Mock Alamofire and URLSession requests without touching your code implementation

Follow up on https://github.com/WeTransfer/Mocker/issues/88 and https://github.com/WeTransfer/Mocker/issues/89

https://github.com/WeTransfer/Mocker/issues/89 actually resolved the build-time issue but it actually crashes the app during runtime.

I tried importing XCTest.framework in my project (embed & sign, embed without signing, do not embed), but none of these options worked for me.

Sometimes you want the same URL to return different results at different times during a test - for example, an error payload first and then a success payload.

Dynamic Mock support enables this by allowing one to setup a closure (onMockFor) that gets called as a first step in mock matching (in Mocker's mock(for request: URLRequest) -> Mock?). If this closure returns a Mock, that is the mock returned from mock(for …) and is used to fulfill the mocked network request.

The particular use case I had was for a service call made with an expired token. The networking layer in this app will catch the expired token error, automatically make a refresh token service call, and then auto-retry the original service call.

In this situation I needed to have the mock for the original service call return a 401 for the expired token as long as the currentToken doesn't match the newGoodToken returned by the mocked refresh token call (which is auto-saved into currentToken by the networking layer).

So my (simplified) onMockFor will look something like this:

let refreshMock = Mock(url: refreshURL, dataType: .json, statusCode: 200, data: [.get: goodRefreshTokenData])
refreshMock.register()
let failureMock = Mock(url: serviceURL, dataType: .json, statusCode: 401, data: [.get, Data()])
failureMock.register()

let successMock = Mock(url: serviceURL, dataType: .json, statusCode: 200, data: [.get: goodMockData])
// Note: do not register! Will overwrite failureMock (same URL).

// Then add the `onMockFor` closure to check if we have the new token
Mocker.onMockFor = { (request: URLRequest) -> Mock? in
  guard request.url == serviceURL else { return nil }
  if currentToken == newGoodToken {
      return successMock
  }
  return nil
}

Seemed like it might be useful to others, and I'd rather not maintain our own custom fork of Mocker separate from yours, so I thought I'd open a PR for this feature in case you'd like to incorporate it in Mocker proper. Tried to stick to your format and style and the majority of the code added is tests. Happy to change things to make it work better for you.

Hello, This is my first time contribution ever. Yesterday I wrote a question / feature request for our needs: https://github.com/WeTransfer/Mocker/issues/83

After checking out the source, I found an easy way to integrate this feature without changing the current way it works. So I propose a Pull request to integrate it.

This feature adds a new property to the Mocker struct called mode. By default the current mode is .optout meaning you have to manually define all the routes you want the system to ignore and thus to process as if the mocker does not exist. This is the way it works today. The other mode is .optin used to let all the routes being processed as if there were no mocking system, except for the mocked routes.

The use case leading to this feature is when you have an existing API with many routes, and a team has to develop a new route, for your development phase, you can mock only this route, to keep using you app and all the other routes in a complete transparent way.

I hope you'll find this useful.

I didn't see any clear means of returning a failed network interaction (no route to host, for example) with Mocker, but I wanted that for some testing of my own.

I've made a slight modification in a forked version that has an additional initializer ('reportFailure' - a boolean) that will return throw exception on URL access instead of returning Data & a response code. Is this something you'd like as a pull request?

I wanted to offer, but wasn't sure how/if you wanted contributions to this library. I'm using it a bit differently than it was originally designed - more for testing failure scenarios, but it served me pretty well where I needed it: forked variant at https://github.com/heckj/swiftui-notes/blob/master/UsingCombineTests/Mock.swift

I'm having trouble matching a mock I create with the corresponding actual request being generated from an Alamofire requst, where the url, headers and method all match.

