public async Task GetUserPreviousAdministrations_Valid_Test() { // Arrange _cityParticipantsService .Setup(c => c.GetPreviousAdministrationsOfUserAsync(It.IsAny <string>())) .ReturnsAsync(It.IsAny <IEnumerable <CityAdministrationDTO> >()); CitiesController citycon = CreateCityController; // Act var result = await citycon.GetUserPreviousAdministrations(GetStringFakeId()); // Assert Assert.NotNull(result); Assert.IsInstanceOf <OkObjectResult>(result); }