Mock service locator provider from http://joseoncode.com/2010/02/24/testing-code-that-use-servicelocator-servicelocatorstub/

ServiceLocatorStub.cs

public class ServiceLocatorStub : ServiceLocatorImplBase 
{
    private readonly IDictionary<Type, ICollection<object>> 
        registeredTypes = new Dictionary<Type, ICollection<object>>();

    private ServiceLocatorStub()
    {}

    public ServiceLocatorStub AddInstance<TService>(TService instance)
    {
        ICollection<object> instanceCollection;
        if(!registeredTypes.TryGetValue(typeof(TService), out instanceCollection))
        {
            instanceCollection = new List<object>();
            registeredTypes[typeof (TService)] = instanceCollection;
        }
        instanceCollection.Add(instance);
        return this;
    }

    public static ServiceLocatorStub Create()
    {
        var fakeServiceLocator = new ServiceLocatorStub();
        ServiceLocator.SetLocatorProvider(() => fakeServiceLocator);
        return fakeServiceLocator;
    }

    protected override object DoGetInstance(Type serviceType, string key)
    {
        return registeredTypes[serviceType].FirstOrDefault();
    }

    protected override IEnumerable<object> DoGetAllInstances(Type serviceType)
    {
        return registeredTypes[serviceType];
    }
}