Unit testing with Moa

Here is how to simulats image download in unit tests instead of sending real network requests.

override func tearDown() {
  super.tearDown()

  MoaSimulator.clear()
}

func testDownload() {
  // Create simulator to catch downloads of the given image
  let simulator = MoaSimulator.simulate("35px.jpg")

  // Download the image
  let imageView = UIImageView()
  imageView.moa.url = "http://site.com/35px.jpg"

  // Check the image download has been requested
  XCTAssertEqual(1, simulator.downloaders.count)
  XCTAssertEqual("http://site.com/35px.jpg", simulator.downloaders[0].url)

  // Simulate server response with the given image
  let bundle = NSBundle(forClass: self.dynamicType)
  let image =  UIImage(named: "35px.jpg", inBundle: bundle, compatibleWithTraitCollection: nil)!
  simulator.respondWithImage(image)

  // Check the image has arrived
  XCTAssertEqual(35, imageView.image!.size.width)
}