April 28 2014

Moq - Get Setup() to return a dynamic collection from a fake repository

Use Moq lazy loading to return an updated collection from the Setup() method, it's as easy as changing the argument to the Setup().Returns() method from an object to a lambda expression.

So if you've got this:

_mockUserRepository.Setup(x => x.GetAll()).Returns(FakeUserData.Users);

Just change it to this:

_mockUserRepository.Setup(x => x.GetAll()).Returns(() => FakeUserData.Users);

 

If you are using this approach you also need to remember to reset your fake data at the beginning of each test, I do this with a simple static reset method on my fake data class.

class FakeUserData
{
    public static void Reset()
    {
        _users = null;
    }

    ...
}

Which is called before each test with the following setup method (using MSTest):

[TestInitialize]
public void Setup()
{
    FakeUserData.Reset();

    ...
}

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