@Test
fun shouldEnableButtonWhenValidMessageIsTyped() {
    onView(withId(R.id.messageField)).perform(typeText("you do not talk about Fight Club"))
    onView(withId(R.id.sendButton)).check(matches(isEnabled()))
}

@Test
fun shouldNotEnableButtonWhenInvalidMessageIsTyped() {
    onView(withId(R.id.messageField)).perform(typeText("Hey, let me tell you about the Fight Club"))
    onView(withId(R.id.sendButton)).check(matches(not(isEnabled())))
}