Testfinder MCP Server

testfinder

Running the whole test suite after every small edit is a slow loop. testfinder narrows it: give it one source file plus the project's file/import map — every file's path and the paths it imports — and it works out which tests are actually relevant to that file, why each one is relevant, and the exact command that runs just those tests:

• Direct importers — test files that import the source file themselves, at distance 1.
• Naming-convention matches — test files whose path is the source path with .test or .spec inserted before the final extension, either beside the source (src/foo.ts → src/foo.test.ts) or in the __tests__ form (src/__tests__/foo.test.ts). A source whose name has no extension gets the suffix appended instead (src/foo → src/foo.test).
• Transitive importers — test files that reach the source through other files, each at its shortest import distance, so a diamond in the graph resolves to the shorter route.

Every relevant test carries exactly one reason, decided by precedence: self (the source file is itself a test) over direct over convention over transitive. Results are ranked by that reason order, then by distance, then by path, and run_command is the npx tsx --test line that runs them in ranked order — or null when nothing is relevant. The result also reports total_files and test_files_considered, the count of test files in the set whether relevant or not. A file counts as a test when its name carries .test. / .spec. (or ends in .test / .spec), or when it lives under a test, tests, or __tests__ directory.

Imports that name paths outside the supplied set are external: they are ignored, never followed, and never an error. Duplicate import entries are de-duplicated and a file importing itself is ignored for graph purposes, though distances still flow through ordinary non-test files on the way to a test. Malformed input — a missing or unknown source_file, an empty file set, a duplicate file path, a wrongly typed field — is a validation error naming the offending path (for example files[1].imports[0] must be a string), and no partial result is produced. The computation is pure and local, and the tool only finds tests: running them, with the command it returns, is left to your own environment.

CLI

npx @reneturcios/testfinder find --input args.json
npx @reneturcios/testfinder --version

args.json contains the full arguments object:

{
  "source_file": "src/foo.ts",
  "files": [
    { "path": "src/foo.ts" },
    { "path": "src/bar.ts", "imports": ["src/foo.ts"] },
    { "path": "src/foo.test.ts" },
    { "path": "src/bar.test.ts", "imports": ["src/bar.ts", "react"] }
  ]
}

imports defaults to [] per file; here react is external to the set and ignored. src/foo.test.ts is a naming-convention match with no import of its own, and src/bar.test.ts reaches the source through src/bar.ts at distance 2. The result is printed as JSON:

{
  "source_file": "src/foo.ts",
  "relevant_tests": [
    { "path": "src/foo.test.ts", "reason": "convention", "distance": null },
    { "path": "src/bar.test.ts", "reason": "transitive", "distance": 2 }
  ],
  "total_files": 4,
  "test_files_considered": 2,
  "run_command": "npx tsx --test src/foo.test.ts src/bar.test.ts"
}

Exit codes: 0 on success, 1 on a runtime error (including an unreadable or invalid input file, or invalid input), 2 on a usage error.

MCP server

npx -y @reneturcios/testfinder mcp

MCP client config:

{
  "mcpServers": {
    "testfinder": {
      "command": "npx",
      "args": ["-y", "@reneturcios/testfinder", "mcp"]
    }
  }
}

Tools

• find_relevant_tests — Find the tests relevant to one source file from a file/import map.

  • source_file (string, required) — path of the source file; must be one of the supplied files
  • files (array, required, at least one) — files as {path, imports?} objects; path is unique across the set, and each imports entry either names another supplied file or anything else (external, ignored)

  Returns {source_file, relevant_tests, total_files, test_files_considered, run_command}, where each entry of relevant_tests is {path, reason, distance}.

Docker

docker run -i ghcr.io/cloudcorprecords/testfinder
docker run --rm -v "$PWD:/w" ghcr.io/cloudcorprecords/testfinder find --input /w/args.json

Development

npm install
npm run build   # tsc -> dist/
npm test        # tsx --test test/*.test.ts (pure local, no network)
npm run dev     # run the CLI from source

License

MIT — Copyright (c) 2026 Rene Turcios