS Code…
{ "mcpServers": { "jarroba-tests": { "command": "npx", "args": ["-y", "@jarroba/mcp-tests"] } } }

4 tools · ~1.2k tokens of context · stdio, runs on your machine · nothing is uploaded.

Why this exists

Told to "make the tests pass", an agent has two roads: diagnose the bug, or widen the matcher / drop the assertion / skip the case. The second is cheaper, it produces green, and it looks like work.

A better model does not fix that, and neither does asking nicely in the prompt — the incentive is structural. It needs a judge outside the model. That is what this is: the only part of the Jarroba Tools catalogue whose purpose is to disagree with whoever calls it.

The tools

test_audit	Case by case, what a test file actually asserts: which assert about a value, which only check that something exists, which assert nothing at all, and which are disabled — with the evidence for each verdict, so you can check the checker. TypeScript, JavaScript, Python, Java, Go.
test_diff_audit	Compares two versions of the same file and says whether the change strengthened or weakened the safety net: widened matchers (toBe → toContain → toBeGreaterThan), assertions that vanished, cases that stopped running. Run it on your own diff before claiming you are done.
test_cases	From a type to the cases worth writing — equivalence partitions and boundary values from a TypeScript signature or a JSON Schema — saying which technique applies and why. Boundary values mean nothing without an ordering, so a boolean and an enum do not get them. Includes a fast-check property test, and the five cases that matter most if you only have time for five (which never start with the typical value).
test_debt	Every disabled test with its age, from git blame. None of these appears in a coverage report, because as far as the runner is concerned they do not exist — it is the debt nobody measures and the one that lasts longest. Sorted oldest first, which is what makes it actionable.

Executes nothing. No test is run, no code is evaluated: it parses with tree-sitter.

It does not accuse lightly

A matcher it does not recognize comes back as "indeterminate", never as "asserts nothing". When in doubt it abstains, because a false accusation is how a tool like this gets switched off. If your team has a home-made expect(), declare it in dialects and it stops hedging.

Measured against a labelled corpus in five languages (TypeScript, JavaScript, Python, Java, Go): 21 accusations, 21 of them true, zero false positives, and zero cases the parser failed to delimit. That is the honest size of the measurement — 21 accusations, not a benchmark — and it is re-run on every change, so it is a floor rather than a claim.

Privacy

Transport is stdio: your MCP host launches this as a subprocess and talks over stdin/stdout. There is no endpoint, no account and no telemetry. npx downloads the package from npm the first time; after that nothing goes out.

test_audit and test_debt accept file paths and read whatever the process that launched them can read, so they are exactly as privileged as your MCP host. test_debt also shells out to git blame in the folder you point it at — that is where the age comes from, and it is the one thing a browser could never do.

More

Want everything (90 tools: logs by path, databases on a real ephemeral PostgreSQL, JTD diagrams, SPARQL, make simulation)? @jarroba/mcp. Just the logs? @jarroba/mcp-logs.

MIT — see LICENSE. Source: github.com/Invarato/JarrobaTools.

This package redistributes tree-sitter grammars (MIT, third-party); their notices are in dist/tree-sitter/NOTICE.txt.