NSURLSession-Mock 1.1.0

NSURLSession-Mock 1.1.0

LangLanguage SwiftSwift
License Custom
ReleasedLast Release Apr 2017
SwiftSwift Version 3.0
SPMSupports SPM

Maintained by Sam Dean, Sam Dean.

  • By
  • Sam Dean




This pod is designed to help during functional testing by returning canned responses to URLs requested by the app.


To mock a single request use mockNext - this method can be called multiple times and the responses will be returned in the same order they were added in:

let body1 = "Test response 1".data(using: String.Encoding.utf8)!
let body2 = "Test response 2".data(using: String.Encoding.utf8)!

let url = URL(string: "https://www.example.com/1")!
let request = URLRequest(url: url)

// Mock calls to that request returning both responses in turn
_ = URLSession.mockNext(request: request, body: body1, delay: 1)
_ = URLSession.mockNext(request: request, body: body2, delay: 1)

To mock every call to a request, just use mockEvery instead:

URLSession.mockEvery(request: request, body: body, delay: 1)

The parameters body and delay are optional if you want you code to be a bit more succinct. i.e. to just return 200 with no data you can do:

URLSession.mockEvery(request: request)

Ephemeral mocks have priority over permanent mocks. This is to say that, if you were to add permanent and ephemeral mocks for the same request, the ephemeral mocks would be returned and consumed first.

If you want your response to depend on the URL called, you can pass in a function like this:

let expression = "https://www.example.com/product/([0-9]{6})"

// Return a valid test product JSON response with the correct pid
URLSession.mockEvery(expression: expression) { (matches:[String]) in
    let pid = matches.first!
    let body = "{ 'productId':'\(pid)', 'description':'This is a test product' }".data(using: String.Encoding.utf8)!
    return .success(statusCode: 200, headers: [:], body: body)

If you want to mock errors (internal ios error, not server errors; they are just responses with statusCode: 500) you can return a .Failure instead

let expression = "https://www.example.com/some_url.json"

// Return a valid test product JSON response with the correct pid
URLSession.mockEvery(expression: expression) { (matches:[String]) in
    let error = NSError(domain: "TestNetworkingLayerError", code: 0, userInfo: [NSLocalisedDescriptionKey: "Could not open session blah blah something"])
    return .failure(error)

To remove all the mocks (or just some of them) you can do

// Remove everything

// Remove all mocks matching a request
NSURLSession.removeAllMocks(of: request)

If you would like to fail requests that haven’t been mocked, set the NSURLSession’s request evaluator to return whether or not the requests must be allowed. For example, to ensure that all calls to Net-A-Porter’s domain are mocked you would:

NSURLSession.requestEvaluator = { request in
    guard let url = request.URL else { return .reject }

    return url.host == "www.net-a-porter.com" ? .reject : .passThrough

If a request to www.net-a-porter.com is made and not mocked, an exception will be raised.


This pod is designed to be AFNetworking (~>2.0) friendly - mocks to NSURLSession will work via AFNetworking’s AFHTTPSessionManager methods. Checkout AFNetworkingTests.swift for an example.

Example project

To run the example project, clone the repo, and run pod install from the Example directory first. This project contains a test suite that should show examples of how to use the pod.


NSURLSession-Mock is available through CocoaPods. To install it, simply add the following line to your Podfile:

pod "NSURLSession-Mock"


Sam Dean, [email protected]


NSURLSession-Mock is available under the Apache license. See the LICENSE file for more info.