public async Task OrderByAddsTheParameterFromBaseType() { // arrange var httpConnection = Substitute.For <IHttpConnection>(); httpConnection .FilterAsync <BiggerTestModel>(Arg.Any <Uri>(), Arg.Any <Dictionary <string, object> >()) .Returns(Task.FromResult(new CollectionResult <BiggerTestModel> { Results = Array.Empty <BiggerTestModel>() })); var apiConnection = new ApiConnection(httpConnection); var client = new TestClient(apiConnection); // act var model = await client.BiggerFilter() .OrderBy(x => x.LastName) .FirstOrDefaultAsync(); // assert _ = httpConnection.Received().FilterAsync <BiggerTestModel>( Arg.Any <Uri>(), Arg.Is <Dictionary <string, object> >(o => o["sort"].Equals("last_name:asc"))); }