Based on the python-ideas thread about closures, I realised there are two features the inspect module could offer to greatly simplify some aspects of testing closure and generator behaviour:

  inspect.getclosure(func)
    Returns a dictionary mapping closure references from the supplied function to their current values.

  inspect.getgeneratorlocals(generator)
    Returns the same result as would be reported by calling locals() in the generator's frame of execution

The former would just involve syncing up the names on the code object with the cell references on the function object, while the latter would be equivalent to doing generator.gi_frame.f_locals with some nice error checking for when the generator's frame is already gone (or the supplied object isn't a generator iterator).