rpytest

Run your pytest suite faster. Change nothing.

rpytest is a Rust-powered, drop-in replacement for pytest that eliminates startup and collection overhead while keeping your existing tests, fixtures, and plugins completely untouched.

# Install and run - that's it
pip install rpytest
rpytest

Why rpytest?

The speed comes from a persistent daemon that keeps Python warm between runs. No more paying interpreter startup costs on every invocation.

Installation

# Via pip (recommended)
pip install rpytest

# Via cargo
cargo install rpytest

# From source
git clone https://github.com/neul-labs/rpytest.git
cd rpytest && cargo install --path crates/rpytest

Usage

rpytest mirrors pytest's CLI exactly. If you know pytest, you know rpytest.

# Run all tests
rpytest

# Run specific tests
rpytest tests/test_api.py::test_login

# Filter by keyword or marker
rpytest -k "auth" -m "not slow"

# Parallel execution (pytest-xdist compatible, no plugin needed)
rpytest -n auto

# Watch mode for TDD
rpytest --watch

# Verify identical behavior to pytest
rpytest --verify-dropin

Key Features

Instant Startup

The first run spawns a background daemon. Every subsequent run is a fast RPC call—no interpreter startup, no re-importing your test modules.

Full pytest Compatibility

• All pytest CLI flags work identically
• Your plugins, fixtures, and conftest.py files run unchanged
• pytest.ini, pyproject.toml, and tox.ini configs are respected
• Exit codes and JUnit XML match pytest exactly

Built-in Parallelism

rpytest -n 4  # Run on 4 workers
rpytest -n auto  # Auto-detect based on CPU cores

No pytest-xdist required. Duration-aware load balancing included.

Watch Mode

rpytest --watch

File changes trigger automatic re-runs of affected tests.

Flakiness Detection

rpytest --reruns 3  # Auto-retry failed tests
rpytest --flaky-report  # See which tests are flaky

Sharding for CI

rpytest --shard 0 --total-shards 4  # Perfect for parallel CI jobs

How It Works

1. First run: Spawns a Python daemon that collects your test suite once
2. Subsequent runs: Rust CLI filters tests and dispatches to warm Python workers
3. Results stream back in real-time for instant feedback

The daemon persists between runs, so repeated invocations (TDD loops, CI retries, --last-failed) skip all the startup work.

Daemon Management

rpytest --daemon-status  # Check health
rpytest --daemon-stop    # Stop the daemon
rpytest --cleanup        # Clean stale contexts

Drop-in Guarantee

Run the verification harness to confirm identical behavior:

rpytest --verify-dropin

This runs both pytest and rpytest on your suite and compares collection counts, pass/fail results, and exit codes.

Configuration

rpytest reads your existing pytest configuration—no new config files needed:

• pytest.ini
• pyproject.toml ([tool.pytest.ini_options])
• tox.ini
• setup.cfg

Documentation

Full documentation at docs.neullabs.com/rpytest

Contributing

Contributions welcome! See CONTRIBUTING.md for guidelines.

git clone https://github.com/neul-labs/rpytest.git
cd rpytest
cargo build
cargo test

License

Licensed under either of Apache License, Version 2.0 or MIT License at your option.