Using
Fiddler Core
web proxy

5 minute presentation by Tim

Why?

avoid hitting live APIs
control API responses
rerunnable unit tests
test edge cases / unexpected responses

no need to change production code
no need to abstract an interface for dependency injection

Fiddler

http://www.fiddler2.com/fiddler2/

"Fiddler...":

is a Web Debugging Proxy which logs HTTP(S) traffic; 
allows you to "fiddle" with incoming or outgoing data;
can be extended using any .NET language; 
is freeware; 
can debug traffic from IE, Chrome, Safari, Firefox, Opera, Windows Phone, iPod/iPad, ..., etc. 

Fiddler Core dlls

http://www.fiddler2.com/fiddler/Core/

MockWebProxyHelper

https://gist.github.com/4079321
public static class MockWebProxyHelper
{
  public static void SetUp() {...}
  public static void TearDown() {...}

  public class Response
  {
    public string Header { get; set; } // default "HTTP/1.1 200 OK"
    public string Body { get; set; } // default ""
  }
  public static Func<HttpMethods, string, Response> GetMockResponse
    = delegate { return new Response(); };
}

Set up & Tear down

[TestFixture]
public class StockCheckClientBackgroundWorkerTests
{
    [TestFixtureSetUp]
    public void StartFiddlerProxy()
    {
        MockWebProxyHelper.SetUp();
    }

    [TestFixtureTearDown]
    public void StopFiddlerProxy()
    {
        MockWebProxyHelper.TearDown();
    }

Mock response

[Test]
public void TestMockClientCall()
{
  MockWebProxyHelper.GetMockResponse = (httpMethod, url) =>
    new MockWebProxyHelper.Response(body: 
      @"{'productCount':1,
         'products':[
           {'productId':'1012881',
            'categoryId':
            'CAT13617200330',
            'availableStock':'23'}
         ]}");

  // dummy key - should work anyways, cos it's a mock!
  var client = new StockCheckClient {AuthKey = "dummy-auth-key"};

  List<Product> inStockProducts =
    client.GetCategoryItemsInStock("CAT13617200330");
  Assert.AreEqual(1, inStockProducts.Count);
  Assert.AreEqual(23, inStockProducts[0].AvailableStock);
}

Possible uses

  1. Dummy response files
  2. Return actual data
  3. Fake "chaos monkey"
  4. more?

Dummy response files

eg http://myapi.com/products?categoryId=CAT13617200330
filename "GET myapi_com_products_categoryId_CAT13617200330.txt":
HTTP/1.1 200 OK
{'productCount':1,'products':[{'productId':'1012881','categoryId':'CAT13617200330','availableStock':'23'}]}
[TestFixtureSetUp]
public void StartFiddlerProxy()
{
  MockWebProxyHelper.SetUp();
  MockWebProxyHelper.GetMockResponse = (httpMethod, url) =>
  {
    var file = url.Replace("http://", "")
      .Replace('/', '_').Replace('?', '_').Replace('=', '_');
    var lines = File.ReadAllLines(httpMethod + " " + file +".txt");
    return new MockWebProxyHelper.Response(
      header: lines.First(),
      body: String.Join(Environment.NewLine, lines.Skip(1)));
  }
}

Return actual data

MockWebProxyHelper.GetMockResponse =
  (httpMethod, url) =>
  {
    // eg http://myapi.com/products?categoryId=CAT13617200330
    var categoryId = url.Split('=').Last();
    var products =
      productsRepository.Where(x => x.CategoryId == categoryId);

    var body = JsonConvert.SerializeObject(responseObject));
    return new MockWebProxyHelper.Response(body: body);
  };

Fake "chaos monkey"

Return whole gamut of HTTP status codes, to ensure your client code handles errors correctly

// TODO:

Record mode

If a dummy response doesn't exist, run a real request and record the response as a dummy for next time.

MOAR?

The End.

Made with Slides.com