public void NotFoundTwiceForSameHost_CouldNotDownloadExceptionMessage()
{
var host = "flaky404.githubusercontent.com";
var url = new Uri("https://" + host + "/u/00000000?v=4");
var expectMessage = ImageDownloader.CouldNotDownloadExceptionMessage(url);
var httpClient = Substitute.For <IHttpClient>();
var response = Substitute.For <IResponse>();
response.StatusCode.Returns(HttpStatusCode.NotFound);
httpClient.Send(null, default(CancellationToken)).ReturnsForAnyArgs(Task.FromResult(response));
var target = new ImageDownloader(new Lazy <IHttpClient>(() => httpClient));
var ex1 = Assert.CatchAsync <HttpRequestException>(async() => await target.DownloadImageBytes(url));
var ex2 = Assert.CatchAsync <HttpRequestException>(async() => await target.DownloadImageBytes(url));
Assert.That(ex1?.Message, Is.EqualTo(expectMessage));
Assert.That(ex2?.Message, Is.EqualTo(expectMessage));
}