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Tutorial --  A short introduction to the test framework

Why using the test framework?

PHPUnit gives you a simple framework for creating a test application to automate testing of functions and classes. PHPUnit is inspired by JUnit. Kent Beck and Erich Gamma created JUnit as a tool for eXtreme Programming. One of the parts of XP is to test small software components as often and early as possible and not to fix bugs and errors in the API while setting up and testing the whole application. You have not to switch to XP to benefit from PHPUnit. It is a good tool for testing classes or a set of functions and helps you to avoid endless debug sessions.

Work routine

Normal, 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:

This seems to 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.

Design a class

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) {        
    }    
}    
?>

Creating test suite

Now we can create a test suite, which checks every function of your string class. A test suite is 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 compare must delegate to a function of the assert*()-family, which decides if a function pass or fail the test. 
---- testcase.php ----

<?php

require_once 'string.php';
require_once 'PHPUnit/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); 
    }        
  }
?>

The first test run

Now, we can run a first test. Execute this PHP program. Make sure that the paths are correct. 
---- stringtest.php ----    
    
<?php

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

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

echo $result -> toString();
?>

If you call this script through commandline, you will get this 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 in a correct html page and call $result->toHTML () instead of $result->toString().

Implementation

Ok, let's start with implementation of the 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;      
    }    
}    
?>

Implementing is done and run the test again: 
~> 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 did a typing mistake. Change line 16 in string.php to 
$this->data = $this->data.$string->toString("%s");
and run the test again: 
~> php -f stringtest.php
TestCase stringtest->testtostring() passed
TestCase stringtest->testcopy() passed
TestCase stringtest->testadd() passed
Everything is ok now!

Conclusion

Hm, such a big expenditure for testing three simple functions? Don't forget, this is a small example. Thing about bigger, complexer API's like database abstraction or basket classes in a shop application. PHPUnit is an excellent tool to detect errors in the implementation. Maybe you have a big class used in a few applications and you want to reimplement the class. With a test suite, you can easily check and fix the new implementation in a short session.

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