AnySubscriber+SubjectTests.swift

//
/*
 *		Created by 游宗諭 in 2021/5/26
 *
 *		Using Swift 5.0
 *
 *		Running on macOS 11.4
 */

import Combine
import XCTest

// MARK: - MockSubject

class MockSubject: Subject {
    var capture: [SubjectEvent] = []
    
    func send(_ value: Output) {
        capture.append(.send(value))
    }
    
    func send(completion: Subscribers.Completion<Failure>) {
        capture.append(.sendcompletion( completion))
    }
    
    func send(subscription: Subscription) {
        capture.append(.sendsubscription)
    }
    
    func receive<S>(subscriber: S) where S: Subscriber, NSError == S.Failure, Int == S.Input {
        capture.append(.receivesubscriber)
    }

    typealias Output = Int
    
    typealias Failure = NSError
}

// MARK: - AnySubscriberTests

final class AnySubscriberTests: XCTestCase {
    func test() {
        let mockSubject = MockSubject()
        let sut = AnySubscriber(mockSubject)
        XCTAssertEqual(mockSubject.capture, [])
        _ = sut.receive(1)
        sut.receive(subscription: Subscriptions.empty)
        XCTAssertEqual(mockSubject.capture, [.sendsubscription])
        _ = sut.receive(1)
        XCTAssertEqual(mockSubject.capture, [.sendsubscription, .send(1)])
        sut.receive(completion: .finished)
        XCTAssertEqual(mockSubject.capture, [.sendsubscription, .send(1), .sendcompletion(.finished)])
        sut.receive(subscription: Subscriptions.empty)
        XCTAssertEqual(mockSubject.capture, [.sendsubscription, .send(1), .sendcompletion(.finished)])
    }
}

// MARK: - SubjectEvent

enum SubjectEvent: Equatable, CustomStringConvertible {
    case send(_ value: Int)
    case sendcompletion(Subscribers.Completion<NSError>)
    case sendsubscription // (subscription: Subscription)
    case receivesubscriber
    
    var description: String {
        switch self {
        case let .send(value): return "\(value)"
        case let .sendcompletion(completion): return "\(completion)"
        case .sendsubscription: return "sendsubscription"
        case .receivesubscriber: return "receivesubscriber"
        }
    }
}

 func testMirror() {
        let subject = PassthroughSubject<Int, Never>()
        let erasingSubject = AnySubscriber<Int, Never>(subject)
        let mirror = Mirror(reflecting: erasingSubject)
        XCTAssertEqual(
            String(describing: mirror.subjectType),
            "SubjectSubscriber<PassthroughSubject<Int, Never>>"
        )
    }