BrowsR helper for integration testing in ASP.NET 5

Dominick and I were working together on some unit tests for an ASP.NET 5 project. These tests were integration tests so we used the the TestServer from ASP.NET 5 TestHost project to load an entire ASP.NET pipeline. This allows you to use HttpClient to make HTTP calls into the running server. The main problem we had was that we needed to simulate a browser client that could hold onto cookies and follow redirects, so based upon Damian Hickey’s excellent OwinMessageHandler, we crufted up this for ASP.NET 5 (and of course had to give it a witty name):

public class BrowsR : DelegatingHandler
{
    private CookieContainer _cookieContainer = new CookieContainer();

    public bool AllowAutoRedirect { get; set; } = true;
    public bool AllowCookies { get; set; } = true;
    public int AutoRedirectLimit { get; set; } = 20;

    public BrowsR(HttpMessageHandler next)
        : base(next)
    {
    }

    protected async override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
    {
        var response = await SendCookiesAsync(request, cancellationToken);

        int redirectCount = 0;

        while (AllowAutoRedirect && (
                response.StatusCode == HttpStatusCode.Moved
                || response.StatusCode == HttpStatusCode.Found))
        {
            if (redirectCount >= AutoRedirectLimit)
            {
                throw new InvalidOperationException(string.Format("Too many redirects. Limit = {0}", redirectCount));
            }
            var location = response.Headers.Location;
            if (!location.IsAbsoluteUri)
            {
                location = new Uri(response.RequestMessage.RequestUri, location);
            }

            request = new HttpRequestMessage(HttpMethod.Get, location);

            response = await SendCookiesAsync(request, cancellationToken).ConfigureAwait(false);

            redirectCount++;
        }
        return response;
    }

    protected async Task<HttpResponseMessage> SendCookiesAsync(HttpRequestMessage request, CancellationToken cancellationToken)
    {
        if (AllowCookies)
        {
            string cookieHeader = _cookieContainer.GetCookieHeader(request.RequestUri);
            if (!string.IsNullOrEmpty(cookieHeader))
            {
                request.Headers.Add("Cookie", cookieHeader);
            }
        }

        var response = await base.SendAsync(request, cancellationToken);

        if (AllowCookies && response.Headers.Contains("Set-Cookie"))
        {
            var responseCookieHeader = string.Join(",", response.Headers.GetValues("Set-Cookie"));
            _cookieContainer.SetCookies(request.RequestUri, responseCookieHeader);
        }

        return response;
    }
}

public class Startup
{
    public void ConfigureServices(IServiceCollection services)
    {
        // ...
    }

    public void Configure(IApplicationBuilder app)
    {
        // ...
    }
}

To use it, then you’d do something like this:

var startup = new Startup();
var server = TestServer.Create(null, _startup.Configure, startup.ConfigureServices);
var handler = server.CreateHandler();
var client = new HttpClient(new BrowsR(handler));
var result = await client.GetAsync("...");

The requests will now follow redirects and hold onto cookies across those redirects. Too bad this isn’t built into the ASP.NET TestHost itself.

Enjoy.