Re: [Mockobjects-java-users] EasyMock vs. MockObjects

[Vincent M. <vm...@oc...>]

----- Original Message -----
From: "Lucas Filz" <lu...@ha...>
To: <moc...@li...>
Sent: Friday, September 14, 2001 7:31 PM
Subject: [Mockobjects-java-users] EasyMock vs. MockObjects


> Up to now I'm just reading about all that, and maybe I have missed
something,
> but:
>
> Why creating, handling, refactoring all those MockObjects when there is
such a
> thing as EasyMock? (Writing an interface if there is none is not the point
I
> guess.)
>
> What are the disadvantages in using EasyMock?
>
> Or, what are the advantages in having the "real mock object" at hand?
>

The short answer is : the two methods (dynamic and static) are
complementary. Why ? Because it is not always possible to generate good mock
implementations. I'll give a simple example. Lets imagine you want to use a
mock implementation of ServletOutputStream because you'd like to assert the
result from an HTTP response. This class only has print() methods but no
getter to access the content. Also what you'd like to do is to assert the
full string that has been written to the stream and not byte by byte. This
requires some intelligence that cannot be implemented automatically by
EasyMock or a static generation (MockMaker). You'll also find that you'll
discover patterns in your test case and you'll want to factorise these
patterns in the mock objects to provide consistency of checks and easier
writing of tests.

Now, it probably depends on the kind of API you are mocking and some will be
easily mocked with EasyMock. Others won't. I guess that a practice would be
to use automatic generation (be it dynamic or static) and then manually
write or modify the mocks (for those statically generated). Thus, the
problem is that EasyMock or MockMaker won't provide in-the-box and ready to
use mock objects (some will need to be written by hand or modified).

The idea of the Mock Objects project is twofold : provide a core framework
of expectations and useful classes for writing mock implementations (This
framework is actually used by MockMaker to generate mock objects and it
could be used by EasyMock too) and some prepackaged and already written mock
implementations for some standard APIs. The idea is that these API will be
feature complete (ok, I agree, there is still some work to be done ... :) )
and will have been fine tuned to already provide the patterns I mentionned
above (i.e. shortcuts for easy testing).

Tell me what you think. I'd like to hear from others too.

Thanks
-Vincent Massol