XCTest - Assert notification (not) triggered.

NotificationTestCase.swift

import XCTest

class NotificationTestCase: XCTestCase {

    func testTriggerNotification() {
        expectation(forNotification: .fooBar,
                    object: nil,
                    handler: nil)

        let notificationCenter = NotificationCenter.default
        notificationCenter.post(name: .fooBar,
                                object: self)

        waitForExpectations(timeout: 0.1, handler: nil)
    }

    func testDidNotTriggerNotification() {
        let expectation = self.expectation(forNotification: .fooBar,
                                           object: nil,
                                           handler: nil)
        expectation.isInverted = true

        // Run code that should not trigger a notification
        if false {
            let notificationCenter = NotificationCenter.default
            notificationCenter.post(name: .fooBar,
                                    object: nil)
        }

        waitForExpectations(timeout: 0.1, handler: nil)
    }
}

extension Notification.Name {
    static let fooBar = Notification.Name(rawValue: "fooBar")
}

// Run tests in playground
NotificationTestCase.defaultTestSuite.run()