test1.swift

func testThatPresenterCallsShowUserNameOnVisualizerOnStart() {
    class MockVisualizer : Visualizer {
        var userName: String? = nil

        func show(userName: String) {
            self.userName = userName
        }
    }

    let presenter = Presenter(router: Router(navigationController: UINavigationController()))

    let mockVisualizer = MockVisualizer()
    presenter.visualizer = mockVisualizer
    presenter.start()

    XCTAssertEqual(mockVisualizer.userName, "Siarhei Fedartsou")
}