How to test if a fragment is visible with Espresso

Question

I wrote a very simple Activity with a Button. When the button is clicked, I will start a new Fragment. Now I want to test this logic in my Espresso UI Test. So I wrote this UI Test for my Activity

@RunWith(AndroidJUnit4::class)
@LargeTest
class MainMenuUiTest {

@get: Rule
val activityTestRule: ActivityTestRule<MainActivity> = ActivityTestRule(MainActivity::class.java)

 @Test
 fun switchToFragment() {
     onView(withId(R.id.btn)).perform()
 }

}

How can I test that my Fragment is displayed when the button is clicked?

Answer 1

Try the following:

@Test
fun switchToFragment() {
    onView(withId(R.id.btn)).perform(click())
    onView(withId(R.id.fragment)).check(matches(isDisplayed()))
}

If you're just learning about Espresso, the official guide is a good place to start. Also, here's the Espresso cheat sheet.