https://stackoverflow.com/q/58573495/1271826

AsyncTest.swift

class MyAppTests: XCTestCase {
    func testIets() {
        let expectation = self.expectation(description: "doSomething")

        AsyncClass().doSomething {
            expectation.fulfill()
        }

        wait(for: [expectation], timeout: 5)
    }
}

class AsyncClass {
    func doSomething(completion: @escaping () -> Void) {
        let group = DispatchGroup()

        for _ in 0...5 {
            group.enter()

            DispatchQueue.global().async {
                Thread.sleep(forTimeInterval: 1)

                group.leave()
            }
        }

        group.notify(queue: .main) {
            completion()
        }
    }
}

@Jasperav - IMHO, it’s not advisable to introduce anti-patterns into one's codebase solely for the sake of testing, when the testing framework already provides a nice, concise mechanism to test these scenarios.

My suggestion is that you do not add blocking/synchronous methods to your code base, and instead use expectations when testing.