Using Pest for PHP Tests

Pest provides a concise BDD-style test syntax built on PHPUnit, using test(), it() and expect() for assertions.

What It Does

Pest uses test() and expect() to express behavior. Pest can assert thrown exceptions with closures.

Requirements and Compatibility

Use a supported PHP runtime and install any third-party tool or extension explicitly shown in the examples. Commands should be run from the project root unless stated otherwise.

Syntax, Inputs and Results

The examples separate configuration, the smallest working operation and a realistic follow-up task. Adapt file paths and dependency versions to your own project.

Example 1: Basic Use

Pest uses test() and expect() to express behavior.

<?php
test('discount stays positive', function () {
    $calculate = static fn (int $amount, int $off): int => max(0, $amount - $off);
    expect($calculate(15, 20))->toBe(0);
});

Example 2: Another Case

Pest can assert thrown exceptions with closures.

<?php
it('rejects invalid quantities', function () {
    $validate = static function (int $count): void {
        if ($count < 0) throw new InvalidArgumentException('Bad count');
    };
    expect(fn () => $validate(-1))->toThrow(InvalidArgumentException::class);
});

Practical Example

Run Pest through the project vendor directory.

composer require --dev pestphp/pest
vendor/bin/pest --filter=discount

For production, apply the compatibility and edge-case limits described below.

Important Behavior and Edge Cases

Do not treat Pest syntax as a built-in PHP language feature.

Comparison with Related Functions and Tools

Subject	Key difference
Unit tests vs integration tests	Unit tests isolate one behavior; integration tests use actual interfaces, databases or framework components.

Common Beginner Mistakes

Mistake	Correct approach
Writing tests without meaningful assertions	Assert an exact result or expected exception, including at least one boundary case.
Skipping the prerequisite of this specific workflow	Install or configure the named tool and confirm the example can actually run.
Ignoring edge conditions	Do not treat Pest syntax as a built-in PHP language feature.

Key Takeaways

Pest provides a concise BDD-style test syntax built on PHPUnit, using test(), it() and expect() for assertions.
Do not treat Pest syntax as a built-in PHP language feature.
Keep application configuration, source code and validation tests under version control.

Use these examples as a starting point, then validate the result with the actual PHP build, dependencies and inputs used by your application.