Matthias Noback: Test-driving repository classes - Part 1: Queries

Matthias Noback has kicked off a new series of posts on his site covering the use of the repository design pattern in different situations. In this first post he focuses on "test driving" classes for handing database queries and their results.

A test for a repository can't be a unit test; that wouldn't make sense. You'd leave a lot of assumptions untested. So, no mocking is allowed.

[...] But how do you test everything that is going on in a repository? Well, I found out a nice way of doing so, one that even allows you to use some kind of test-driven approach. In this article I'll cover one of the two main use cases for repositories: querying the database, and returning some objects for it. The other use case - storing and loading objects - will be discussed in another article.

He starts by getting everyone on the same page with a definition of a "query" and how it relates back to a repository class. He then walks through the process of how to test the class, first as a general "get all" query then with a check on the "active" state. Once the test goes green (successful), he adds more variations to both the tests and fixtures. There's not a lot of code examples in this post but it does show some good concepts to get you headed down the right path.