How to figure out the the URL when 'No matching mock handler' exception occurs?

[Jericho]

I'm getting a No matching mock handler in my unit test which is most likely caused by a typo in my expectation:

var mockHttp = new MockHttpMessageHandler();
mockHttp.Expect(HttpMethod.Get, "...the url...").Respond("application/json", "...the response...");

but I can't figure out what I typed wrong. Is there any way to get the actual URL?

[Jericho]

I added a fallback like so:

var fiddlerProxy = new WebProxy("http://localhost:8888");
var handler = new HttpClientHandler { Proxy = fiddlerProxy, UseProxy = true };
mockHttp.Fallback.Respond(new HttpClient(handler));

which allowed me to see the request in Fiddler and figure out my typo but still, I'm curious if there's a simpler way to achieve this that wouldn't involve using a third party tool.

[richardszalay]

If you have access to the error No matching mock handler then you should have access to the HttpResponseMessage, in which case you can just access the url via response.RequestMessage.RequestUri.

You could even configure fallback to include that URI in the response message:

// eg. No matching mock handler found for "GET http://localhost/abc"
mockHttp.Fallback.Response(req => new HttpResponseMessage(System.Net.HttpStatusCode.NotFound)
{
  ReasonPhrase = $"No matching mock handler found for \"{req.Method.ToString().ToUpperInvariant()} {req.RequestUri.AbsoluteUri}\""
});

[Jericho]

Excellent suggestion! In fact, I suggest this should be the built-in behavior.