Add some automatic tests to the module

I think the best approach for testing smiley text filter (function smiley_filter_process) is the Unit testing (DrupalUnitTestCase), not Functional testing (DrupalWebTestCase), because in fact it is a unit - we should give it an input (text with smileys codes) and get an output (text with smiles converted into images). But we have a problem -
current version of this function requires a database to fetch an array of smileys objects (function smiley_get_all()). So we need to slightly refactor this function like this:

function smiley_filter_process($text, $filter, $format) {
  $smileys = smiley_get_all();
  return smiley_process_text($text, $smileys);
}

function smiley_process_text($text, $smileys) {
... rest of the code 
}

After thaе we should define an array with objects of smiles in our test cases manually, like this:

    $smileys = array (
      (object) array (
        'sid' => '45',
        'uri' => 'kolobok/smile.gif',
        'status' => '1',
        'acronyms' => '*smile* :-) :) +) =) :smile:',
        'description' => 'Smile',
      ),    
    );

and then we could run tests:

$original_text = 'simple text with :) in it';
$expected_text = 'simple text with <img[^>]*> in it';
$new_text = smiley_process_text($original_text, $smileys);
$this->assertTrue(preg_match($expected_text, $new_text), t('All smileys were replaced correctly.'));

How do you think, is my approach ok? Should i further work in that direction?
I attached my current working code for you for better understanding what i mean.