What would you put into the unit test of a repository class (data access layer)?

I'd like to write a unit test for my data access layer to make sure that everything works allright in it. The question is, what kind of things should I put into the tests?

The DAL is a static Repository class which hides the underlying layer (Fluent NHibernate) and exposes stuff to the public through an IQueryable.

I thought about

• CRUD (Create/Retrieve/Update/Delete) operations
• Transactions

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Is there anything else about a DAL that is worth testing?

Thanks in advance for your answers!

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Repository implementation is tested with integration tests, not unit tests. Isolating repository implementation (mocking ORM) is almost impossible. Please take a look at this answer. Integration test uses a real ORM combined with real or fake (usually in-memory) database to do following:

• saving new object
• change -> persist -> restore sequence
• all 'Find' methods

Essentially you testing the correctness of:

• mappings (even if you use fluent)
• criteria
• hql or sql queries

Transactions are usually handled by an application layer, not repositories. You might be interested in this answer. Encapsulating IQueryable in the repository implementation will make testing a lot easier for you.

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1. Need to test proper Exception handling
2. Time Out Parameter of Database Connection
3. Time Out Parameter of Store Procedure invocation
4. Proper input parameters mapping . If store procedure expects to receive float but receive int.

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Usually in a DAL you don't have business logic, just plain db access code which is probably 1-5 lines long, so there is not to much to test ...

If you are sure you want to unit test it then i believe CRUD is fine. Mock out NHibernate, provide fake data and test against that fake data ;).

Hope this helps ;)