bridle 0.3.0

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bridle

A harness for running pytest. It handles the collection and upload of test result information in a way that is resilient to crashes/OOMs in the code under test.

Features

• Crash resilience — pytest runs in a subprocess; events are flushed to disk after every test. A TestStarted event is written before each test runs, followed by a TestFinished event on completion. If the subprocess segfaults or OOMs mid-test, resolve_events() detects the unmatched TestStarted and synthesizes a failed TestFinished.
• Pluggable backends — can register one or more backends to upload test results to.
• Rich console output — summary table with outcome counts and duration, plus detailed failure panels, all printed to stderr.
• Custom Python interpreter — --python /path/to/python runs tests in a different Python environment (e.g. a uv venv or conda env). The target environment only needs pytest installed; bridle injects its own source via PYTHONPATH.
• Exit code passthrough — the harness returns the subprocess exit code so CI can gate on it.
• Per-test and total timeouts — --test-timeout-sec N kills the subprocess if any single test exceeds N seconds; --total-timeout-sec N kills it if the entire run exceeds N seconds. Timed-out tests appear as normal failures with a timeout-specific message in longrepr.

JSONL Schema

The JSONL file contains a tagged union of two event types, discriminated by the type field:

TestStarted — emitted before each test runs

{"type":"test_started","nodeid":"tests/test_a.py::test_ok","start":1735689600.0,"location":["tests/test_a.py",0,"test_ok"]}

Field	Type	Description
type	"test_started"	Event discriminator
nodeid	string	Pytest node ID
start	float	Epoch timestamp when the test starts
location	[string, int|null, string]	[filepath, lineno, domain], or null

TestFinished — emitted when a test phase completes

{"type":"test_finished","nodeid":"tests/test_a.py::test_ok","outcome":"passed","when":"call","duration":0.005,"start":1735689600.0,"stop":1735689600.005,"location":["tests/test_a.py",0,"test_ok"],"longrepr":null,"sections":null,"wasxfail":null}

Field	Type	Description
type	"test_finished"	Event discriminator
nodeid	string	Pytest node ID
outcome	string	passed, failed, skipped, error, xfailed, xpassed
when	string	Phase: setup, call, or teardown
duration	float	Test duration in seconds
start	float	Epoch timestamp when the phase started
stop	float	Epoch timestamp when the phase ended
location	[string, int|null, string]	[filepath, lineno, domain], or null
longrepr	string | null	Failure representation, null on pass
sections	[[string, string]] | null	Captured output sections, e.g. [["Captured stdout call", "..."]]
wasxfail	string | null	xfail reason if the test was marked xfail

TestEvent = TestStarted | TestFinished is a discriminated union. Use resolve_events() to match pairs — unmatched TestStarted events become synthetic failed TestFinished entries.

Timeouts

Kill tests that hang or entire runs that take too long:

# Kill any single test that runs longer than 30 seconds
uv run bridle tests/ --test-timeout-sec 30

# Kill the entire run if it exceeds 2 minutes
uv run bridle tests/ --total-timeout-sec 120

# Both can be combined
uv run bridle tests/ --test-timeout-sec 30 --total-timeout-sec 120

When a timeout fires, the subprocess is killed and TestFinished events are written for all active tests with a timeout-specific longrepr. Downstream code (display, backends) sees them as normal failed tests.

Custom Python Interpreter

Use --python to run tests in a different Python environment while bridle orchestrates from the current one:

# Run tests using a uv venv
uv run bridle tests/ --python .venv/bin/python

# Run tests using a conda environment
uv run bridle tests/ --python /path/to/conda/env/bin/python

The target environment only needs pytest installed. bridle automatically injects its own source into PYTHONPATH so the subprocess can find the bridle plugin without installing bridle into the target env.

Buildkite Test Analytics

The buildkite backend uploads test results to Buildkite Test Analytics for flaky test detection, suite analytics, and performance tracking.

Setup

Set the BUILDKITE_ANALYTICS_TOKEN environment variable to your Buildkite Test Analytics suite API token:

export BUILDKITE_ANALYTICS_TOKEN="your-suite-token"
uv run bridle tests/ --backend buildkite

Environment Variables

Variable	Required	Description
BUILDKITE_ANALYTICS_TOKEN	Yes	Suite API token for authentication
BUILDKITE_ANALYTICS_API_URL	No	Custom API endpoint (defaults to https://analytics-api.buildkite.com/v1/uploads)

The backend automatically detects CI environment (Buildkite, GitHub Actions, CircleCI) from standard CI env vars. If no CI provider is detected, it falls back to a generic environment.

Behavior

• Upload is best-effort: HTTP/network errors are logged as warnings, never propagated.
• If BUILDKITE_ANALYTICS_TOKEN is not set, a warning is logged and upload is skipped.
• Test results are uploaded in batches of 100.
• Crash events (unmatched TestStarted) are reported as failed tests.

Adding a Backend

Subclass Backend and register it in backends/__init__.py:

from bridle.backends._base import Backend
from bridle._schema import TestEvent

class MyBackend(Backend):
    def name(self) -> str:
        return "my-backend"

    def upload(self, events: list[TestEvent]) -> None:
        # upload logic here
        ...

Then add it to the registry in backends/__init__.py:

_REGISTRY: dict[str, type[Backend]] = {
    "stub": StubBackend,
    "my-backend": MyBackend,
}

Development

# Install dev dependencies
uv sync

# Run tests
uv run pytest tests/

# Update syrupy snapshots
uv run pytest tests/ --snapshot-update

Project Structure

src/bridle/
├── __init__.py          # main() entrypoint
├── __main__.py          # python -m support
├── _schema.py           # TestStarted/TestFinished pydantic models + Outcome enum + JSONL ser/de
├── _monitor.py          # Subprocess monitor with per-test and total timeout enforcement
├── _plugin.py           # TestResultPlugin (pytest plugin, flush-per-line)
├── _runner.py           # Subprocess entry point
├── _harness.py          # Orchestrator: argparse, subprocess, read results, dispatch
├── _console.py          # Rich-formatted output helpers
└── backends/
    ├── __init__.py      # Registry + get_backend()
    ├── _base.py         # Abstract Backend base class
    ├── _buildkite.py    # BuildkiteBackend (Buildkite Test Analytics)
    └── _stub.py         # StubBackend (logs to console)