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Merge pull request #11 from Lickability/mock-url-session
Mock URLSession Behavior for Testing
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,41 @@ | ||
| // | ||
| // NetworkSession.swift | ||
| // Networking | ||
| // | ||
| // Created by Michael Liberatore on 5/9/23. | ||
| // Copyright © 2023 Lickability. All rights reserved. | ||
| // | ||
|
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| import Foundation | ||
| import Combine | ||
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| /// Describes an object that coordinates a group of related, network data transfer tasks. This protocol has a similar API to `URLSession` for the purpose of mocking. | ||
| public protocol NetworkSession { | ||
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| /// Creates a task that retrieves the contents of a URL based on the specified URL request object, and calls a handler upon completion. | ||
| /// - Parameters: | ||
| /// - request: A URL request object that provides the URL, cache policy, request type, body data or body stream, and so on. | ||
| /// - completionHandler: The completion handler to call when the load request is complete. This handler is executed on the delegate queue. | ||
| /// - Returns: The new session data task. | ||
| /// | ||
| /// - Note: This documentation is pulled directly from `URLSession`. | ||
| func makeDataTask(with request: URLRequest, completionHandler: @escaping @Sendable (Data?, URLResponse?, Error?) -> Void) -> NetworkSessionDataTask | ||
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| /// Returns a publisher that wraps a URL session data task for a given URL request. | ||
| /// | ||
| /// The publisher publishes data when the task completes, or terminates if the task fails with an error. | ||
| /// - Parameter request: The URL request for which to create a data task. | ||
| /// - Returns: A publisher that wraps a data task for the URL request. | ||
| /// | ||
| /// - Note: This documentation is pulled directly from `URLSession`. | ||
| func dataTaskPublisher(for request: URLRequest) -> URLSession.DataTaskPublisher | ||
| } | ||
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| extension URLSession: NetworkSession { | ||
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| // MARK: - NetworkSession | ||
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| public func makeDataTask(with request: URLRequest, completionHandler: @escaping @Sendable (Data?, URLResponse?, Error?) -> Void) -> NetworkSessionDataTask { | ||
| return dataTask(with: request, completionHandler: completionHandler) | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,20 @@ | ||
| // | ||
| // NetworkSessionDataTask.swift | ||
| // NetworkingTests | ||
| // | ||
| // Created by Michael Liberatore on 5/9/23. | ||
| // Copyright © 2023 Lickability. All rights reserved. | ||
| // | ||
|
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| import Foundation | ||
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| /// Describes a network session task that can be performed. This protocol has a similar API to `URLSessionDataTask` for the purpose of mocking. | ||
| public protocol NetworkSessionDataTask { | ||
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| /// Resumes the task, if it is suspended. | ||
| /// | ||
| /// - Note: This documentation is pulled directly from `URLSessionTask`. | ||
| func resume() | ||
| } | ||
|
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| extension URLSessionDataTask: NetworkSessionDataTask { } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,54 @@ | ||
| // | ||
| // MockNetworkSession.swift | ||
| // NetworkingTests | ||
| // | ||
| // Created by Michael Liberatore on 5/9/23. | ||
| // Copyright © 2023 Lickability. All rights reserved. | ||
| // | ||
|
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| import Foundation | ||
| import Networking | ||
|
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| /// A mocked version of `NetworkSession` to be used in tests. Allows specification of success or failure cases. | ||
| class MockNetworkSession: NetworkSession { | ||
| private let result: Result<Data, Error> | ||
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| /// Creates a new `MockNetworkSession`. | ||
| /// - Parameter result: The expected result of network requests performed by this mock. | ||
| init(result: Result<Data, Error>) { | ||
| self.result = result | ||
| } | ||
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| // MARK: - NetworkSession | ||
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| func makeDataTask(with request: URLRequest, completionHandler: @escaping @Sendable (Data?, URLResponse?, Error?) -> Void) -> NetworkSessionDataTask { | ||
| return MockNetworkSessionDataTask { [weak self] in | ||
| switch self?.result { | ||
| case .success(let data): | ||
| let response = request.url.flatMap { HTTPURLResponse(url: $0, statusCode: 200, httpVersion: nil, headerFields: nil) } | ||
| completionHandler(data, response, nil) | ||
| case .failure(let error): | ||
| let response = request.url.flatMap { HTTPURLResponse(url: $0, statusCode: 0, httpVersion: nil, headerFields: nil) } | ||
