pytest-mergify

Find the pytest tests that pass and fail on the same code, and quarantine them so they stop failing your CI. Requires a Mergify account (set MERGIFY_TOKEN in CI); free for open source. Why tests go flaky in pytest, and how to fix them: mergify.com/learn/flaky-tests/pytest.

Pytest plugin for Mergify Test Engine.

More information at https://mergify.com

Features

• Test tracing — Sends OpenTelemetry traces for every test to Mergify's API
• Flaky test detection — Intelligently reruns tests to detect flakiness with budget constraints
• Test quarantine — Quarantines failing tests so they don't block CI
• Test selection — Runs first the tests a merge-queue bisection step failed in the step above, and stops as soon as one fails again

Installation

Install the package alongside pytest (>= 7.0):

pip install pytest-mergify

The plugin is auto-discovered by pytest — no manual registration required.

It ships as compiled wheels, with no source distribution, for CPython 3.10 or later on:

Elsewhere, and on glibc older than 2.28, no wheel of the release matches: pip installs an older release instead, or fails.

Configuration

Set the MERGIFY_TOKEN environment variable with your Mergify API token.

The plugin activates automatically when running in CI (detected via the CI environment variable). To enable outside CI, set MERGIFY_CI_ENABLE=true.

Environment Variables

The names these replace, PYTEST_MERGIFY_ENABLE and PYTEST_MERGIFY_DEBUG, are deprecated: they still work when the new name is not set, and the plugin says which one to switch to at the end of the session.

For detailed documentation, see the official guide.

Bisection steps: failures first

When Mergify's merge queue splits a failed batch, each bisection step only needs to tell whether it is red. The plugin asks Mergify whether the current run is such a step and, if so, runs first the tests this job failed in the run the step was split from (Fail First). They run before every other test; if one of them fails again, the step is red whatever the rest does, so the run stops there (exit code 1, the remaining tests not run) and the queue can split again without waiting for the suite. If they all pass, the rest of the suite runs as usual. No test is ever skipped, so a green step still comes from a full suite. A test a retry rescued, or a quarantined failure, does not stop the run.

It is on by default: there is nothing to configure, the plugin uses the token and job identity it already has, and Mergify decides. A job that must always run its suite in its usual order turns it off:

      - name: Run tests
        run: pytest
        env:
          MERGIFY_TOKEN: ${{ secrets.MERGIFY_TOKEN }}
          MERGIFY_FAIL_FIRST_ENABLE: "false"

Such a job never queries the endpoint; everything else the plugin does — test tracing, flaky detection, quarantine — is unaffected either way. Only a recognised no (false, no, off, 0) turns it off. MERGIFY_TEST_SELECTION_ENABLE, its former name, is still read while the new one is unset or empty, and the summary at the end of the run says to switch.

It only ever asks in a build of a merge-queue batch, the only builds a bisection step can be: on GitHub Actions, the event of the draft pull request the queue opened; on any other build, the queue's git note on the branch, one git ls-remote against origin that runs while the tests are being collected. Every other build asks nothing and sends nothing. Of a batch's builds, only those below a failed batch, and not retrying their own checks, ask: the others cannot be a bisection step, and send their results only when the batch holds two pull requests or more, so a bisection step may read them, or when they failed. A build where git cannot answer (no origin, credentials the test step does not hold) asks, as it would without this.

Every other situation — a run that is not a bisection step, an unreachable API, an answer from a newer Mergify this plugin does not understand — runs the full suite in its usual order. It is also enabled per organization on Mergify's side: until yours has it, every run is served the full suite, says nothing about it, and still sends its results, which show what Fail First would do there.

Under pytest-xdist this works with the load (the default with -n) and worksteal schedulers; with loadgroup, tests marked xdist_group still run before them. With loadscope and loadfile, xdist schedules whole modules or classes by size, so those tests do not run first: the run still stops once they have all run and one failed again. Workers on a remote gateway (--tx ssh=…) run to the end.

An opted-in job also tells Mergify what it concluded when its session ends — which tests failed, how many ran — in one small request sent before the test results are uploaded. That is what the next bisection step of the job is answered from, seconds after this one finished, without waiting for the results to be processed. If that request fails, the run's own result is untouched: the terminal says so, and the next step simply runs its full suite in its usual order.

Development

Prerequisites

• Python >= 3.10
• uv

Setup

uv sync

Running Tests

uv run poe test

uv run poe build builds the wheel into dist/; when one is there, poe test runs against it rather than the project's own install, which is how CI builds the extension once for every Python version. Every uv-driven build of the extension uses Cargo's dev profile.

Linting

uv run poe lint

License

Proprietary. Use is governed by the Mergify Terms of Service.