public void ValidateFailTest()
 {
     PostCodeValidator target = new PostCodeValidator(); 
     string input = "123456";
     IResult expected = ResultFactory.GetFailResultInstance("Postcode must be 5 digit only.");
     IResult actual;
     actual = target.Validate(input);
     Assert.AreEqual(expected.IsSuccess, actual.IsSuccess);
     
 }
 public void ValidateSuccessTest()
 {
     PostCodeValidator target = new PostCodeValidator(); 
     string input = "12345"; 
     IResult expected = ResultFactory.GetSuccessResultInstance();
     IResult actual;
     actual = target.Validate(input);
     Assert.AreEqual(expected.IsSuccess, actual.IsSuccess);
     
 }
        public async Task Validate_InvalidPostCode_ReturnsInvalidResult()
        {
            var validApiResponse = new PostCodeValidationResponse
            {
                result = false
            };

            SetupHttpClient(validApiResponse);
            _postCodeValidator = new PostCodeValidator(_httpClient, _config);

            var response = await _postCodeValidator.Validate("postCode");

            Assert.IsFalse(response.result);
        }