How can I write a unit test to check the http status code when HttpException is thrown?

I am coding an API client, which should throw a System.Web.HttpException with the appropriate HTTP status code when the request is not successful. I know that I can test that HttpException is thrown by using the [ExpectedException(typeof(HttpException))] attribute, but this won't tell me that the status code was correct. How can I assert that the status code is correct?

Here is my client:

public static async Task<HttpResponseMessage> SubmitRequest(string endPoint, string apiKey)
{
    ServerResponse serverMessage = new ServerResponse();
    var credentials = Convert.ToBase64String(Encoding.ASCII.GetBytes(String.Format( "{0}:", apiKey)));

    using (var client = new HttpClient())
    {
        client.BaseAddress = new Uri("https://localhost/api/v1/");
        client.DefaultRequestHeaders.Accept.Clear();
        client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
        client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue( "Basic", credentials );

        // HTTP GET
        HttpResponseMessage response = await client.GetAsync(endPoint);
        // if response status code is in the range 200-299
        if (response.IsSuccessStatusCode)
        {
            return response;
        }

        // request was not successful
        if (response.StatusCode == HttpStatusCode.Unauthorized)
        {
            throw new HttpException(401, "Not authorized.");
        }
    }
}