# Python Pytest Module

`pytest` is a framework that makes building simple and scalable tests easy. Tests are expressive and readable—no boilerplate code required. It is often preferred over the standard `unittest` module for its simpler syntax and powerful features.

## Installation

```bash
pip install pytest
```

## Basic Usage

Create a file named `test_sample.py`. Pytest identifies files starting with `test_` or ending with `_test.py` as test files. Unlike `unittest`, you do not need to create a class.

```python
def func(x):
    return x + 1

def test_answer():
    assert func(3) == 5
```

## Running Tests

Run the tests from the command line:

```bash
pytest
```

## Fixtures

Fixtures provide a fixed baseline upon which tests can reliably and repeatedly execute. They are defined using the `@pytest.fixture` decorator.

```python
import pytest

@pytest.fixture
def input_value():
    return 39

def test_divisible_by_3(input_value):
    assert input_value % 3 == 0

def test_divisible_by_6(input_value):
    assert input_value % 6 == 0
```

## Parametrization

Parametrization allows you to run a test function multiple times with different arguments.

```python
import pytest

@pytest.mark.parametrize("num, output", [(1, 11), (2, 22), (3, 33)])
def test_multiplication_11(num, output):
    assert 11 * num == output
```

## Markers

Markers allow you to categorize tests (e.g., slow, smoke).

```python
import pytest

@pytest.mark.slow
def test_slow_function():
    import time
    time.sleep(1)
    assert True
```

Run with `pytest -m slow`.

## Testing Exceptions

Use `pytest.raises()` to assert that a block of code raises a specific exception.

```python
import pytest

def test_zero_division():
    with pytest.raises(ZeroDivisionError):
        1 / 0
```

[[programming/python/python]]