Test MCP servers in plain language.
MCP Rigor is an open-source, deterministic, black-box test framework for Model Context Protocol servers — built for QA teams, developers, and product owners.
An open-source project proudly funded by LoopIQ.
Test: "An active customer can be found"
Call tool "find_customer" with:
customerId: "C-100"
Expect "structuredContent.status" equals "active"No test code. No AI interpretation. The same sentence always compiles into the same test.
🧪 For QA
Write tests that read like acceptance criteria, use the guided no-code wizard, or edit and run suites in a local browser workspace.
👩💻 For developers
Contract locks with SHA-256 fingerprints, classified drift reports, sanitized traces, semantic snapshots, and stable error codes.
📋 For product owners
Readable tests double as living acceptance criteria, and evidence bundles prove what was tested, against which server, and when.
🔀 Transport parity
Run the same scenario against a local stdio server and a deployed Streamable HTTP endpoint and see exactly where behavior differs.
📊 Data-driven
Tables, CSV, JSON, YAML, Excel, REST, and Google Sheets — with typed columns, filters, joins, and seeded sampling.
🛡️ Safe by default
Remote data and custom code are opt-in. Reports are sanitized and secrets are redacted centrally.
Install and run in one minute
npm install --save-dev mcprigor
npx mcprigor init tests/acceptance.mcpr
npx mcprigor check tests/acceptance.mcpr
npx mcprigor test tests/acceptance.mcpr --html report.htmlTests use the .mcpr extension and compile to the same runtime model as YAML.
Backed by LoopIQ
MCP Rigor is funded and supported by LoopIQ, the AI-Native governance platform for software releases. LoopIQ connects requirements to runnable tests; MCP Rigor executes them deterministically with auditable evidence — one thread from requirement → test → execution → proof.
Frequently asked questions
What is MCP Rigor?
MCP Rigor is an open-source, deterministic, black-box test framework for Model Context Protocol (MCP) servers. QA teams write tests in plain language (.mcpr files); developers get contract locks, drift detection, evidence bundles, and transport parity. It is funded by LoopIQ.
How do I test an MCP server?
Install with npm install --save-dev mcprigor, create a test with npx mcprigor init tests/acceptance.mcpr, validate it with npx mcprigor check, and run it with npx mcprigor test. Tests call tools, read resources, and get prompts, then assert on response fields.
Does MCP Rigor use AI to interpret tests?
No. The plain-language wording compiles deterministically — the same sentence always produces the same test. No AI model interprets the wording, which keeps runs repeatable in CI.
What transports does MCP Rigor support?
Local stdio subprocesses and deployed Streamable HTTP servers. Transport parity mode runs the same scenario against both and reports semantic differences.
What is the .mcpr file extension?
MCP Rigor plain-language tests use the .mcpr extension — short for MCP Rigor. A .mcpr file contains readable test scenarios that compile deterministically to the same runtime model as YAML.
Is MCP Rigor free?
Yes. MCP Rigor is open source under the Apache-2.0 license, funded and supported by LoopIQ, the AI-Native governance platform for software releases.
Who is MCP Rigor for?
QA engineers who want plain-language MCP tests, developers who need contract drift detection and debugging evidence, and product owners who want readable acceptance criteria with auditable proof.