[TIP] Testing with Databases

[Mark Roddy]

On Sun, Jul 18, 2010 at 3:08 PM, Alfredo Deza <alfredodeza at gmail.com> wrote:
> Hi,
> I am building test cases for a middleware app that uses a database to store
> some data.
> Although I am using MongoDB, my question should be regardless of the
> database being used.
> What would you guys recommend to correctly test database behavior related to
> my application?
> Should I rely on expecting a working database when the application is
> installed?
> Is it OK to mock MongoDB? (or any other DB being used). I know mocking is OK
> but might get brittle
> tests if it gets overused.
> Maybe even a combination of both: mock some parts but still have certain
> tests that will definitely require
> an instance of the database running which could potentially prevent version
> changes that break the app.
> Any recommendations as to how to deal with database functionality testing
> would be great.
>
> Thanks!
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>

These are my 2 cents as someone whose worked with a lot of db app:

1) Unit test application side behavior independent of the db.  This
will likely require mocking, which is ok.
2) Write integration tests to execute any database side behavior/logic
(don't think this would be something needed with mongodb).
3) Some set of integration tests should also include application and
db side to make sure they play nice together.
3) When executing tests as part of an automated build/Continuous
Integration, 'configure' the database along with any test setup prior
to running about integration tests (such as schema setup and
sample/test data loading), don't run against an instance sitting
around as you don't know what state it will be in.  This leads to a
maintenance headache of having to remember to upgrade the instance and
has the danger of out of date schema/data causing integration tests to
pass when they should not.

I answered a similar question on stackoverflow a while back that goes
a little more in depth:
http://stackoverflow.com/questions/145131/whats-the-best-strategy-for-unit-testing-database-driven-applications/145163#145163

-Mark