Drupal 7 Module Development

Chapter 2
This function does three things.
First, it runs a function called module_invoke(), storing its results in $info. The
module_invoke() function calls a particular hook for a particular module.
This function is the infrequently used counterpart of
module_invoke_all(), which executes a hook in all
of the modules in which that hook appears.
The module_invoke() method takes two parameters: The name of the module
and the name of the hook to call. The call in this code, module_invoke('first',
'block_info') is semantically equivalent to calling first_block_info(). Our only
advantage gained here is in ensuring that it can be called through the hook system.
Basically, then, we have simulated the circumstances under which our block info
hook would have been executed by Drupal. The next thing to do is ensure that the
information returned by our hook is as expected.
We do this by making a couple of statements—assertions, about what we expect. The
testing framework then validates these exceptions. If the code functions as expected,
the test passes. If not, the test fails.
Here are the two tests:
$this->assertEqual(1, count($info),
t('Module defines a block.'));
$this->assertTrue(isset($info['list_modules']),
t('Module list exists.'));
(Note that each of these two lines were split onto one line for formatting.)
Each assertion is typically of the form $this->assertSOMETHING($conditions,
$message), where SOMETHING is a type of assertion, $conditions are the conditions
that must be satisfied for the test to pass, and $message is a message describing
the test.
In our first test, the test asserts that 1 and count($info) should be equal. (The
message is simply used by the testing interface to show what it was testing.)
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