DVR Networking tes-ng in Swi/. 

Hi, I'm @soffes. 

DVR is this thing I made when I worked at Venmo. 

Inspired by VCR for Ruby. 

Records networking and plays it back in tests. 

Using DVR 

// Example XCTest func testTimeline() { let expectation = expectationWithDescription("Networking") // Your network client let client = APIClient() client.getTimeline { success in XCTAssertTrue(success) expectation.fulfill() } waitForExpectationsWithTimeout(1, handler: nil) } 

// DVR Session let dvr = Session(cassetteName: "timeline") // Pass into initializer let client = APIClient(session: dir) 

class APIClient { let session: NSURLSession init(session: NSURLSession = NSURLSession.sharedSession()) { self.session = session } } 

func getTimeline(completion: Bool -> Void) { let request = NSURLRequest(URL: timelineURL) session.dataTaskWithRequest(request) { _, _, _ completion(true) }.resume() } 

DVR Internals 

class Session: NSURLSession { let cassetteName: String let backingSession: NSURLSession init(cassetteName: StringbackingSession: NSURLSession = NSURLSession.sharedSession()) { self.cassetteName = cassetteName self.backingSession = backingSession super.init() } override func dataTaskWithRequest(request: NSURLRequest) -> NSURLSessionDataTask { return SessionDataTask(session: self, request: request) } } 

Call resume() & then magic. 

class SessionDataTask: NSURLSessionDataTask { override func resume() { // Playback cassette on disk or record } } 

Casse%es are stored as JSON. 

{ "name" : "example", "interactions" : [ { "recorded_at" : 1434688721.440751, "request" : { "method" : "GET", "url" : "http:\/\/example.com" } "response" : { "body" : "hello", "status" : 200, "url" : "http:\/\/example.com\/", "headers" : { "Cache-Control" : "max-age=604800", "Content-Type" : "text\/plain", "Last-Modified" : "Fri, 09 Aug 2013 23:54:35 GMT", "Content-Length" : "5" } } } ] } 

Why this over mocks? 

Mocks are inherently fragile. You have to couple your tes7ng code with the implementa7on details of your test. — Dave Abrahams, Protocol-Oriented Programming in Swi3 

class DisabledSession: NSURLSession { override func dataTaskWithRequest(request: NSURLRequest, completionHandler: (NSData?, NSURLResponse?, NSError?) -> Void) -> NSURLSessionDataTask? { XCTFail("Networking disabled") return nil } } 

github.com/venmo/DVR 

Thanks