GetTokenByPinRequest() private method

/// Thrown when a null reference is passed to a method that does not accept it as a /// valid argument. ///
private GetTokenByPinRequest ( string url, string pin, string clientId, string clientSecret ) : HttpRequestMessage
url string
pin string
clientId string
clientSecret string
return System.Net.Http.HttpRequestMessage
        public void GetTokenByPinRequest_WithClientIdNull_ThrowsArgumentNullException()
        {
            var requestBuilder = new OAuth2RequestBuilder();

            var exception =
                Record.Exception(() => requestBuilder.GetTokenByPinRequest("url", "123", null, "clientSecret"));
            Assert.NotNull(exception);
            Assert.IsType<ArgumentNullException>(exception);

            var argNullException = (ArgumentNullException) exception;
            Assert.Equal(argNullException.ParamName, "clientId");
        }
        public async Task GetTokenByPinRequest_WithPinEqual()
        {
            var requestBuilder = new OAuth2RequestBuilder();

            var request = requestBuilder.GetTokenByPinRequest("https://api.imgur.com/oauth2/token", "4899", "123",
                "1234");

            Assert.NotNull(request);
            Assert.Equal("https://api.imgur.com/oauth2/token", request.RequestUri.ToString());
            Assert.Equal(HttpMethod.Post, request.Method);
            Assert.NotNull(request.Content);

            var expected = await request.Content.ReadAsStringAsync().ConfigureAwait(false);

            Assert.Equal("client_id=123&client_secret=1234&grant_type=pin&pin=4899", expected);
        }