Here's my mock setup:

public final class MockedSeriesData {
    public static let exampleJSON: URL = Bundle(for: MockedSeriesData.self).url(forResource: "exampleSeriesList", withExtension: "json")!
}

class SeriesSupportTests: XCTestCase {
        let configuration = URLSessionConfiguration.default
        configuration.protocolClasses = [MockingURLProtocol.self]
        let sessionManager = SessionManager(configuration: configuration)
        
        let originalURL = SeriesSupport.getSeriesListURL()
        let expectation = self.expectation(description: "getAllSeries()")
        
        if let url = originalURL {
            print("Mock URL: \(url)")
            print("Mock URL (absolute): \(url.absoluteString)")
            let mock = Mock(url: url, contentType: .json, statusCode: 200, data: [
                .get : MockedSeriesData.exampleJSON.data 
            ])
            Mocker.register(mock)
            SeriesSupport.getAllSeries(sessionManager: sessionManager, oktaHelper: oktaHelper) { seriesOption, errorOption in
                expectation.fulfill()
                // Evaluate result of completionHandler 
        } else {
            XCTFail( "Unable to unwrap Series List URL" )
        }
        
        waitForExpectations(timeout: 10) { error in
            if let error = error {
                print("Error: \(error.localizedDescription)")
            }
        }
    }
}

• I thought maybe I was failing because my headers weren’t matching, so I removed the headers and still wasn’t getting a match.
• I replaced our actual endpoint with , but I have validated it is exactly the same in all print statements

Here’s the real actual Alamofire request:

static let PODCAST_SERVICE_BASE_URL_PREFIX = "https://<host>/dev/podcast/"
    static let SERIES_SERVICE_ENDPOINT_SUFFIX = "series"

    class func getSeriesListURL() -> URL? {
        return URL(string: SERIES_SERVICE_ENDPOINT_SUFFIX, relativeTo: URL(string: PODCAST_SERVICE_BASE_URL_PREFIX))
    }

    class func getAllSeries( sessionManager: Alamofire.SessionManager=Alamofire.SessionManager.default, oktaHelper: OktaAuthSupport=OktaAuthHelper() ) {
        if let url = getSeriesListURL() {
            print("URL: \(url)")
            print("URL (absolute): \(url.absoluteString)")
            sessionManager.request(url, method: .get, headers: HTTPHeaders()).responseJSON { response in
                switch response.result {
                case .success(let value):
                    let json = JSON(value)
                    print("JSON: \(json)")
                    // Convert JSON to array and call completion handler with array
                case .failure(let error):
                    print(error)
                    // Call completion handler with error
                }
            }
        }
    }

What is getting printed:

Mock URL: series -- https://<host>/dev/podcast/
Mock URL (absolute): https://<host>/dev/podcast/series

URL: series -- https://<host>/dev/podcast/
URL (absolute): https://<host>/dev/podcast/series

And the error I get from Mocker:

com.apple.CFNetwork.CustomProtocols (10): Fatal error: No mocked data found for url Optional("https://<host>/dev/podcast/series") method Optional("GET"). Did you forget to use register()?

If I step into the Mocker code, I see my mock registered, but I can't step into the == check where it is evaluating a match on the request to see what is actually getting compared.

Any help would be greatly appreciated!

Frank

As you know, top level collection objects are also valid JSON. But, Mocker wasn't support them because of the casting that made up in the MockingURLProtocol.swift

I want to test our error handling and was hoping to use Mocker for it. We use Alamofire (but the bug is reproducible with URLSession).

Without Alamofire (pseudo code)

                    var url: URL!
                    var urlSession: URLSession!

                    beforeEach {
                        let configuration = URLSessionConfiguration.default
                        configuration.protocolClasses = [MockingURLProtocol.self]
                        urlSession = URLSession(configuration: configuration)

                        let error = ResponseError.testError
                        url = URL(string: "https://test.mycompany.com/thisisvalid?key=hello")!
                                                
                        mock = Mock(url: url, ignoreQuery: true, dataType: .json, statusCode: 404, data: [.get: Data()], requestError: error)
                        mock.register()
                    }

                    it("should call completion with correct error") {
                        waitUntil(timeout: .seconds(2)) { done in
                            urlSession.dataTask(with: url) { (data, response, error) in
                                debugPrint("this error is: \(error as Optional)")

// assertions on actions based on error
                                done()
                            }.resume()
                        }
                    }

po error

ResponseError Code=0 "(null)" UserInfo={_NSURLErrorRelatedURLSessionTaskErrorKey=(
    "LocalDataTask <xxxx>.<1>"
), _NSURLErrorFailingURLSessionTaskErrorKey=LocalDataTask <xxxx>.<1>}

^ this should have been the error I passed but instead I received a .sessionTaskFailed error.

