Replace type in ServiceCollection for testing

replace-service-in-servicecollection.cs

	public static class ServiceExtensions
	{
		public static ServiceCollection ReplaceWithFake<T>(this ServiceCollection services) where T : class
		{
			T fake = Substitute.For<T>();

			var descriptor = new ServiceDescriptor(typeof(T), fake.GetType(), ServiceLifetime.Scoped);
			services.Replace(descriptor);

			return services;
		}
	}
  
// Usage: (install NSubstitute from Nuget)
//services.ReplaceWithFake<ILogger>()
//        .ReplaceWithFake<IRepository>();