rtest 0.0.35

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.

Test Class Inheritance Collection

When a test class inherits from another test class, rtest collects inherited test methods differently than pytest. While pytest shows inherited methods under each subclass that inherits them, rtest currently shows inherited methods only under the base class where they are defined. For example:

# test_example.py
class TestAddNumbers:
    def test_add_positive_numbers(self):
        pass
    
    def test_add_negative_numbers(self):
        pass

# test_floating_numbers.py  
from tests.test_example import TestAddNumbers

class TestAddFloatingNumbers(TestAddNumbers):
    def test_add_simple_floats(self):
        pass

pytest collection shows:

test_example.py::TestAddNumbers::test_add_positive_numbers
test_example.py::TestAddNumbers::test_add_negative_numbers
test_floating_numbers.py::TestAddNumbers::test_add_positive_numbers
test_floating_numbers.py::TestAddNumbers::test_add_negative_numbers
test_floating_numbers.py::TestAddFloatingNumbers::test_add_positive_numbers
test_floating_numbers.py::TestAddFloatingNumbers::test_add_negative_numbers
test_floating_numbers.py::TestAddFloatingNumbers::test_add_simple_floats

rtest collection shows:

test_example.py::TestAddNumbers::test_add_positive_numbers
test_example.py::TestAddNumbers::test_add_negative_numbers
test_floating_numbers.py::TestAddFloatingNumbers::test_add_positive_numbers
test_floating_numbers.py::TestAddFloatingNumbers::test_add_negative_numbers
test_floating_numbers.py::TestAddFloatingNumbers::test_add_simple_floats

We believe this difference is desirable, in that TestAddNumbers isn't collected twice from different modules.

Path Separator Handling

rtest uses platform-specific path separators in test nodeids, while pytest normalizes all paths to use forward slashes (/) regardless of platform. For example:

On Windows:

• pytest shows: tests/unit/test_example.py::test_function
• rtest shows: tests\unit\test_example.py::test_function

On Unix/macOS:

• Both show: tests/unit/test_example.py::test_function

This difference is intentional as rtest preserves the native path format of the operating system.

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 crates from [ruff].