I did spend some time looking into this and the finishRequest inside MockingURLProtocol does get the mock.requestError properly but from there i'm not sure where it goes.

In the actual project i'm using Alamofire but there too i'm getting similar error. The requestError in that case was let error: AFError = AFError.responseValidationFailed(reason: .unacceptableStatusCode(code: 404)).

the returned error is

▿ Optional<Error>
  - some : Error Domain=Alamofire.AFError Code=9 "(null)" UserInfo={_NSURLErrorRelatedURLSessionTaskErrorKey=(
    "LocalDataTask <xxxx>
), _NSURLErrorFailingURLSessionTaskErrorKey=LocalDataTask <xxxx>

These extra imports allow to use the library in tests on Linux. As an example I've enabled Linux tests in kean/Get library.

Also, removed unrelated warning that swift build showed:

Mocker.swift:79:21: warning: result of call to 'registerClass' is unused
        URLProtocol.registerClass(MockingURLProtocol.self)
                    ^            ~~~~~~~~~~~~~~~~~~~~~~~~~

Resolves #94

Not requiring this weakly means it'll attempt to load on every run; but XCTest will not be available when running the application directly.

What did I do to test this?

• run pod spec lint Mocker.podspec to verify the podspec passes validation

 -> Mocker (2.5.3)
    - NOTE  | xcodebuild:  note: Using new build system
    - NOTE  | xcodebuild:  note: Building targets in parallel
    - NOTE  | xcodebuild:  note: Using codesigning identity override: -
    - NOTE  | xcodebuild:  note: Build preparation complete
    - NOTE  | [iOS] xcodebuild:  note: Planning build
    - NOTE  | [iOS] xcodebuild:  note: Analyzing workspace
    - NOTE  | [iOS] xcodebuild:  note: Constructing build description
    - NOTE  | [iOS] xcodebuild:  warning: Skipping code signing because the target does not have an Info.plist file and one is not being generated automatically. (in target 'App' from project 'App')

Analyzed 1 podspec.

Mocker.podspec passed validation.

• integrated the local build into a new project using

pod 'Mocker', :path => '~/Path/To/Mocker.podspec'

• verified that this does not crash at runtime
• verified that this does not crash when importing Mocker, and using its APIs in a test bundle
• verified that XCTest is no longer "always" required in the linked frameworks and libraries that CocoaPods generates.

Using specific assert functions will generate easier to understand failure messages if the tests were to fail. For example, in the XCTAssertNil case, it will say "something was unexpectedly not nil" instead of only "test failed".

As discussed in https://github.com/WeTransfer/Mocker/issues/134

I've also added an additional initializer to simplify the mock creation in case a single non-get request has to be mocked.

Hey 👋

I constantly see Mocker warnings about not mocking 3rd party URLs such as from mixpanel or Realm. The problem is that the URLs look like:

https://api.mixpanel.com/track/?data=eyJldmVudCI………redacted-for-brevity-but-it's-a-really-long-url-jBkYmQ3ODzeCJ9fQ==&ip=1

https://static.realm.io/update/cocoa?x.y.z // where x.y.z is my Realm library version

Thus I thought if I called:

Mocker.ignore(URL(string: "https://static.realm.io")!)

That Mocker would ignore all requests within this domain, but it doesn't.

I'd like to be able to ignore calls to realm.io or mixpanel.com (perhaps even omitting static. or api. for instance), or at least https://static.realm.io and https://api.mixpanel.com.

I'm aware of a function to ignore all URLs but really doesn't accomplish the goal because I like the warnings for all requests that are from my own application.

What are the challenges around implementing this? Are there any risks?

Appreciate all the help!