如何手动调用在RxSwift注册的手势识别器?

let recognizer = UITapGestureRecognizer()
mainView.messagesView.addGestureRecognizer(recognizer)
_ = recognizer.rx.event.bind { _ in
    self.mainView.dismissKeyboard()
}.disposed(by: bag)

但现在我需要测试一下:

func testIfKeyboardIsDismissedAfterMessageViewWasTapped() {
    let view = ThreadView()
    let model = StubThreadViewModel()
    let controller = ThreadViewController(view: view, viewModel: model)
    controller.viewDidLoad()
    let window = UIWindow()
    window.addSubview(view)
    view.textView.becomeFirstResponder()
    XCTAssertTrue(view.textView.isFirstResponder) //TRUE, test passes
    view.messageView. //Here I dont know how to force tap manually
    XCTAssertFalse(view.textView.isFirstResponder) //FALSE, test fails
}