PHPUnitTest Dependencies

PHPUnit supports the declaration of explicit dependencies between test methods. Such dependencies do not define the order in which the test methods are to be executed but they allow the returning of an instance of the test fixture by a producer and passing it to the dependent consumers.

• A producer is a test method that yields its unit under test as return value.

• A consumer is a test method that depends on one or more producers and their return values.

Using the @depends annotation to express dependencies between test methods.

 

<?php
class StackTest extends PHPUnit_Framework_TestCase
{
    public function testEmpty()
    {
        $stack = array();
        $this->assertEmpty($stack);
 
        return $stack;
    }
 
    /**
     * @depends testEmpty
     */
    public function testPush(array $stack)
    {
        array_push($stack, 'foo');
        $this->assertEquals('foo', $stack[count($stack)-1]);
        $this->assertNotEmpty($stack);
 
        return $stack;
    }
 
    /**
     * @depends testPush
     */
    public function testPop(array $stack)
    {
        $this->assertEquals('foo', array_pop($stack));
        $this->assertEmpty($stack);
    }
}
?>

 

In the example above, the first test, testEmpty(), creates a new array and asserts that it is empty. The test then returns the fixture as its result. The second test, testPush(), depends on testEmpty() and is passed the result of that depended-upon test as its argument. Finally, testPop() depends upon testPush().

To quickly localize defects, we want our attention to be focussed on relevant failing tests. This is why PHPUnit skips the execution of a test when a depended-upon test has failed. This improves defect localization by exploiting the dependencies between tests as shown below

<?php
class DependencyFailureTest extends PHPUnit_Framework_TestCase
{
    public function testOne()
    {
        $this->assertTrue(FALSE);
    }
 
    /**
     * @depends testOne
     */
    public function testTwo()
    {
    }
}
?>

phpunit --verbose DependencyFailureTest
PHPUnit 3.7.0 by Sebastian Bergmann.

FS

Time: 0 seconds, Memory: 5.00Mb

There was 1 failure:

1) DependencyFailureTest::testOne
Failed asserting that false is true.

/home/sb/DependencyFailureTest.php:6

There was 1 skipped test:

1) DependencyFailureTest::testTwo
This test depends on "DependencyFailureTest::testOne" to pass.


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

 A test may have more than one @depends annotation. PHPUnit does not change the order in which tests are executed, you have to ensure that the dependencies of a test can actually be met before the test is run.