public void GetModelIdsByMakeId_ShouldReturnNeededItems() { int id = 2; var items = new List <Vehicle>() { new Vehicle() { MakeId = id, ModelId = 1, BodyTypeId = 10 }, new Vehicle() { MakeId = id, ModelId = 1, BodyTypeId = 3, Id = 1 }, new Vehicle() { MakeId = id, ModelId = 2, BodyTypeId = id, Id = 2 }, new Vehicle() { MakeId = id, ModelId = 3, BodyTypeId = id }, }.AsQueryable(); var repositoryMock = new Mock <IInternalDbRepository <Vehicle> >(); repositoryMock.Setup(x => x.All()).Returns(() => items); var service = new VehiclesService(repositoryMock.Object); var response = service.GetModelIdsByMakeId(id); Assert.AreEqual(response.Count, 3); Assert.AreEqual(response[0], 1); Assert.AreEqual(response[1], 2); Assert.AreEqual(response[2], 3); repositoryMock.VerifyAll(); }