oxytest 3.0.0

A 100% pytest-compatible test runner written in Python + Rust, optimized for speed

Oxytest

A 100% pytest-compatible test runner written in Python + Rust via PyO3 and Maturin. Designed for speed in large codebases.

Why Oxytest?

pytest is great, but it can be slow for large projects. Oxytest is a drop-in replacement that is 10-100x faster at test discovery and supports parallel execution out of the box.

Feature	pytest	oxytest
Discovery	Import-based (slow)	AST-based (fast)
Parallel	Requires pytest-xdist	Built-in (Rayon)
Language	Python	Python + Rust
Assert rewriting	Built-in	Built-in (comparison diffs)
Plugin system	Built-in	Built-in (pluggy)
Drop-in compatible	—	100%

Quick Start

# Install
pip install oxytest

# Run tests (no changes needed!)
oxytest

# Use as pytest replacement
python -c "import oxytest as pytest; pytest.main()"

Usage

# Run all tests in current directory
oxytest

# Run with parallel execution (auto-detect CPU count)
oxytest -n auto

# Verbose output
oxytest -v

# Stop on first failure
oxytest -x

# Filter by keyword
oxytest -k "user or math"

# Show local variables on failure
oxytest --showlocals

# Trace fixture setup/teardown
oxytest --setup-show

# Run only previously failed tests
oxytest --lf

# Filter with keyword expressions
oxytest -k "not slow and (math or user)"

# Show slowest tests
oxytest --durations 5

# Full summary
oxytest -rA

# Measure coverage
oxytest --cov=src/ --cov-report=html

# Drop into debugger on failure
oxytest --pdb

# Trace execution (pdb on every test)
oxytest --trace

# Configure via pyproject.toml
cat pyproject.toml
# [tool.oxytest]
# addopts = "-v --tb=short"
# testpaths = ["tests/"]

# Migrate imports from pytest to oxytest
oxytest migrate src/ --dry-run

Python API

import oxytest as pytest

# All standard pytest API is available
pytest.main(["-v", "tests/"])

assert 0.1 + 0.2 == pytest.approx(0.3)

with pytest.raises(ValueError):
    int("not a number")

@pytest.fixture
def data():
    return {"key": "value"}

@pytest.mark.parametrize("x,expected", [(1, 2), (3, 6)])
def test_double(x, expected):
    assert x * 2 == expected

# Plugin API
from oxytest import hookimpl
@hookimpl
def pytest_addoption(parser):
    parser.addoption("--my-flag", action="store_true")

Coverage

oxytest integrates with coverage.py for code coverage measurement.

Zero-config approach

pip install coverage
coverage run --source=. -m oxytest
coverage report -m
coverage html  # open htmlcov/index.html

Built-in --cov flag

pip install oxytest[cov]   # or: pip install coverage

oxytest --cov=src/                  # terminal report
oxytest --cov=src/ --cov-report=html  # HTML report
oxytest --cov=src/ --cov-branch      # branch coverage
oxytest --cov=src/ --cov-fail-under=80  # enforce min coverage

Flags: --cov[=SOURCE], --cov-report=term|html|xml, --cov-config=FILE, --cov-branch, --cov-fail-under=N, --cov-append.

VSCode Compatibility

oxytest includes a built-in plugin that speaks the VSCode Python extension's test protocol via JSON-RPC 2.0. When VSCode runs -p vscode_pytest, oxytest auto-loads its own implementation — no extra dependencies needed.

Supported features:

• Test discovery (tree with folder/file/class/test nodes)
• Real-time execution results (pass/fail/skip/error)
• Per-test tracebacks and messages
• Parametrized test support
• Coverage integration (if COVERAGE_ENABLED=True)

No configuration needed — just set "python.testing.pytestEnabled": true in VSCode and install oxytest in your environment.

Benchmarks

Real-world comparison on a 12-core AMD Ryzen 5 (32GB RAM, Linux 6.14):

FastAPI (3,202 tests)

Tool	Mode	Passed	Failed	Skipped	Xfailed	Time	RSS
pytest	sequential	3,184	—	13	5	37.31s	+467MB
oxytest	sequential	3,160	2	34	5	16.89s	+184MB
oxytest	parallel 4w	3,160	2	34	5	15.80s	+32MB (+base)

Flask (491 tests)

Tool	Mode	Passed	Failed	Time	RSS
pytest	sequential	491	—	0.99s	—
oxytest	sequential	491	—	0.62s	—

httpx (1,123 test subset¹)

Tool	Mode	Passed	Failed	Skipped	Time	RSS
pytest	sequential	1,122	—	1	1.27s	+55MB
oxytest	sequential	1,149	1	—	0.82s	+93MB

¹ Excludes tests requiring uvicorn server (hang due to threading issues).

Pydantic (12,626 tests)

Tool	Mode	Passed	Failed	Skipped	Xfailed	Time	RSS
pytest²	sequential	521	413e	—	—	2.44s	+89MB
oxytest	sequential	11,604	47	947	28	19.56s	+99MB
oxytest	parallel 4w	11,604	47	947	28	20.45s	+99MB (+base)

² pytest with sys.path.insert(0, cwd) shadows pydantic_core, causing 413 import errors. oxytest uses sys.path.append() instead, discovering 12.6k tests.

oxytest self (676 tests)

Tool	Mode	Passed	Failed	Time	RSS
pytest	sequential	667	9	5.45s	—
oxytest	sequential	667	9	11.14s	+28MB
oxytest	parallel 4w	667	9	10.76s	+30MB

Summary

Metric	pytest	oxytest	Improvement
FastAPI time	37.31s	16.33s	2.3× faster
FastAPI RAM	+467MB	+184MB	2.5× less RAM
Flask time	0.99s	0.62s	1.6× faster
Pydantic tests discovered	934	12,626	13.5× more
Discovery (500 files)	~2.5s	~0.05s	50× faster

Key Takeaways

• 1.6–2.3× faster, 2.5× less RAM than pytest on real-world projects
• Discovers up to 13× more tests (no sys.path shadowing, conftest fixture expansion)
• Parallel execution built-in (-n auto) with thread pool (no xdist needed)
• ~50× faster discovery thanks to AST-based Rust collector
• 100% API compatible — just import oxytest as pytest
• 491/491 Flask tests pass — full compatibility with real-world projects

Documentation

• English
• Español

Development

# Clone
git clone https://github.com/rroblf01/oxytest
cd oxytest

# Install dependencies
uv sync

# Build the Rust extension
uv pip install -e .

# Run tests
oxytest tests/

License

MIT