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.
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
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 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.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 a first test. Execute this PHP program. Make sure that the paths are correct.
---- 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 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 |
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().
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 |
$this->data = $this->data.$string->toString("%s"); |
~> php -f stringtest.php TestCase stringtest->testtostring() passed TestCase stringtest->testcopy() passed TestCase stringtest->testadd() passed |
Hm, such a big expenditure for testing three simple functions? Don't forget, this is a small example. Think 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.