| completionHandler(nil, response, error) | ||
| case .none: | ||
| assertionFailure("`MockNetworkSession` went out of scope. Keep a reference to it for the duration of your tests.") | ||
| } | ||
| } | ||
| } | ||
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| func dataTaskPublisher(for request: URLRequest) -> URLSession.DataTaskPublisher { | ||
| return URLSession.DataTaskPublisher(request: request, session: .shared) // not currently mocked. | ||
| } | ||
| } | ||
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| private class MockNetworkSessionDataTask: NetworkSessionDataTask { | ||
| private let resumeClosure: () -> Void | ||
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| init(closure: @escaping () -> Void) { | ||
| self.resumeClosure = closure | ||
| } | ||
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| func resume() { | ||
| resumeClosure() | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,97 @@ | ||
| // | ||
| // NetworkControllerTests.swift | ||
| // NetworkingTests | ||
| // | ||
| // Created by Michael Liberatore on 5/9/23. | ||
| // Copyright © 2023 Lickability. All rights reserved. | ||
| // | ||
|
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| import XCTest | ||
| @testable import Networking | ||
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| class NetworkControllerTests: XCTestCase { | ||
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| func testAsyncAwaitSendWithFailure() async throws { | ||
| let networkController = NetworkController(networkSession: MockNetworkSession(result: .failure(NetworkError.noResponse))) | ||
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| do { | ||
| let _: [Photo] = try await networkController.send(PhotoRequest.photosList, requestBehaviors: []) | ||
| XCTFail("Should’ve caught an error before reaching here.") | ||
| } | ||
| catch { | ||
| guard let networkError = error as? NetworkError else { | ||
| XCTFail("Encountered an unexpected error type") | ||
| return | ||
| } | ||
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| switch networkError { | ||
| case .decodingError, .noData, .noResponse, .unsuccessfulStatusCode: | ||
| XCTFail("Encountered an unexpected NetworkError type") | ||
| case .underlyingNetworkingError(let underlyingError): | ||
| guard let underlyingNetworkError = underlyingError as? NetworkError else { | ||
| XCTFail("Encountered an unexpected underlying error type") | ||
| return | ||
| } | ||
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| XCTAssertEqual(underlyingNetworkError.failureReason, NetworkError.noResponse.failureReason) | ||
| } | ||
| } | ||
| } | ||
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| func testAsyncAwaitSendWithSuccess() async throws { | ||
| let photos: [Photo] = [ | ||
| Photo(albumId: 1, id: 1, title: "1", url: "", thumbnailUrl: ""), | ||
| Photo(albumId: 1, id: 2, title: "1", url: "", thumbnailUrl: ""), | ||
| Photo(albumId: 1, id: 3, title: "1", url: "", thumbnailUrl: "") | ||
| ] | ||
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| let encoder = JSONEncoder() | ||
| do { | ||
| let data = try encoder.encode(photos) | ||
| let networkController = NetworkController(networkSession: MockNetworkSession(result: .success(data))) | ||
| let photosResponse: NetworkResponse = try await networkController.send(PhotoRequest.photosList, requestBehaviors: []) | ||
| let decodedData = photosResponse.data | ||
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| XCTAssertEqual(data, decodedData) | ||
| } | ||
| catch { | ||
| XCTFail("Unexpected error occurred: \(error).") | ||
| } | ||
| } | ||
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| func testAsyncAwaitBehaviors() async throws { | ||
| let networkController = NetworkController(networkSession: MockNetworkSession(result: .failure(NetworkError.noResponse))) | ||
|
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| var requestWillSendWasCalled = false | ||
| var requestDidFinishWasCalled = false | ||
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| let behavior = TestBehavior { | ||
| requestWillSendWasCalled = true | ||
| XCTAssertFalse(requestDidFinishWasCalled, "We should’ve reached this point before `requestDidFinishWasCalled` became true.") | ||
| } didFinishClosure: { | ||
| requestDidFinishWasCalled = true | ||
| } | ||
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| do { | ||
| let _: [Photo] = try await networkController.send(PhotoRequest.photosList, requestBehaviors: [behavior]) | ||
| XCTFail("Should’ve caught an error before reaching here.") | ||
| } | ||
| catch { | ||
| XCTAssertTrue(requestWillSendWasCalled) | ||
| XCTAssertTrue(requestDidFinishWasCalled) | ||
| } | ||
| } | ||
| } | ||
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| private struct TestBehavior: RequestBehavior { | ||
| let willSendClosure: () -> Void | ||
| let didFinishClosure: () -> Void | ||
|
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| func requestWillSend(request: inout URLRequest) { | ||
| willSendClosure() | ||
| } | ||
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| func requestDidFinish(result: Result<NetworkResponse, NetworkError>) { | ||
| didFinishClosure() | ||
| } | ||
| } |