Override Autofac registration - Integration tests with DI

Question

I write integration tests for my application, and use my container for this. I want to be able to register all the components as I do in real running, and then override some of the components and switch them to use stubs implementations.

I wouldn't want to seperate the DI and have a container for tests only because I want to test the real thing.

Doing this also seems ugly:

public class MyRegistrations
{
     public static RegisterAll(bool isInTest= false)
     {
           if (isTest) 
           {
             // Register test fakes
            }
            else
                  // Register real components
      }
}

So I thought of overriding registrations in my test enviorment. How should it be done?

Any other better ways for achieving my goal?

Thanks

Answer 1

Autofac will use the last registered component as the default provider of that service

From the AutoFac documation.

In your arrange/setup/testInit phase register the mocks, then resolve the SUT:

[SetUp]
public void TestInit()
{
    Mock<IFoo> mock = new Mock<IFoo>();
    builder.RegisterInstance(mock.object).As<IFoo>();
    ...
    ...
    _target = builder.Resolve<The component>();
}

Note:

Singletons, static members and SingletonLifestyle(registration) may cause some troubles....