Entity Framework (code first) in memory database for unit testing

Question

For unit testing purposes, is it possible to do this:

Have test data in some format (XML?) checked into source control
When unit tests are run, instantiate some kind of in memory database from this test data
Have EF run against this in memory database for the duration of the unit test run

?

We don't want our unit tests to rely on a specific external database being present, and in a specific state.

We also don't want to maintain two different "worlds" in our code and tests, the real world where EF runs against a real db and a fake work where our tests run against some kind of EF mock.

I see contradiction. You don't want to use real database and you don't want to use fake. So what do you want to use? — Piotr Perak
– Piotr Perak, Commented Aug 15, 2012 at 12:42
he wants to use a blank in memory database for the tests, that is real from EF:s perspective, but not persistent between test runs and tests are not dependant on an external database server. — eatfrog
– eatfrog, Commented Sep 13, 2012 at 11:37

Ladislav Mrnka · Accepted Answer · 2012-08-15 12:06:47Z

6

Unit tests should not be dependent on any database. Any dependency on database (even in memory database) means you are doing integration tests and integration tests should be done against the real database you are going to use.

I'm not aware of any XML database for EF but even if it exists you are back in front of your requirement: We also don't want to maintain two different "worlds" in our code and test. Every database has its own EF provider created by different company. Even providers for MS SQL Server and MS SQL Server Compact Edition are different enough to make switching between them quite challenging.

What you should do:

Hide all EF usage behind some abstraction (that includes everything including Linq-to-entities queries) and mock this abstraction instead of EF for unit tests
Use integration tests against the real database implementation you want to use in production for testing the abstraction itself

answered Aug 15, 2012 at 12:06

Ladislav Mrnka

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1 Comment

Piotr Perak Over a year ago

So are you suggesting creating another repository? I see mostly problems with repositories trying to hide EF or other ORM's. DbContext (implementing IDbContext) is already a repository.

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