Who Practices Test-Driven Development (TDD)?

• Tue, 28 Mar 2006 at 03:18:40 GMT
• 0 Comments
• References

Harry Fuecks maintains a good blog over at Sitepoint and recently wrote a piece on Evaluating PHP Applications.

Noel Darlow, a regular contributor to the Sitepoint forums (and someone whose opinion I respect), comments:

I think testing is a good indicator of the developer's ability. I'll be looking for tests being used to drive the design and not just the odd unit test stuck on after the fact.

I'm a big advocate of testing, and although I won't claim to be an expert on the topic, I have to question whether it's necessary that tests drive the design. It seems plausible that someone could choose to write tests after the implementation, and I don't think ignorance is necessarily the reason.

On the other hand, I find myself taking this approach more and more. For example, when I'm designing a function or class, I start with an example that describes how I want to use it:

<?php 
 
$auth = new myAuth; 
 
$auth->username = 'chris'; 
$auth->password = 'mypass'; 
 
if ($auth->checkLogin()) { 
    /* SUCCESS */ 
} else { 
    /* FAILURE */ 
} 
 
?>

(Sorry if my ad hoc example doesn't live up to your standards.)

I'll usually type this out at least once, so it's not just imagined. In order to implement myAuth, I can choose to keep this example in mind as I write the code, or I can take this simple example and turn it into a real test or two:

<?php 
 
include 'test-more.php'; 
 
plan(2); 
 
$auth = new myAuth; 
 
{ 
    /* Test Valid Credentials */ 
    $auth->username = 'chris'; 
    $auth->password = 'mypass'; 
 
    ok($auth->checkLogin(), 'test valid credentials'); 
} 
 
{ 
    /* Test Invalid Credentials */ 
    $auth->username = 'chris'; 
    $auth->password = 'notmypass'; 
 
    ok(!$auth->checkLogin(), 'test invalid credentials'); 
} 
 
?>

It's so easy to write tests, I might even write some for a blank username, blank password, etc. I can do all this without writing a single line of code, and when I begin writing the code, I already have a simple test suite to run - I don't have to write some quick ad hoc tests just to see whether things are working as planned. When all the tests pass, I know I've accomplished my initial design goals.

How many of you test? How many of you write your tests first?

Note: If you happen to be attending PHP Quebec later this week, I'm giving a talk that will discuss some simple approaches to testing.