`pytest` is an essential Python library for developers focused on testing their code. It provides a powerful yet simple framework for writing and running tests, supporting unit tests, functional tests, and more complex test scenarios. `pytest` stands out for its ease of use, detailed assertions, fixtures for setup and teardown, and support for parameterized testing, among other features. Here's a concise reference guide for common use cases with `pytest`:


# `pytest` Reference Guide

## Installation
```
pip install pytest
```

## Basic Usage

### Writing Your First Test
Tests are Python functions that start with `test_`. Place your test functions in files named `test_*.py` or `*_test.py`.

```python
# content of test_sample.py
def func(x):
    return x + 1

def test_answer():
    assert func(3) == 4
```

### Running Tests
Navigate to the directory containing your test file and run:
```
pytest
```
`pytest` will discover and run all tests following its naming conventions.

## Assertions
`pytest` uses standard Python `assert` for verifying expectations and values in tests, providing detailed output on assertion failures.

```python
def test_check_equal():
    assert func(4) == 5
```

## Fixtures
Fixtures provide a powerful mechanism for setup and teardown operations, creating test data, and configuring the test environment.

```python
import pytest

@pytest.fixture
def input_value():
    return 38

def test_divisible_by_2(input_value):
    assert input_value % 2 == 0
```

## Parameterized Tests
Parameterize tests to run the same test function with different inputs.

```python
@pytest.mark.parametrize("test_input,expected", [(1, 2), (2, 3), (3, 4)])
def test_eval(test_input, expected):
    assert func(test_input) == expected
```

## Handling Exceptions
Test that a certain exception is raised using the `pytest.raises` context manager.

```python
def test_exception():
    with pytest.raises(ValueError):
        raise ValueError
```

## Skipping Tests
Skip a test function or expect it to fail.

```python
@pytest.mark.skip(reason="not implemented yet")
def test_to_skip():
    pass

@pytest.mark.xfail
def test_might_fail():
    pass
```

## Using Plugins and Integrations
`pytest` supports numerous plugins for integration with other tools and extending its functionality, such as `pytest-django` for Django projects, `pytest-asyncio` for testing asyncio code, and many more.

## Configuration
Use a `pytest.ini`, `tox.ini`, or `pyproject.toml` file to configure `pytest` behavior, like custom markers, test paths, and plugin configurations.

## Advanced Usage
`pytest` offers a broad spectrum of advanced features, including but not limited to test fixtures scopes, using mocks, and integrating with continuous integration (CI) tools.

## Continuous Integration
`pytest` can easily integrate with CI tools like Jenkins, GitHub Actions, or GitLab CI, running your test suite on every push or pull request automatically.

`pytest` simplifies and accelerates the testing process, encouraging best practices in test writing and execution. Its extensive documentation and active community make it a go-to choice for Python developers looking to ensure their code meets the highest standards of quality.


`pytest` is favored in the Python community for its rich ecosystem, simplicity, and ability to handle not just simple unit tests but also complex functional testing for applications and libraries.