public void ExistsChecksCorrectly() { //Arrange long addressId = 3; var address = new Address { Id = addressId, CountryId = 1, CityId = 1, StreetId = 1, Building = "test", Apartment = "test" }; var addresses = new List <Address> { address }; var dbSet = addresses.AsQueryable().BuildMockDbSet(); var context = new Mock <hNextDbContext>(new DbContextOptions <hNextDbContext>()); context.Setup(c => c.Set <Address>()).Returns(dbSet.Object); AddressRepository repository = new AddressRepository(context.Object); //Act var found = repository.Exists(new Address { Id = addressId + 1, CountryId = 1, CityId = 1, StreetId = 1, Building = "test", Apartment = "test" }).Result; var notFound = repository.Exists(new Address()).Result; //Assert Assert.AreEqual(found.Id, addressId); Assert.IsNull(notFound); }