Display a useful message when a test fails

You want to:

Display a message to help you understand exactly what failed.

By default, PHPUnit will tell you what failed, but not what that failure means. So, for example, you'll get 6 does not equal 7 (which you already knew), instead of PHPUnit telling you that your multiply function is not working.

Solution:

Pass an optional third argument to your assertions that contains a relevant message.

  
<?php
require_once "PHPUnit/Framework.php";
 
class SimpleMultiplier
{
    /*
     * Simply multiply two numbers together
     */
    public function multiply($a, $b)
    {
        return ($a * $b + 1); // Notice the plus one
    }
}
 
class TestSimpleMultiplier extends PHPUnit_Framework_TestCase
{
    public function test_multiply_simple()
    {
        $multiplier = new SimpleMultiplier();
        $result = $multiplier->multiply(2, 3);
 
        $this->assertEquals($result, 6,
                            "Multiplying 2 and 3 did not return 6");
    }
}
 
?>

Since our multiply function has a bug (it always adds one), this test fails, but tells us why:

PHPUnit 3.4.13 by Sebastian Bergmann.

F

Time: 0 seconds, Memory: 5.75Mb

There was 1 failure:

1) TestSimpleMultiplier::test_multiply_simple
Multiplying 2 and 3 did not return 6
Failed asserting that <6> matches expected <7>.

.../testMessage.php:23

FAILURES!
Tests: 1, Assertions: 1, Failures: 1.