unittest help

[André Malo]

* "Qiangning Hong" <hongqn at gmail.com> wrote:

> I want to apply TDD (test driven development) on my project.  I am
> working on a class like this (in plan):
> 
> # file: myclass.py
> import _extmod
> 
> class MyClass(object):
>     def __init__(self):
>         self.handle = _extmod.open()
> 
>     def __del__(self):
>         _extmod.close(self.handle)
> 
>     def some_stuff(self):
>         _extmod.foobar(self.handle)
> 
>     ...
> 
> As you see, it is an OO wrapper on _extmod, which is a pyrex extension
> module.  The question is: how to unittest this class?  As the _extmod
> is hardware-dependent, I want to use a mock class to replace it in unit
> test.  But how can I let myclass in unittest to import the mock class?

You need to design for testability, meaning in this case, that your class could
to do something like this:

class MyClass(object):
    def __init__(self):
        self._loadExtmod()
        self.handle = self._extmod.open()

    def __del__(self):
        self._extmod.close(self.handle)

    def _loadExtmod(self):
	import _extmod
        self._extmod = extmod

    def some_stuff(self):
        self._extmod.foobar(self.handle)

Now just overload _loadExtmod and provide the mock class there.

HTH, nd