SimpleTest Tutorial (Drupal 7)

Note: The code for this tutorial is maintained in the Examples for Developers module. This means:

• You can grab a copy there and fiddle with it, change it, experiment with it.
• If you find problems, file an issue there and get it fixed. Patches and improvements are welcome.

This tutorial will take you through the basics of testing in Drupal. By the end you should be able to write your first test! For this example we will create a dummy module called "simpletest_example", which provides a content type called "simpletest_example". This content type is exactly the same as any basic Drupal node type (e.g., 'page'). The tutorial will then explain how to test this simpletest_example content type to ensure it functions properly.

Setup for the tutorial

First, we will need to make sure that the Simpletest module is installed.
In Drupal 7, Simpletest is part of the core and is called Testing.
If you have not done so already, you will need to make sure the Simpletest module is enabled.
Simpletest verbose testing information is on by default in Drupal 7, but you need it and may want to check to make sure it's turned on. It gives you a screenshot of what the Drupal page looks like at every point in the test. Check it at admin/config/development/testing/settings.
This tutorial makes use of the Simpletest Example module from http://drupal.org/project/examples.

How Drupal's Simpletest works

Most of Drupal is web-oriented functionality, so it's important to have a way to exercise these functions. Simpletest creates a complete Drupal installation and a virtual web browser and then uses the virtual web browser to walk the Drupal install through a series of tests, just like you would do if you were doing it by hand. It's terribly important to realize that each test runs in a completely new Drupal instance, which is created from scratch for the test. In other words, none of your configuration and none of your users exists! None of your modules are enabled beyond the default Drupal core modules. If your test sequence requires a privileged user, you'll have to create one (just as you would if you were setting up a manual testing environment from scratch). If modules have to be enabled, you have to enable them. If something has to be configured, you'll have to use Simpletest to do it, because none of the configuration on your current site is in the magically created Drupal instance that we're testing. None of the files in your files directory are there, none of the optional modules are installed, none of the users are created. We have magic commands to do all this within the Simpletest world, and we'll get to that in a little bit.

About the Simpletest Example module

The Simpletest Example module provides a custom node type (like 'page' or 'story'). It has a title and a body. That's it. It gives us a chance to demonstrate testing of content creation. To implement the node, we have to provide the node type to Drupal with hook_node_info() and provide a form for the node type with hook_form(). We implement permissions for the module (so that you need "create simpletest_example content" permissions to create one, or "edit own simpletest_example content" permissions to edit one.) And of course we need a simpletest_example.info.
Note that our module has a bug in it: The permissions handling is not done correctly. So even though there's a permission string for 'edit own simpletest_example', it's not handled correctly by simpletest_example_access(), so when our properly privileged user tries to edit a node, it can't. Of course, the manual user tester was probably testing with user 1, so never saw this failure case. We'll get to this later.

This code is maintained in the Examples for Developers module. It really helps to try out the code, change it a bit, experiment with dummy code like this before trying to do something serious.
You're encouraged to grab it, enable the module, and work with the code.

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Source: http://drupal.org/simpletest-tutorial-drupal7