phpunit/phpunit

Example Code

// --- 1. Create composer.json in your project root ---
// This file defines your project's dependencies and how to autoload classes.
// Run 'composer install' after creating this file to install PHPUnit.
// composer.json content:
{
    "name": "my-project/app",
    "description": "A simple project demonstrating PHPUnit",
    "type": "project",
    "autoload": {
        "psr-4": {
            "App\\": "src/"
        }
    },
    "autoload-dev": {
        "psr-4": {
            "App\\Tests\\": "tests/"
        }
    },
    "require-dev": {
        "phpunit/phpunit": "^9.5"
    },
    "config": {
        "allow-plugins": {
            "php-http/discovery": true
        }
    }
}

// --- 2. Create phpunit.xml in your project root ---
// This file tells PHPUnit where to find your tests and provides other configurations.
// phpunit.xml content:
// <?xml version=\"1.0\" encoding=\"UTF-8\"?>
// <phpunit xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\"
//          xsi:noNamespaceSchemaLocation=\"https://schema.phpunit.de/9.5/phpunit.xsd\"
//          bootstrap=\"vendor/autoload.php\"
//          colors=\"true\"
//          cacheResult=\"false\"
//          failOnRisky=\"true\"
//          failOnWarning=\"true\">
//     <testsuites>
//         <testsuite name=\"Application Test Suite\">
//             <directory>./tests</directory>
//         </testsuite>
//     </testsuites>
//
//     <php>
//         <ini name=\"display_errors\" value=\"On\" />
//         <ini name=\"display_startup_errors\" value=\"On\" />
//     </php>
// </phpunit>

// --- 3. Create src/Calculator.php ---
// This is the class we want to test.
<?php

namespace App;

class Calculator
{
    public function add(int $a, int $b): int
    {
        return $a + $b;
    }

    public function subtract(int $a, int $b): int
    {
        return $a - $b;
    }

    public function multiply(int $a, int $b): int
    {
        return $a * $b;
    }

    public function divide(int $a, int $b): float
    {
        if ($b === 0) {
            throw new \InvalidArgumentException('Cannot divide by zero.');
        }
        return $a / $b;
    }
}

// --- 4. Create tests/CalculatorTest.php ---
// This is the PHPUnit test class for the Calculator.
<?php

namespace App\Tests;

use App\Calculator;
use PHPUnit\Framework\TestCase; // Import PHPUnit's TestCase

class CalculatorTest extends TestCase // Extend PHPUnit\Framework\TestCase
{
    // Test the add method with specific values
    public function testAddNumbers(): void
    {
        $calculator = new Calculator();
        $result = $calculator->add(5, 3);
        $this->assertEquals(8, $result); // Assert that 5 + 3 equals 8
        $this->assertIsInt($result);   // Assert that the result is an integer
    }

    // Test the subtract method
    public function testSubtractNumbers(): void
    {
        $calculator = new Calculator();
        $result = $calculator->subtract(10, 4);
        $this->assertEquals(6, $result);
    }

    // Test the multiply method
    public function testMultiplyNumbers(): void
    {
        $calculator = new Calculator();
        $result = $calculator->multiply(7, 2);
        $this->assertEquals(14, $result);
    }

    // Test the divide method with a valid division
    public function testDivideNumbers(): void
    {
        $calculator = new Calculator();
        $result = $calculator->divide(10, 2);
        $this->assertEquals(5.0, $result); // Use float for comparison
        $this->assertIsFloat($result);
    }

    // Test that dividing by zero throws an expected exception
    public function testDivideByZeroThrowsException(): void
    {
        $calculator = new Calculator();
        // Expect an InvalidArgumentException to be thrown
        $this->expectException(\InvalidArgumentException::class);
        $this->expectExceptionMessage('Cannot divide by zero.');
        $calculator->divide(10, 0); // This call should trigger the exception
    }

    // Example of a data provider for multiple test cases for add method
    /
     * @dataProvider addDataProvider
     */
    public function testAddWithDataProvider(int $a, int $b, int $expected): void
    {
        $calculator = new Calculator();
        $this->assertEquals($expected, $calculator->add($a, $b));
    }

    public function addDataProvider(): array
    {
        return [
            'positive numbers'      => [2, 3, 5],
            'negative numbers'      => [-2, -3, -5],
            'positive and negative' => [5, -3, 2],
            'zero with positive'    => [0, 7, 7],
            'zero with zero'        => [0, 0, 0],
        ];
    }
}

// --- How to run the tests ---
// 1. Create a project directory (e.g., 'my-app').
// 2. Inside 'my-app', create the 'composer.json' and 'phpunit.xml' files as shown above.
// 3. Create 'src/' and 'tests/' directories.
// 4. Place 'Calculator.php' inside 'src/' and 'CalculatorTest.php' inside 'tests/'.
// 5. Open your terminal in the 'my-app' directory.
// 6. Install PHPUnit and other dependencies via Composer:
//    composer install
// 7. Run the tests:
//    ./vendor/bin/phpunit
//
// Expected Output (similar to):
// PHPUnit 9.5.28 by Sebastian Bergmann and contributors.
//
// ...........                                                     11 / 11 (100%)
//
// Time: 00:00.000, Memory: 8.00 MB
//
// OK (11 tests, 11 assertions)