# PHPUnit — The Standard Testing Framework for PHP

> PHPUnit is the de facto unit testing framework for PHP, providing assertions, mocks, and code coverage analysis.

## Install

Save as a script file and run:

# PHPUnit — The Standard Testing Framework for PHP

## Quick Use
```bash
# Install via Composer
composer require --dev phpunit/phpunit

# Write a test in tests/ExampleTest.php
# Run it
./vendor/bin/phpunit tests/
```

## Introduction
PHPUnit is the most widely adopted testing framework in the PHP ecosystem. Created by Sebastian Bergmann, it brings xUnit-style testing to PHP with a comprehensive assertion library, built-in mocking, and code coverage reporting. Almost every major PHP framework and CMS integrates with PHPUnit out of the box.

## What PHPUnit Does
- Provides over 60 assertion methods for values, arrays, strings, exceptions, and output
- Includes a built-in mock object framework for stubs, spies, and expectations
- Generates code coverage reports in HTML, Clover XML, and Cobertura formats
- Supports data providers for parameterized test methods
- Integrates with CI pipelines via JUnit XML output

## Architecture Overview
PHPUnit runs as a CLI tool that discovers test classes extending `TestCase`. The runner reflects on each class to find methods prefixed with `test` or annotated with `#[Test]`. Each test method executes in an isolated instance so that object state does not persist between tests. Coverage collection uses either Xdebug, PCOV, or php-code-coverage as the driver, instrumenting source files to track executed lines and branches.

## Self-Hosting & Configuration
- Install globally via Composer or as a project-level dev dependency
- Configure with `phpunit.xml` for test suites, bootstrap files, and coverage filters
- Use `--filter` to run specific test methods or classes by name pattern
- Enable `--testdox` for human-readable output that documents behavior
- Set `XDEBUG_MODE=coverage` when collecting coverage with Xdebug 3+

## Key Features
- Rich assertion API covers types, arrays, JSON, XML, files, and regular expressions
- Data providers generate multiple test runs from arrays or generators
- Mock builder supports interface mocking, method stubbing, and invocation counting
- Code coverage with line, branch, and path-level granularity
- Attributes (PHP 8.1+) replace docblock annotations for cleaner metadata

## Comparison with Similar Tools
- **Pest** — a wrapper around PHPUnit with a more concise syntax; PHPUnit offers the underlying engine and full API
- **Codeception** — higher-level acceptance and functional testing; PHPUnit focuses on unit and integration tests
- **PHPSpec** — spec-driven development approach; PHPUnit follows the classic xUnit pattern
- **Behat** — BDD with Gherkin syntax; PHPUnit provides assertion-based tests without a domain language layer
- **SimpleTest** — an older PHP testing library now largely superseded by PHPUnit

## FAQ
**Q: Which PHP versions does PHPUnit support?**
A: PHPUnit 11 requires PHP 8.2+. Older PHPUnit branches support earlier PHP versions.

**Q: How do I run PHPUnit tests in parallel?**
A: Use the `paratest` package, which wraps PHPUnit and distributes tests across multiple processes.

**Q: Can PHPUnit test Laravel applications?**
A: Yes. Laravel ships with PHPUnit pre-configured and provides helper traits for HTTP, database, and queue testing.

**Q: Does PHPUnit support snapshot testing?**
A: Not natively. Use the `spatie/phpunit-snapshot-assertions` package for snapshot comparisons.

## Sources
- https://github.com/sebastianbergmann/phpunit
- https://docs.phpunit.de/

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