Pest

TestingPHP

What it is

Pest is a testing framework built on PHPUnit with a concise closure-based syntax, expectations API and built-in parallel execution.

Tests are closures passed to test() or it(). The expect() API chains readable assertions, and datasets replace data providers.

Getting started

The smallest useful thing you can do with it, and what each part means.

Tests without classes

php

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it('slugifies a title', function () {
    expect(slugify('Hello World'))->toBe('hello-world');
});

it('rejects an empty title', function () {
    expect(fn () => new Book(''))
        ->toThrow(InvalidArgumentException::class, 'title required');
});

// Datasets replace data providers.
it('slugifies correctly', function (string $input, string $expected) {
    expect(slugify($input))->toBe($expected);
})->with([
    ['Hello World', 'hello-world'],
    ['C++ & Go!', 'c-go'],
]);

// Chained expectations
expect($books)
    ->toHaveCount(3)
    ->each->toBeInstanceOf(Book::class)
    ->and($books[0]->year)->toBeGreaterThan(1900);

`each` applies the following expectation to every element, which replaces a foreach loop of assertions and reports which element failed.

Advanced usage

Where the library earns its place over a simpler alternative.

Hooks, architecture tests and coverage

php

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beforeEach(function () {
    $this->repository = new InMemoryBookRepository();
});

// Architecture tests — enforce structure, not behaviour.
arch('controllers are final')
    ->expect('App\Http\Controllers')
    ->toBeFinal()
    ->toExtend('App\Http\Controllers\Controller');

arch('domain does not depend on the framework')
    ->expect('App\Domain')
    ->not->toUse(['Illuminate', 'Symfony']);

arch('no debug statements')
    ->expect(['dd', 'dump', 'var_dump', 'ray'])
    ->not->toBeUsed();

// vendor/bin/pest --parallel --coverage --min=80

Architecture tests are Pest's distinctive feature: they encode structural rules — layering, finality, forbidden functions — that a linter cannot express and code review otherwise has to enforce by hand.

Errors and fixes

The failures you are most likely to hit, and what actually resolves them.

Call to a member function on null inside a test: $this properties are set in beforeEach. A closure defined outside a test binding will not have them.
Parallel tests interfere: Shared state such as a database or files. Use per-process isolation, or mark those tests to run sequentially.

Best practices

Use arch() tests to enforce layering and catch stray debug calls automatically.
Run with --parallel; test suites of any size benefit substantially.
Adopt incrementally — existing PHPUnit tests keep working alongside Pest ones.
Set --min coverage in CI so coverage cannot silently decline.

Background

Why it exists, and what it was reacting to.

Created by Nuno Maduro, Pest keeps PHPUnit's engine — so every PHPUnit test still works — while replacing the class-per-test-file ceremony with plain functions.

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