Mocker

Mock Alamofire and URLSession requests without touching your code implementation

WeTransfer

769

Swift

Mocker is a library written in Swift which makes it possible to mock data requests using a custom URLProtocol.

Features
Requirements
Usage
Communication
Installation
Release Notes
License

Features

Run all your data request unit tests offline 🎉

[x] Create mocked data requests based on an URL
[x] Create mocked data requests based on a file extension
[x] Works with URLSession using a custom protocol class
[x] Supports popular frameworks like Alamofire

Usage

Unit tests are written for the Mocker which can help you to see how it works.

Activating the Mocker

The mocker will automatically be activated for the default URL loading system like URLSession.shared after you’ve registered your first Mock.

Custom URLSessions

To make it work with your custom URLSession, the MockingURLProtocol needs to be registered:

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

Alamofire

Quite similar like registering on a custom URLSession.

let configuration = URLSessionConfiguration.af.default
configuration.protocolClasses = [MockingURLProtocol.self]
let sessionManager = Alamofire.Session(configuration: configuration)

Register Mocks

Create your mocked data

It’s recommended to create a class with all your mocked data accessible. An example of this can be found in the unit tests of this project:

public final class MockedData {
    public static let botAvatarImageResponseHead: Data = try! Data(contentsOf: Bundle(for: MockedData.self).url(forResource: "Resources/Responses/bot-avatar-image-head", withExtension: "data")!)
    public static let botAvatarImageFileUrl: URL = Bundle(for: MockedData.self).url(forResource: "wetransfer_bot_avater", withExtension: "png")!
    public static let exampleJSON: URL = Bundle(for: MockedData.self).url(forResource: "Resources/JSON Files/example", withExtension: "json")!
}

JSON Requests

let originalURL = URL(string: "https://www.wetransfer.com/example.json")!
    
let mock = Mock(url: originalURL, contentType: .json, statusCode: 200, data: [
    .get : try! Data(contentsOf: MockedData.exampleJSON) // Data containing the JSON response
])
mock.register()

URLSession.shared.dataTask(with: originalURL) { (data, response, error) in
    guard let data = data, let jsonDictionary = (try? JSONSerialization.jsonObject(with: data, options: [])) as? [String: Any] else {
        return
    }
    
    // jsonDictionary contains your JSON sample file data
    // ..
    
}.resume()

Empty Responses

let originalURL = URL(string: "https://www.wetransfer.com/api/foobar")!
var request = URLRequest(url: originalURL)
request.httpMethod = "PUT"
    
let mock = Mock(request: request, statusCode: 204)
mock.register()

URLSession.shared.dataTask(with: originalURL) { (data, response, error) in
    // ....
}.resume()

Ignoring the query

Some URLs like authentication URLs contain timestamps or UUIDs in the query. To mock these you can ignore the Query for a certain URL:

/// Would transform to "https://www.example.com/api/authentication" for example.
let originalURL = URL(string: "https://www.example.com/api/authentication?oauth_timestamp=151817037")!
    
let mock = Mock(url: originalURL, ignoreQuery: true, contentType: .json, statusCode: 200, data: [
    .get : try! Data(contentsOf: MockedData.exampleJSON) // Data containing the JSON response
])
mock.register()

URLSession.shared.dataTask(with: originalURL) { (data, response, error) in
    guard let data = data, let jsonDictionary = (try? JSONSerialization.jsonObject(with: data, options: [])) as? [String: Any] else {
        return
    }
    
    // jsonDictionary contains your JSON sample file data
    // ..
    
}.resume()

File extensions

let imageURL = URL(string: "https://www.wetransfer.com/sample-image.png")!

Mock(fileExtensions: "png", contentType: .imagePNG, statusCode: 200, data: [
    .get: try! Data(contentsOf: MockedData.botAvatarImageFileUrl)
]).register()

URLSession.shared.dataTask(with: imageURL) { (data, response, error) in
    let botAvatarImage: UIImage = UIImage(data: data!)! // This is the image from your resources.
}.resume()

Custom HEAD and GET response

let exampleURL = URL(string: "https://www.wetransfer.com/api/endpoint")!

Mock(url: exampleURL, contentType: .json, statusCode: 200, data: [
    .head: try! Data(contentsOf: MockedData.headResponse),
    .get: try! Data(contentsOf: MockedData.exampleJSON)
]).register()

URLSession.shared.dataTask(with: exampleURL) { (data, response, error) in
	// data is your mocked data
}.resume()

Custom DataType

In addition to the already build in static DataType implementations it is possible to create custom ones that will be used as the value to the Content-Type header key.

let xmlURL = URL(string: "https://www.wetransfer.com/sample-xml.xml")!

Mock(fileExtensions: "png", contentType: .init(name: "xml", headerValue: "text/xml"), statusCode: 200, data: [
    .get: try! Data(contentsOf: MockedData.sampleXML)
]).register()

URLSession.shared.dataTask(with: xmlURL) { (data, response, error) in
    let sampleXML: Data = data // This is the xml from your resources.
}.resume(

Delayed responses

Sometimes you want to test if the cancellation of requests is working. In that case, the mocked request should not finish immediately and you need a delay. This can be added easily:

let exampleURL = URL(string: "https://www.wetransfer.com/api/endpoint")!

var mock = Mock(url: exampleURL, contentType: .json, statusCode: 200, data: [
    .head: try! Data(contentsOf: MockedData.headResponse),
    .get: try! Data(contentsOf: MockedData.exampleJSON)
])
mock.delay = DispatchTimeInterval.seconds(5)
mock.register()

Redirect responses

Sometimes you want to mock short URLs or other redirect URLs. This is possible by saving the response and mocking the redirect location, which can be found inside the response:

