public void ShouldBeAbleToUpdateUsersFirstName() { InMemoryStorage storage = new InMemoryStorage(); int testedUserdId = 5; string testedFirstName = "test"; UserModel testUser = new UserModel { Id = testedUserdId, FirstName = testedFirstName, LastName = "", Birthdate = DateTime.Now }; var result = storage.UpdateUser(testUser); var changedUser = storage.GetUsersList().FirstOrDefault(x => x.Id == testedUserdId); Assert.True(result); Assert.NotNull(changedUser); Assert.Equal(changedUser.FirstName, testedFirstName); }