How write unit test for receiving nsnotification asynchronous?

Question

I call rest web servic with completion handler and if succeed I send NSNotification.

The problem is how to write unit test to assert that the notification is sent in case of success.

Any help will be appreciated.

Jasonjasper

xctestexpectation, for example, could solve your problem as async invocations – Phraseogram

Answer 1

You can add an expectation for the notification:

expectationForNotification("BlaBlaNotification", object: nil) { (notification) -> Bool in

// call the method that fetches the data
sut.fetchData()  

waitForExpectationsWithTimeout(5, handler: nil)

But personally I would split this is two tests. One for the fetching of the data (tested using a stub) and one for the sending of the notification.

Chauvin

sut is short for system under test. – Chauvin

Answer 2

This is how I test notifications:

func testDataFetched() {

    weak var expectation = self.expectation(description: "testDataFetched")

    //set the notification name to whatever you called it
    NotificationCenter.default.addObserver(forName: NSNotification.Name("dataWasFetched"), object: nil, queue: nil) { notification in

        //if we got here, it means we got our notification within the timeout limit

        //optional: verify userInfo in the notification if it has any

        //call fulfill and your test will succeed; otherwise it will fail
        expectation?.fulfill()
    }

    //call your data fetch here
    sut.fetchData()

    //you must call waitForExpectations or your test will 'succeed'
    // before the notification can be received!
    // also, set the timeout long enough for your data fetch to complete
    waitForExpectations(timeout: 1.0, handler: nil)
}

Bowsprit