Reconfigure dependencies when Integration testing ASP.NET Core Web API and EF Core
@ilya-chumakov’s answer is awesome. I just would like to add one more option 3. Use ConfigureTestServices method from WebHostBuilderExtensions. The method ConfigureTestServices is available in the Microsoft.AspNetCore.TestHost version 2.1(on 20.05.2018 it is RC1-final). And it lets us override existing registrations with mocks. The code: _server = new TestServer(new WebHostBuilder() .UseStartup<Startup>() .ConfigureTestServices(services => { services.AddTransient<IFooService, MockService>(); … Read more