How to test if a UIControlEvents has been fired

Question

I have a library implementing a custom UIControl with a method which would fire a .valueChanged event when called. I would like to test the method

Answer 1

Apple's documentation for UIControl states that:

When a control-specific event occurs, the control calls any associated action methods right away. Action methods are dispatched through the current UIApplication object, which finds an appropriate object to handle the message, following the responder chain if needed.

When sendActions(for:) is called on a UIControl, the control will call the UIApplication's sendAction(_:to:from:for:) to deliver the event to the registered target.

Since I am testing a library without any Host Application, there is no UIApplication object. Hence, the .valueChanged event is not dispatched and the observe method does not get called.

Answer 2

You are declaring the observer object inside the test method. This means that as soon as the method completes it will be released from memory and hence is not called. Create a reference to the observer at class level in the Tests class as follows and it will work.

class Tests: XCTestCase {

    var observer: ControlEventObserver!
    func test() {
        let myExpectation = expectation(description: "event fired")
        self.observer = ControlEventObserver(expectation: myExpectation)
        let control = MyControl()
        control.addTarget(observer, action:#selector(ControlEventObserver.observe), for: .valueChanged)
        control.fire()
        waitForExpectations(timeout: 1) { error in
            XCTAssertNil(error)
        }
    }
}

You will also need the myExpectation & control to be declared in the same way else that won't be called either.