CustomAsyncHandler.swift

final class ImageLoaderTests: XCTestCase {
  func testLoadingImageSuccessfully() {
    execute(withTimeout: 5) {
      let imageLoader = ImageLoader()
      _ = try await imageLoader.loadImage(for: "identifier")
    }
  }
}

extension XCTestCase {
  func execute(withTimeout timeout: TimeInterval, file: StaticString = #filePath, line: UInt = #line, workItem: @escaping () async throws -> Void) {
    let expectation = expectation(description: "wait for async function")
    var workItemError: Error?
    let captureError = { workItemError = $0 }
        
    let task = Task {
      do {
        try await workItem()
      }
      catch {
        captureError(error)
      }
      expectation.fulfill()
    }
    waitForExpectations(timeout: timeout) { _ in
      if let error = workItemError {
        XCTFail("\(error)", file: file, line: line)
      }      
      task.cancel()
    }
  }
}