Rtest: Python test runner built in Rust

0.0.46 · active · verified Sat Apr 11

Rtest is a high-performance Python test runner built in Rust. It replaces traditional import-heavy test collection with static Abstract Syntax Tree (AST) analysis, significantly speeding up test discovery, especially in large monorepos. Currently in early development (v0.0.x), it aims for `pytest` compatibility while offering performance gains and parallel test execution.

Warnings

breaking Rtest is in early development (v0.0.x); expect frequent bugs, breaking changes, and evolving features as it progresses towards stability.
Fix: Refer to the GitHub changelog for specific version updates and breaking changes. Pinning versions and testing upgrades is recommended.
gotcha Path Separator Differences: Rtest uses platform-specific path separators (e.g., `\` on Windows) in test nodeids, unlike `pytest` which normalizes to forward slashes (`/`). This can affect tools or scripts parsing test output.
Fix: Be aware of platform differences when parsing or comparing test nodeids in CI/CD pipelines or custom reporting tools.
gotcha Collection Failures on Complex Codebases: Projects with extensive use of `pytest` plugins, dynamic imports, or metaclass-heavy patterns may fail during rtest collection, even if they work with `pytest`.
Fix: If collection fails, try simplifying test module structure, reducing dynamic imports, or consider using `rtest --runner pytest` which leverages pytest for execution while still benefiting from rtest's collection.
gotcha `--runner native` Limitations: The native test runner is limited to simple test patterns (e.g., `unittest.TestCase`, plain assertions) and currently lacks full support for `pytest` fixtures or `conftest.py`.
Fix: For projects relying on `pytest` fixtures, use `rtest --runner pytest` to execute tests. Full fixture support for the native runner is under development.
gotcha Limited Parametrized Test Discovery: Rtest only expands parametrized tests during collection when decorator arguments can be statically resolved (e.g., literal values, module-level constants, enum members). Dynamic expressions may not be discovered.
Fix: Ensure parametrized arguments are statically resolvable for rtest to discover them. Refactor complex dynamic parameter generation if tests are not being collected.

Install

pip install rtest Install rtest

Imports

rtest command-line tool
```
rtest [options] [path...]
```
Rtest is primarily a command-line test runner. While it provides utility functions like `rtest.raises()`, the core interaction is via the `rtest` command.

Quickstart

Create a test file (e.g., `my_tests/test_example.py`) with standard Python test functions. Run `rtest` from your terminal, pointing it to your test directory or files. Rtest will discover and execute the tests.

# my_tests/test_example.py
def test_addition():
    assert 1 + 1 == 2

def test_failing_example():
    assert 'hello'.upper() == 'HELLO'

# To run these tests from your terminal:
# Navigate to your project root (e.g., one level above my_tests)
# $ pip install rtest
# $ rtest my_tests

# Example with a specific rtest utility:
# from rtest import raises
#
# def test_raises_exception():
#     with raises(ValueError, match='invalid literal'):
#         int('abc')

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