PHP Unit Test Module - - -

PHPUnit provides a simple framework for creating a test suite to automate the testing of functions and classes. PHPUnit is inspired by JUnit which was created by Kent Beck and Erich Gamma as a tool for eXtreme Programming. One of the rules of XP is to test small software components as often and early as possible, this way you will not have to fix bugs and errors in the API while setting up and testing larger applications that depend on the class. While unit testing is one of the fundamental rules in XP, you don’t have to switch to XP to benefit from PHPUnit. PHPUnit stands alone as a good tool for testing classes or a set of functions and will ease your development cycle and help you to avoid endless debug sessions.

Normally, you would write a class, do some unsystematic tests using echo() or var_dump(). After this, you use the class in your application and hope everything is ok. To benefit from PHPUnit you should rethink the flow. The best way is to do this:

1. design your class/API

2. create a test suite

3. implement the class/API

4. run the test suite

5. fix failures or errors and go to #4 again

It may seem that this will require a lot of time, but this impression is wrong. Creating the test suite using PHPUnit needs only a few minutes and running the test suite only seconds.

Let’s start with a small example: a string class. First, we create a bunch of functions declarations to work on a string:

—- string.php —-

<?php
class String
{
 //contains the internal data
 var $data;

 // constructor
 function String($data) {
 $this->data = $data;
 }
 // creates a deep copy of the string object
 function copy() {
  }

  // adds another string object to this class
  function add($string) {
  }

 // returns the formated string
 function toString($format) {
  }
  }
  ?>

Now we can create a test suite, which checks every function of your string class. A test suite is a normal PHP class inherited from PHPUnit_TestCase containing test functions, identified by a leading ‘test’ in the function name. In the test function, an expected value has to be compared with the result of the function to test. The result of this comparison must delegate to a function of the assert*()-family, which decides if a function passes or fails the test.

—- testcase.php —-

<?php

require_once 'string.php';
require_once 'PHPUnit.php';

class StringTest extends PHPUnit_TestCase
{
  // contains the object handle of the string class
  var $abc;

  // constructor of the test suite
  function StringTest($name) {
     $this->PHPUnit_TestCase($name);
  }

  // called before the test functions will be executed
  // this function is defined in PHPUnit_TestCase and overwritten
  // here
  function setUp() {
      // create a new instance of String with the
      // string 'abc'
      $this->abc = new String("abc");
  }

  // called after the test functions are executed
  // this function is defined in PHPUnit_TestCase and overwritten
  // here
  function tearDown() {
      // delete your instance
      unset($this->abc);
  }

  // test the toString function
  function testToString() {
      $result = $this->abc->toString('contains %s');
      $expected = 'contains abc';
      $this->assertTrue($result == $expected);
  }

  // test the copy function
  function testCopy() {
    $abc2 = $this->abc->copy();
    $this->assertEquals($abc2, $this->abc);
  }

  // test the add function
  function testAdd() {
      $abc2 = new String('123');
      $this->abc->add($abc2);
      $result = $this->abc->toString("%s");
      $expected = "abc123";
      $this->assertTrue($result == $expected);
   }
  }
  ?>

Now, we can run the first test. Make sure that all the paths are correct and then execute this PHP program.

—- stringtest.php —-

<?php

require_once 'testcase.php';
require_once 'PHPUnit.php';

$suite  = new PHPUnit_TestSuite("StringTest");
$result = PHPUnit::run($suite);

echo $result -> toString();
?>

If you call this script from the commandline, you will get the following output:

 TestCase stringtest->testtostring() failed: expected true, actual false
 TestCase stringtest->testcopy() failed: expected , actual Object
 TestCase stringtest->testadd() failed: expected true, actual false
Every function fails the test because your string functions didn't returned what we defined as the expected value.

If you want to call the script through your browser, you have to put the script on a correct Html page and call 
 $result->toHTML () 
 instead of $result->toString().

Ok, let’s start with the implementation of our string class.

—- string.php —-

<?php
class String
{
  //contains the internal data
  var $data;

  // constructor
  function String($data) {
      $this->data = $data;
  }

  // creates a deep copy of the string object
  function copy() {
      $ret = new String($this->data);
      return $ret;
  }

  // adds another string object to this class
  function add($string) {
      $this->data = $this->data.$string->toString("%ss");
  }

  // returns the formated string
  function toString($format) {
      $ret = sprintf($format, $this->data);
      return $ret;
  }
 }
 ?>

~>
php -f stringtest.php
TestCase stringtest->testtostring() passed
TestCase stringtest->testcopy() passed
TestCase stringtest->testadd() failed: expected true, actual false
D'oh! the last test failed! We made a typing mistake. Change line 16 in string.php to
<?php
$this->data = $this->data.$string->toString("%s");
?>

~>
php -f stringtest.php
TestCase stringtest->testtostring() passed
TestCase stringtest->testcopy() passed
TestCase stringtest->testadd() passed``

Everything is now OK!