Measuring Test Coverage in PHP

Code coverage reports identify which statements and branches a PHP test suite executes; they do not measure assertion quality.

What It Does

Generate a terminal coverage overview. Generate an XML report for CI.

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

Generate a terminal coverage overview.

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

Example 2: Another Case

Generate an XML report for CI.

XDEBUG_MODE=coverage vendor/bin/phpunit --coverage-clover build/coverage.xml

Practical Example

Exercise the independent branches with three inputs.

<?php
function shippingFee(int $amount): int {
    if ($amount <= 0) return 0;
    return $amount < 100 ? 5 : 0;
}
var_dump(shippingFee(0), shippingFee(50), shippingFee(120));

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

Important Behavior and Edge Cases

A high percentage still permits wrong logic, missed boundary cases and false-positive assertions.

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	A high percentage still permits wrong logic, missed boundary cases and false-positive assertions.

Key Takeaways

Code coverage reports identify which statements and branches a PHP test suite executes; they do not measure assertion quality.
A high percentage still permits wrong logic, missed boundary cases and false-positive assertions.
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.