In Castle Windsor 3, override an existing component registration in a unit test

Question

I am attempting to use Castle Windsor in my automated tests like so:

On every test:

• The Setup() function creates a Windsor container, regi

Answer 1

There are two things that you have to do to create an overriding instance:

1. Assign it a unique name
2. Call the IsDefault method

So to get the example to work:

this.WindsorContainer.Register(
                             Component.For<IMediaPlayerProxyFactory>()
                                      .Instance(mockMediaPlayerProxyFactory)
                                      .IsDefault()
                                      .Named("OverridingFactory")
                          );

Because I plan to use this overriding patten in many tests, I've created my own extension method:

public static class TestWindsorExtensions
{
    public static ComponentRegistration<T> OverridesExistingRegistration<T>(this ComponentRegistration<T> componentRegistration) where T : class
    {
        return componentRegistration
                            .Named(Guid.NewGuid().ToString())
                            .IsDefault();
    }
}

Now the example can be simplified to:

this.WindsorContainer.Register(
                             Component.For<IMediaPlayerProxyFactory>()
                                      .Instance(mockMediaPlayerProxyFactory)
                                      .OverridesExistingRegistration()
                          );

---

Later Edit

Version 3.1 introduces the IsFallback method. If I register all my initial components with IsFallback, then any new registrations will automatically override these initial registrations. I would have gone down that path if the functionality was available at the time.

https://github.com/castleproject/Windsor/blob/master/docs/whats-new-3.1.md#fallback-components

Answer 2

Don't reuse your container across tests. Instead, set it to null in the TearDown() and re-initialise it for each actual test.