Date: Tue, 10 Oct 2017 07:28:33 GMT
Location: https://wetransfer.com/redirect

By creating a mock for the short URL and the redirect URL, you can mock redirect and test this behavior:

let urlWhichRedirects: URL = URL(string: "https://we.tl/redirect")!
Mock(url: urlWhichRedirects, contentType: .html, statusCode: 200, data: [.get: try! Data(contentsOf: MockedData.redirectGET)]).register()
Mock(url: URL(string: "https://wetransfer.com/redirect")!, contentType: .json, statusCode: 200, data: [.get: try! Data(contentsOf: MockedData.exampleJSON)]).register()

Ignoring URLs

As the Mocker catches all URLs by default when registered, you might end up with a fatalError thrown in cases you don’t need a mocked request. In that case, you can ignore the URL:

let ignoredURL = URL(string: "www.wetransfer.com")!
Mocker.ignore(ignoredURL)

However, if you need the Mocker to catch only mocked URLs and ignore every other URL, you can set the mode attribute to .optin.

Mocker.mode = .optin

If you want to set the original mode back, you have just to set it to .optout.

Mocker.mode = .optout

Mock errors

You can request a Mock to return an error, allowing testing of error handling.

Mock(url: originalURL, contentType: .json, statusCode: 500, data: [.get: Data()],
     requestError: TestExampleError.example).register()

URLSession.shared.dataTask(with: originalURL) { (data, urlresponse, err) in
    XCTAssertNil(data)
    XCTAssertNil(urlresponse)
    XCTAssertNotNil(err)
    if let err = err {
        // there's not a particularly elegant way to verify an instance
        // of an error, but this is a convenient workaround for testing
        // purposes
        XCTAssertEqual("example", String(describing: err))
    }

    expectation.fulfill()
}.resume()

Mock callbacks

You can register on Mock callbacks to make testing easier.

var mock = Mock(url: request.url!, contentType: .json, statusCode: 200, data: [.post: Data()])
mock.onRequestHandler = OnRequestHandler(httpBodyType: [[String:String]].self, callback: { request, postBodyArguments in
    XCTAssertEqual(request.url, mock.request.url)
    XCTAssertEqual(expectedParameters, postBodyArguments)
    onRequestExpectation.fulfill()
})
mock.completion = {
    endpointIsCalledExpectation.fulfill()
}
mock.register()

Mock expectations

Instead of setting the completion and onRequest you can also make use of expectations:

var mock = Mock(url: url, contentType: .json, statusCode: 200, data: [.get: Data()])
let requestExpectation = expectationForRequestingMock(&mock)
let completionExpectation = expectationForCompletingMock(&mock)
mock.register()

URLSession.shared.dataTask(with: URLRequest(url: url)).resume()

wait(for: [requestExpectation, completionExpectation], timeout: 2.0)

Unregister Mocks

Clear all registered mocks

You can clear all registered mocks:

Mocker.removeAll()

Communication

If you found a bug, open an issue.
If you have a feature request, open an issue.
If you want to contribute, submit a pull request.

Installation

Carthage

Carthage is a decentralized dependency manager that builds your dependencies and provides you with binary frameworks.

You can install Carthage with Homebrew using the following command:

$ brew update
$ brew install carthage

To integrate Mocker into your Xcode project using Carthage, specify it in your Cartfile:

github "WeTransfer/Mocker" ~> 3.0.0

Run carthage update to build the framework and drag the built Mocker.framework into your Xcode project.

Swift Package Manager

The Swift Package Manager is a tool for managing the distribution of Swift code. It’s integrated with the Swift build system to automate the process of downloading, compiling, and linking dependencies.

Manifest File

Add Mocker as a package to your Package.swift file and then specify it as a dependency of the Target in which you wish to use it.

import PackageDescription

let package = Package(
    name: "MyProject",
    platforms: [
       .macOS(.v10_15)
    ],
    dependencies: [
        .package(url: "https://github.com/WeTransfer/Mocker.git", .upToNextMajor(from: "3.0.0"))
    ],
    targets: [
        .target(
            name: "MyProject",
            dependencies: ["Mocker"]),
        .testTarget(
            name: "MyProjectTests",
            dependencies: ["MyProject"]),
    ]
)

Xcode

To add Mocker as a dependency to your Xcode project, select File > Swift Packages > Add Package Dependency and enter the repository URL.

Resolving Build Errors

If you get the following error: cannot find auto-link library XCTest and XCTestSwiftSupport, set the following property under Build Options from No to Yes.
ENABLE_TESTING_SEARCH_PATHS to YES

Manually

If you prefer not to use any of the aforementioned dependency managers, you can integrate Mocker into your project manually.

Embedded Framework

Open up Terminal, cd into your top-level project directory, and run the following command “if” your project is not initialized as a git repository:
```
$ git init
```

Add Mocker as a git submodule by running the following command:

$ git submodule add https://github.com/WeTransfer/Mocker.git

Open the new Mocker folder, and drag the Mocker.xcodeproj into the Project Navigator of your application’s Xcode project.

It should appear nested underneath your application’s blue project icon. Whether it is above or below all the other Xcode groups does not matter.
Select the Mocker.xcodeproj in the Project Navigator and verify the deployment target matches that of your application target.
Next, select your application project in the Project Navigator (blue project icon) to navigate to the target configuration window and select the application target under the “Targets” heading in the sidebar.
In the tab bar at the top of that window, open the “General” panel.
Click on the + button under the “Embedded Binaries” section.
Select Mocker.framework.
And that’s it!

The Mocker.framework is automagically added as a target dependency, linked framework and embedded framework in a copy files build phase which is all you need to build on the simulator and a device.

Release Notes

See CHANGELOG.md for a list of changes.

License

Mocker is available under the MIT license. See the LICENSE file for more info.