HttpRequestMessageList.cs

public class HttpRequestMessageList : List<HttpRequestMessage>
{
    public void Add(string uri, HttpMethod httpMethod)
    {
        this.Add(new HttpRequestMessage(httpMethod, uri));
    }
}

VerifyRouting.cs

/// <param name="registerWebApiConfigFn">Probably <c>WebApiConfig.Register</c></param>
public static void VerifyRouting(Action<HttpConfiguration> registerWebApiConfigFn,
    HttpRequestMessageList httpRequestMessageList)
{
    var config = new HttpConfiguration();

    registerWebApiConfigFn(config);
    config.EnsureInitialized();


    var stringBuilder = new StringBuilder();
    foreach (var request in httpRequestMessageList)
    {
        stringBuilder.Append(GetRoutingForRequest(request, config));
        stringBuilder.AppendLine();
    }
    Approvals.Verify(stringBuilder.ToString());
}

private static void RemoveOptionalRoutingParameters(IDictionary<string, object> routeValues)
{
    var optionalParams = routeValues
        .Where(x => x.Value == RouteParameter.Optional)
        .Select(x => x.Key)
        .ToList();

    foreach (var key in optionalParams)
    {
        routeValues.Remove(key);
    }
}


private static string GetRoutingForRequest(HttpRequestMessage request, HttpConfiguration config)
{
    StringBuilder stringBuilder = new StringBuilder();
    if (!request.RequestUri.IsAbsoluteUri)
    {
        request.RequestUri =
            new Uri("http://example.com/" + request.RequestUri.OriginalString);
    }
    stringBuilder.AppendLine(request.ToString());

    var routeData = config.Routes.GetRouteData(request);
    if (routeData == null)
    {
        stringBuilder.AppendLine("No route found");
        return stringBuilder.ToString();
    }
    RemoveOptionalRoutingParameters(routeData.Values);
    request.Properties[HttpPropertyKeys.HttpRouteDataKey] = routeData;

    HttpControllerDescriptor httpControllerDescriptor;
    try
    {
        httpControllerDescriptor = new DefaultHttpControllerSelector(config).SelectController(request);
    }
    catch (HttpResponseException ex)
    {
        stringBuilder.AppendLine(string.Format("{0}: {1}", (int)ex.Response.StatusCode, ex.Response.ReasonPhrase));
        return stringBuilder.ToString();
    }
    var controllerContext = new HttpControllerContext(config, routeData, request)
    {
        RouteData = routeData,
        ControllerDescriptor = httpControllerDescriptor
    };
    var actionMapping = new ApiControllerActionSelector().SelectAction(controllerContext);
    stringBuilder.AppendLine(string.Format("Handled By: {0}.{1}",
        actionMapping.ControllerDescriptor.ControllerType.FullName, actionMapping.ActionName));
    return stringBuilder.ToString();
}

VerifyRoutingExample.approved.txt

Method: GET, RequestUri: 'http://example.com/api/Values', Version: 1.1, Content: <null>, Headers:
{
}
Handled By: WebApiGetRouteDataExample.Controllers.ValuesController.Get

Method: PUT, RequestUri: 'http://example.com/api/alues/5', Version: 1.1, Content: <null>, Headers:
{
}
404: Not Found

Method: GET, RequestUri: 'http://example.com/DOESNOTEXIST', Version: 1.1, Content: <null>, Headers:
{
}
No route found

VerifyRoutingTest.cs

[TestMethod]
public void VerifyRoutingTest()
{
    VerifyRouting(WebApiConfig.Register, new HttpRequestMessageList
    {
        {"api/Values", HttpMethod.Get},
        {"api/alues/5", HttpMethod.Put},
        {"DOESNOTEXIST", HttpMethod.Get},
    });
}