rtest 0.0.21

Python test runner built in Rust

rtest

A Python test runner built with Rust, currently supporting high-performance test-collection, with the goal of being a drop-in replacement for pytest.

⚠️ Development Status: This project is in early development (v0.0.x). Expect bugs, breaking changes, and evolving features as we work toward stability.

Performance

Benchmarks performed using hyperfine with 20 runs, 3 warmup runs per measurement, on an M4 Macbook Pro with 14 cores and 48GB RAM. More sophisticated benchmarks will be implemented in the future.

Against the flask Repository

hyperfine --command-name pytest --command-name rtest "pytest --collect-only" "rtest --collect-only" --warmup 3 --runs 20
Benchmark 1: pytest
  Time (mean ± σ):     229.9 ms ±   2.6 ms    [User: 184.5 ms, System: 37.4 ms]
  Range (min … max):   226.0 ms … 235.4 ms    20 runs
 
Benchmark 2: rtest
  Time (mean ± σ):      35.8 ms ±   1.2 ms    [User: 18.1 ms, System: 10.7 ms]
  Range (min … max):    34.2 ms …  40.3 ms    20 runs
 
Summary
  rtest ran
    6.41 ± 0.23 times faster than pytest

Against the httpx Repository

hyperfine --command-name pytest --command-name rtest "pytest --collect-only" "rtest --collect-only" --warmup 3 --runs 20
Benchmark 1: pytest
  Time (mean ± σ):     310.1 ms ±  18.6 ms    [User: 259.3 ms, System: 42.6 ms]
  Range (min … max):   291.0 ms … 344.4 ms    20 runs
 
Benchmark 2: rtest
  Time (mean ± σ):      20.6 ms ±   1.0 ms    [User: 12.5 ms, System: 5.5 ms]
  Range (min … max):    18.6 ms …  21.9 ms    20 runs
 
Summary
  rtest ran
   15.06 ± 1.15 times faster than pytest

Against the pydantic Repository

hyperfine --command-name pytest --command-name rtest "pytest --collect-only" "rtest --collect-only" --warmup 3 --runs 20
Benchmark 1: pytest
  Time (mean ± σ):      2.777 s ±  0.031 s    [User: 2.598 s, System: 0.147 s]
  Range (min … max):    2.731 s …  2.864 s    20 runs
 
Benchmark 2: rtest
  Time (mean ± σ):      61.2 ms ±   1.1 ms    [User: 40.1 ms, System: 14.4 ms]
  Range (min … max):    60.1 ms …  64.2 ms    20 runs
 
Summary
  rtest ran
   45.39 ± 0.95 times faster than pytest

Quick Start

Installation

pip install rtest

Requires Python 3.9+

Basic Usage

rtest --collect-only

Roadmap

Support executing tests, with parallelization built out of the box (bypassing pytest-xdist). Currently, this works for some cases, but is not yet stable.

Known Limitations

Parametrized Test Discovery

rtest currently discovers only the base function names for parametrized tests (created with @pytest.mark.parametrize), rather than expanding them into individual test items during collection. For example:

@pytest.mark.parametrize("value", [1, 2, 3])
def test_example(value):
    assert value > 0

pytest collection shows:

test_example[1]
test_example[2] 
test_example[3]

rtest collection shows:

test_example

However, when rtest executes tests using pytest as the executor, passing the base function name (test_example) to pytest results in identical behavior - pytest automatically runs all parametrized variants. This means test execution is functionally equivalent between the tools, but collection counts may differ.

Contributing

We welcome contributions! See Contributing Guide.

License

MIT - see LICENSE file for details.

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Acknowledgments

This project takes inspiration from Astral and leverages their excellent Rust crates:

• ruff_python_ast - Python AST utilities
• ruff_python_parser - Python parser implementation