Metadata-Version: 2.4
Name: pytest-portion
Version: 0.3.0
Summary: Select a portion of the collected tests
Project-URL: homepage, https://github.com/mgaitan/pytest-portion
Author-email: Martín Gaitán <gaitan@gmail.com>
License: BSD-3-Clause
License-File: LICENSE
Keywords: pytest,testing
Classifier: Development Status :: 4 - Beta
Classifier: Framework :: Pytest
Classifier: Intended Audience :: Developers
Classifier: License :: OSI Approved :: BSD License
Classifier: Operating System :: OS Independent
Classifier: Programming Language :: Python
Classifier: Programming Language :: Python :: 3
Classifier: Programming Language :: Python :: 3 :: Only
Classifier: Programming Language :: Python :: 3.10
Classifier: Programming Language :: Python :: 3.11
Classifier: Programming Language :: Python :: 3.12
Classifier: Programming Language :: Python :: 3.13
Classifier: Programming Language :: Python :: 3.14
Classifier: Programming Language :: Python :: Implementation :: CPython
Classifier: Programming Language :: Python :: Implementation :: PyPy
Classifier: Topic :: Software Development :: Testing
Requires-Python: >=3.10
Requires-Dist: pytest>=3.5.0
Description-Content-Type: text/markdown

# pytest-portion

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Select a portion of the collected tests, so you can run different parts of your test suite
in different instances to scale horizontally.

## Use case

Suppose you have a big, slow test suite, but you can trigger several CI workers
to run different portions of it, in a sake lazy/simple way to parallelize it.

A basic, obvious way to do that is to explictily
collect from different directories/modules:

- worker1: `pytest tests/a` (100 tests, ~4 minutes to finish)
- worker2: `pytest tests/b` (20 tests, ~1 minute to finish)
- worker3: `pytest tests/c tests/d` (30 tests, ~1 minute to finish)

The problem is that directory `tests/a` may have a lot more tests that `tests/c` plus `test/d`,
so `worker1` takes a lot more to finish.

With `pytest-portion` you can still split the tests in different instances, but letting
the extension makes the selection in a more balanced way.

- worker1: `pytest --portion 1/3 tests` (first 50 tests, ~2 minutes)
- worker2: `pytest --portion 2/3 tests` (next 50 tests, ~2 minutes)
- worker3: `pytest --portion 3/3 tests` (last 50 tests, ~2 minutes)

In this case, the tests of all the directories are collected, but only a third (a different one!) of them will
be actually executed on each worker.

Note this balance is **by number of tests**, so if there is very slow tests in a particular portion,
the duration may not be expected.

For a fine tuning, you could pass the portion in a more explicit way:

- worker1: `pytest --portion 0:0.5 tests` (first half, 1st to 75th test)
- worker2: `pytest --portion 0.5:0.8 tests` (next 30%, from 76th to 125th)
- worker3: `pytest --portion 0.8:1 tests` (last 20%)

## Installation

You can add "pytest-portion" to your project from [PyPI](https://pypi.org/project/pytest-portion/) with [uv](https://docs.astral.sh/uv/).

```bash
uv add --dev pytetest-portion
```

Or via [pip]

```bash
pip install pytest-portion
```

## Usage

There are three modes of operation: **Test-level** (default), **File-level**, and **Function-level**.

### 1. Test-level Slicing (Default)

Pytest collects all tests first, then `pytest-portion` filters them.

Pass `--portion <i/n>` where:

- `n` is the total number of portions.
- `i` is the i-th portion to select (`1 <= i <= n`).

> **Note:**
> If the number of tests collected is not divisible by `n`, the last portion will contain the rest.
> For instance, if you have `test_1`, `test_2` and `test_3`, `--portion 1/2` will run the first one,
> and `--portion 2/2` the last 2.

Alternatively, use `--portion start:end` where `start` and `end` are coefficients between 0 and 1.

### 2. File-level Slicing

For very large projects, collection itself can be slow. Use `--portion-files` to slice the list of
discovered files **before** pytest starts collecting tests from within them. This can significantly
reduce collection time in large repositories.

```bash
# Collect and run only the files belonging to the first half of the suite
pytest --portion 1/2 --portion-files tests/
```

### 3. Function-level Slicing

With multiple parametrized test functions (e.g. `test_compare1[...]`, `test_compare2[...]`), the default splits the **entire** collected list. That can put all of one function in portion 1 and all of another in portion 2, so workers get uneven loads.

Use `--portion-functions` to split **within each test function** instead: each function’s cases are portioned separately, so every function contributes proportionally to the selected set.

```bash
# Half from test_compare1 and half from test_compare2
pytest --portion 1/2 --portion-functions tests/
```

> **Note:** `--portion-files` and `--portion-functions` cannot be used together.

## Contributing

Contributions are very welcome. Please ensure the coverage at least stays
the same before you submit a pull request.

## License

Distributed under the terms of the [BSD-3] license, "pytest-portion" is free and open source software.

## Issues

If you encounter any problems, please [file an issue] along with a detailed description.

## Acknowledgements

I used [cookiecutter] along with [@hackebrot]'s [cookiecutter-pytest-plugin] template for the boilerplate code of this package. Thanks!

[cookiecutter]: https://github.com/audreyr/cookiecutter
[@hackebrot]: https://github.com/hackebrot
[MIT]: http://opensource.org/licenses/MIT
[BSD-3]: http://opensource.org/licenses/BSD-3-Clause
[GNU GPL v3.0]: http://www.gnu.org/licenses/gpl-3.0.txt
[Apache Software License 2.0]: http://www.apache.org/licenses/LICENSE-2.0
[cookiecutter-pytest-plugin]: https://github.com/pytest-dev/cookiecutter-pytest-plugin
[file an issue]: https://github.com/mgaitan/pytest-portion/issues
[pytest]: https://github.com/pytest-dev/pytest
[pip]: https://pypi.org/project/pip/
[PyPI]: https://pypi.org/project
