public Task SendFileWhenFileNotFoundThrows()
 {
     var response = new DefaultHttpContext().Response;
     return Assert.ThrowsAsync<FileNotFoundException>(() => response.SendFileAsync("foo"));
 }
 public Task SendFileWhenNotSupported()
 {
     var response = new DefaultHttpContext().Response;
     return Assert.ThrowsAsync<NotSupportedException>(() => response.SendFileAsync("foo"));
 }