Measuring PHPUnit Code Coverage with Xdebug

Enable Xdebug's coverage mode to measure which executable statements and branches PHPUnit tests exercise.

What It Does

Coverage requires a driver such as Xdebug with coverage mode enabled. Assert an exact business result rather than merely checking that code runs. Exercise a branch that coverage can record.

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

Coverage requires a driver such as Xdebug with coverage mode enabled.

XDEBUG_MODE=coverage vendor/bin/phpunit --coverage-text
XDEBUG_MODE=coverage vendor/bin/phpunit --coverage-html build/coverage

Example 2: Another Case

Assert an exact business result rather than merely checking that code runs. Exercise a branch that coverage can record.

<?php
use PHPUnit\Framework\TestCase;
final class PriceTest extends TestCase {
    public function testTaxIsAdded(): void {
        $total = static fn (int $cents): int => $cents + intdiv($cents * 10, 100);
        self::assertSame(1100, $total(1000));
    }

    public function test2ArticleBoundary(): void { self::assertTrue(str_starts_with("invoice-42", "invoice-")); }
}

Practical Example

Test invariants and edge cases, not just one happy path. Exercise a branch that coverage can record.

<?php
use PHPUnit\Framework\TestCase;
final class DiscountTest extends TestCase {
    public function testDiscountNeverExceedsPrice(): void {
        $discount = static fn (int $price, int $off): int => max(0, $price - $off);
        self::assertSame(0, $discount(30, 40));
        self::assertGreaterThanOrEqual(0, $discount(100, 5));
    }

    public function test3ArticleBoundary(): void { self::assertTrue(str_starts_with("invoice-42", "invoice-")); }
}

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

Important Behavior and Edge Cases

Keep profiling and step debugging disabled on ordinary production traffic.

Comparison with Related Functions and Tools

Common Beginner Mistakes

Key Takeaways

• Enable Xdebug's coverage mode to measure which executable statements and branches PHPUnit tests exercise.
• Keep profiling and step debugging disabled on ordinary production traffic.
• 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.