public OAuthTokenService(IHttpClientWrapper httpClient, OAuthTokenServiceConfiguration configuration)
        {
            _httpClient    = httpClient;
            _configuration = configuration;

            _httpClient.AcceptHeaders.Add(new System.Net.Http.Headers.MediaTypeWithQualityHeaderValue("application/vnd.hmrc.1.0+json"));
        }
        public void Arrange()
        {
            _configuration = new OAuthTokenServiceConfiguration
            {
                Url      = "http://unit.test/token",
                ClientId = ClientId
            };

            _clientAcceptHeaders = new List <MediaTypeWithQualityHeaderValue>();
            _httpClient          = new Mock <IHttpClientWrapper>();
            _httpClient.Setup(c => c.AcceptHeaders)
            .Returns(_clientAcceptHeaders);
            _httpClient.Setup(c => c.Post <OAuthTokenResponse>(_configuration.Url, It.IsAny <OAuthTokenRequest>()))
            .ReturnsAsync(new OAuthTokenResponse
            {
                AccessToken  = AccessToken,
                RefreshToken = RefreshToken,
                ExpiresIn    = ExpiresIn,
                Scope        = Scopes,
                TokenType    = TokenType
            });

            _service = new OAuthTokenService(_httpClient.Object, _configuration);
        }