Helper methods for asynchronous tests

TestQueueing.swift

import Foundation
import Dispatch
import XCTest

extension DispatchQueue {
    
    func asyncAfter(_ seconds: TimeInterval,
                    execute work: @escaping @convention(block) () -> Void) {
        asyncAfter(deadline: DispatchTime.now() + seconds, execute: work)
    }
    
}

extension XCTestCase {
    
    func waitForExecution(on queue: DispatchQueue = .main,
                          timeout: TimeInterval = 2,
                          delay: TimeInterval = 0,
                          executing block: @escaping () -> Void) {
        let expect = expectation(description: "executing on queue")
        
        queue.asyncAfter(delay) {
            block()
            expect.fulfill()
        }
        
        wait(for: [expect], timeout: timeout + delay)
    }
    
}