public void ValidateAndRegisterUserIfNotExisting_WithNonExistingUser_ShouldRegisterUser() { // Arrange . const string email = "*****@*****.**"; var name = new Tuple <string, string>("Ananth", "Tatachar"); var userName = $"{name.Item1} {name.Item2}"; _userInfoProvider.GetFirstAndLastNames(userName) .ReturnsForAnyArgs(name); _userInfoProvider.GetUser(name, email).ReturnsNullForAnyArgs(); // Act . _target.ValidateAndRegisterUserIfNotExist($"{name.Item1} {name.Item2}", email); // Assert . _userInfoProvider.Received().RegisterUser(name, email); }