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Testing classes for your PHP website with PHPUnit

Archive - Originally posted on "The Horse's Mouth" - 2012-12-20 13:36:47 - Graham Ellis

When you visit a web site and run an application, you want it to just work for you, no matter how complex the stuff in the background might be. If, for example, you want to book a room at Well House Manor then you want a few easy data entries to do everything for you - and you don't really want to be worried or concerned about the background stuff - the way the server creates and uses objects, accesses databases and backroom servers, and ensures that the price is right, the room reserved and not double booked, that confirmation emails have been sent, and that your checkin form will be avaiable at reception.

If you're the developer or maintainer of that web site, however, you want to be able to test and upgrade it in segments. It's not much good if the developer makes a change and finds that the booking system breaks if he's then left struggling through the various elements of code trying to find the cause of the breaks. Much better to break the code into sections and test each section individually.

Test Driven Development (TDD) is a methodology under which you define how your code will work, and how you will test it, from the start. You'll rerun the tests time and time again, and as you write your code you can build up testing each level as you go, and so quickly and efficiently locating any problems.

If you're using PHP, the phpunit package lets you load in an included file (typically containing classes) and then test that code, exercising the methods and objects in the class and asserting the conditions that are expected to exist after each test is run. Within you test class (which extends PHPUnit_Framework_TestCase) you provide a setUp function which prepares each test, and whole series of functions called testXXX where XXX is any name you choose, and you let the PHPUnit program run each of the tests and corralate the results.

Here is a set of test results ... from tests that run correctly:

  [root@pal phpu]# phpunit fivea.php
  PHPUnit 3.5.15 by Sebastian Bergmann.
  
  ...
  
  Time: 0 seconds, Memory: 5.75Mb
  
  OK (3 tests, 4 assertions)
  [root@pal phpu]#

And the same program, run with an introduced error (wanted "Bobby" and got "Bob" from a call to getname) in the second of three tests:

&bsp; [root@pal phpu]# phpunit fivea.php
  PHPUnit 3.5.15 by Sebastian Bergmann.
  
  .F.
  
  Time: 1 second, Memory: 6.00Mb
  
  There was 1 failure:
  
  1) MyTest::testSomething
  Failed asserting that two strings are equal.
  --- Expected
  +++ Actual
  @@ @@
  -Bobby
  +Bob
  
  /root/phpu/fivea.php:55
  
  FAILURES!
  Tests: 3, Assertions: 3, Failures: 1.
  [root@pal phpu]#

To see more - the source of the code we're testing is [here] and the test class is [here]