Mocking Functions in Simple Test

When dealing with external projects that you either want to re-use parts of or refactor, being able to write unit tests is often a big problem, especially if it’s written in procedural code like;

function aFunctionIWantToTest($foo) {
    $foo = aFunctionIDontWantToTest($foo);
}
 
function aFunctionIDontWantToTest($foo) {
    global $conf; // aaargh!
 
    if ( $conf['reevaluateMeEveryTime'] ) {
        doSomethingPainful($foo);
    } else {
        ohGodAndAnotherFunction($foo);
    }
}

Being able to “mock” aFunctionIDontWantToTest in a similar manner to Mock Objects would be a big help.

Brought this up a while back here on the SimpleTest feature tracker and sent a mail today to the SimpleTest list with an initial implementation.1).

After discovering APD's (at least in the old 0.4 version I was using) rename_function does very wierd things settled on runkit as the tool to help “mock” a function, which so far seems to work fine. Be warned you can rename anything including pre-defined PHP functions - lots to room to shoot yourself in the foot.

Example use (testing this);

class html_hilight_test extends UnitTestCase {
  
  function testHighlightTwoWords() {
 
    MockFunction::generate('unslash');
 
    $html = 'Foo bar Foo php Foo';
 
    MockFunction::setReturnValueAt(0,'unslash','bar');
    MockFunction::setReturnValueAt(1,'unslash','php');
    MockFunction::expectCallCount('unslash',4);
 
    $this->assertPattern(
      '/Foo <span.*>bar<\/span> Foo <span.*>php<\/span> Foo/',
      html_hilight($html,'bar php')
      );
 
    MockFunction::restore('unslash');
  }
}

Basically the methods are all the same as normal SimpleTest mock objects but are called statically via the the MockFunction class.

Note: you must call MockFunction::restore() yourself when you’re finished, otherwise you’ll have mock functions “lying around”, which may lead to very hard to debug problems when running other tests

Source code available here: mockfunctions.tar.gz