单元测试方法，其中扩展方法用于外部资源

Question

I need to Unit test RequestToken method that uses HttpClient and extension method RequestPasswordTokenAsync .

I have got a null reference exception even when a delegatingHandler is passed to the HttpClient .

var delegatingHandler = new DelegatingHandlerStub(false);
var httpClient = new HttpClient(delegatingHandler);

var tokenServices = new TokenServices(httpClient)
tokenServices.RequestToken(passwordTokenRequest);  //exception


 public class TokenServices : ITokenServices
    {
        private readonly HttpClient _httpClient;
        public TokenServices(HttpClient httpClient) 
        {
            _httpClient = httpClient;           
        }

            public async Task<TokenResponse> RequestToken(PasswordTokenRequest request)
        {           

            var response = await _httpClient.RequestPasswordTokenAsync(request);

            }

    }

     public class DelegatingHandlerStub : DelegatingHandler
    {
        private readonly Func<HttpRequestMessage, CancellationToken, Task<HttpResponseMessage>> _handlerFunc;
        public DelegatingHandlerStub(bool toThrowException)
        {
            _handlerFunc = (request, cancellationToken) =>
            {
                if (toThrowException)
                    throw new Exception();

                return Task.FromResult(request.CreateResponse(HttpStatusCode.OK));
            };

        }

        protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
        {
            return _handlerFunc(request, cancellationToken);
        }
    }


namespace IdentityModel.Client
{

    public static class HttpClientTokenRequestExtensions
    {
        public static Task<TokenResponse> RequestPasswordTokenAsync(this HttpMessageInvoker client, PasswordTokenRequest request, CancellationToken cancellationToken = default(CancellationToken));

    }
}           

Answer 1

I have to write a wrapper around HttpClient.

If there are a better solution, please post it here