How to Unit Test Web API

Mock HttpContext.Current.Request.cs

HttpContext.Current = new HttpContext(new HttpRequest(null, "http://someurl", null), new HttpResponse(new StringWriter()));

UnitTestWebApi.cs

var config = new HttpConfiguration();
var request = new HttpRequestMessage(HttpMethod.Get, "http://host/api/my");
var route = config.Routes.MapHttpRoute("DefaultApi", "api/{controller}/{id}");
var routeData = new HttpRouteData(route, new HttpRouteValueDictionary { { "controller", "my" } });
var controller = new MyController();
controller.ControllerContext = new HttpControllerContext(config, routeData, request);
controller.Request = request;
controller.Request.Properties[HttpPropertyKeys.HttpConfigurationKey] = config;