Template method invocation order in python

Question

What would be the simplest way to unit-test run function? Here I'm not interested in what fun* functions do, but only if the order of their invocation is correct.

from mock import Mock

(many, arguments, four, fun) = ('many', 'arguments', 'four', 'fun') 

class TemplateMethod(object):

    def fun1(self, many, parameters, go, here):
        raise NotImplementedError()

    @classmethod
    def fun2(cls, many, parameters, go, here):
        pass

    @staticmethod
    def fun3(many, parameters, go, here):
        pass

    def run(self):
        result1 = self.fun1(many, arguments, four, fun)
        result1.do_something()

        self.fun2(many, arguments, four, fun)
        self.fun3(many, arguments, four, fun)

The only requirement for the solution is non-intrusiveness towards the class under test.

SOLUTION:

This is somewhat of a draft, actually, and this simple class could be fixed and extended in so many ways that I don't care even to think about it. The point is that you can now simply record all the invocations of all the methods in a template method. You can also specify a list of object that shouldn't be mocked by the class (i.e. the function you are recording invocations for).

Special thanks go to @Damian Schenkelman, who gave me some important pointers.

class MockingInvocationRecorder(object):

    FUNCTION_TYPES = ('function', 'classmethod', 'staticmethod')

    def __init__(self, obj, dont_mock_list):
        self._invocation_list = []

        name_list = [exc.__name__ for exc in dont_mock_list]
        self._wrap_memfuns(obj, name_list)

    @property
    def invocations(self):
        return tuple(self._invocation_list)

    def _wrap_single(self, memfun, exclude_list):
        def wrapper(*args, **kwargs):
            self._invocation_list.append(memfun.__name__)

            if memfun.__name__ in exclude_list:
                return memfun(*args, **kwargs)
            else:
                return Mock()

        return wrapper

    def _wrap_memfuns(self, obj, exclude_list):
        for (mem_name, mem) in type(obj).__dict__.iteritems():
            if type(mem).__name__ in self.FUNCTION_TYPES:
                wrapper = self._wrap_single(getattr(obj, mem_name), exclude_list)
                setattr(obj, mem_name, wrapper)

You can now test invocation order by something like this:

tm = TemplateMethod()
ir = MockingInvocationRecorder(tm, [tm.run])

tm.run()

print ir.invocations => ('run', 'fun1', 'fun2', 'fun3')

You can reference a member by class name:

ir = MockingInvocationRecorder(tm, [TemplateMethod.run])

Just be careful that you enlist all the methods that shouldn't be mocked away.

Answer 1

Monkeypatch fun1, fun2, fun3 functions and use a list to keep track of the call order. After that, assert on the list.

Answer 2

Making use of __call__ could be helpful here.

class Function1(object):
    def __call__(self, params, logger=None):
        if logger is not None:
            logger.append(self.__repr__())
        return self.function1(params) 
        # Or no return if only side effects are needed

    def __init__(self, ...):
        #...

    def __repr__(self):
        # Some string representation of your function.

    def function1(params):
        print "Function 1 stuff here..."

Then do something like

class TemplateMethod(object):
    def __init__(self, params):
        self.logger = []
        self.fun1 = Function1(...)
        self.fun1(params, self.logger)

This is pretty hacky; there's probably some ways to clean up what I'm getting at, but encapsulating the functions in classes and then using __call__ is a good way to go.