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Accumulo, mail # dev - Mocking framework


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Re: Mocking framework
Drew Farris 2011-10-27, 17:55
I agree in principle without having reviewed the tests accompanying ACCUMULO-53.

I've used EasyMock in the past and have been very happy with the
ability to programatically mock implementations of interfaces, define
test input and assert a proper sequence of calls, and output. In
general I think mock object testing is a useful tool, especially in
cases where the existing interface implementations have heavyweight
external dependencies, such as for mocking JDBC result sets or
portions of the Hadoop framework. I've used mock objects to write unit
tests for mappers and reducers by mocking out the hadoop context,
counters, etc. Arguably this would be have been better achieved with
MRUnit, which wasn't on my radar at the time.

I found that I didn't have to jump through hoops to make code
testable. Private methods could really be private instead of protected
or public in order to facilitate testing. I also appreciate the
ability to not only assert return values, but assert a series of
method calls and side effects.

The danger with this is only testing in isolation using mocks -- If
the mocks don't follow the contract or conventions the implementations
the tests are useless or deceptive. Implementation class behavior can
change in ways that are invisible from an api perspective, so it's
important that these sorts of changes be reflected adequately by the
mocks themselves. Coupled with adequate integration tests this danger
is minimized. Generally I think the tradeoff in increased testability
makes up for these drawbacks.

Drew

On Thu, Oct 27, 2011 at 12:49 PM, Jesse Yates <[EMAIL PROTECTED]> wrote:
> Hi all,
>
> Currently Accumulo doesn't have any mocking framework. However, in some
> recent work (ACCUMULO-53) doing good testing was greatly facilitated by
> adding in a mocking framework. They make it easy to only test the piece of
> the architecture that we are interested in testing, helping to isolate and
> ensure that we are really fixing problems in the code.
>
> So, I would like to propose adding the following test-time dependencies for
> testing:
>
> EasyMock (http://easymock.org/)
> This is a really popular mocking framework for java and is really easy to
> use. I've rarely run into a situation that wasn't covered with what EasyMock
> does.
>
> PowerMock (http://code.google.com/p/powermock/)
> This is the utility to cover what other mocking frameworks (including
> Mockito) can't do - capturing creation of objects (new Whatever(...)) and
> returning mocks instead, mocking static calls, mocking standard java lib
> calls, and accessing private methods/fields.
>
> This combination has proven to be incredibly effective and easy to use in
> the past, allowing for a really comprehensive testing suite.
>
>  If you want to see an example of this stuff in action, check out the patch
> 'java_ACCUMULO-53_v2.patch' on ACCUMULO-53.
>
> What does everyone think?
>
> Thanks!
> --Jesse
>
> -------------------
> Jesse Yates
> 240-888-2200
> @jesse_yates
>