テストケースで UIButton をタップする

import XCTest

class UITests: XCTestCase {

  override func setUp() {
    // Put setup code here. This method is called before the invocation of each test method in the class.

    // In UI tests it is usually best to stop immediately when a failure occurs.
    continueAfterFailure = false

    // UI tests must launch the application that they test. Doing this in setup will make sure it happens for each test method.
    XCUIApplication().launch()

    // In UI tests it’s important to set the initial state - such as interface orientation - required for your tests before they run. The setUp method is a good place to do this.
  }

  override func tearDown() {
    // Put teardown code here. This method is called after the invocation of each test method in the class.
  }

  func testOne() {
    let app = XCUIApplication()

    // ボタンのテキストをキーにして、ボタンを得る
    let button = app.buttons["Message"]

    // ボタンの有無をアサートチェックする
    XCTAssertTrue(button.exists)

    // ボタンをタップ
    button.tap()
}