Question

I have the following contract which gets an injected property at runtime:

public interface IBroker
{
   IDriver Driver { get; }
}

public interface IDriver
{
   void Save();
}

public class FileDriver : IDriver { }
public class SqlDriver : IDriver { }

I am preparing my mocks in one shot because the test fitness is pretty big, and I am preparing two versions of my broker in the following way:

var mockFileBroker = new Mock<IBroker>();
mockFileBroker.Setup(x => x.Driver).Returns(new FileDriver());

var mockSqlBroker = new Mock<IBroker>();
mockSqlBroker.Setup(x => x.Driver).Returns(new SqlDriver());

The problem is that when I investigate the property Driver it is always of type SqlDriver for both mocks … so it looks like Moq is always resolving the contract IDriver using the latest registration …
Is there anything I can do to avoid this behavior?

Answer 1

Moq will return the latest registration, but only on the same object.

Double check you are not using the wrong broker somewhere, or that you have missed a mock somewhere and production code is re-setting your Driver.

Patrick Steele makes a good point that you should also consider mocking the returned IDriver too, especially as unit tests should typically avoid using the file system and databases.