6.3. Instrumented tests

Instrumented tests do depend on Android and run on the emulator or a physical device. These types of tests typically incorporate interface tests. Moreover, in addition to the correction of the tests, we may be interested in their performance.

The Espresso library is used to perform interface tests. Espresso allows us to automatically interact with interface elements.

To perform Instrumented tests using Espresso, the dependencies are:

dependencies {
  testImplementation 'junit:junit:4.13.2'

  androidTestImplementation 'androidx.test.ext:junit:1.1.3'
  androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'


  androidTestImplementation "androidx.test.espresso:espresso-intents:3.4.0"
  androidTestImplementation 'androidx.test:runner:1.2.0'
  androidTestImplementation 'androidx.test:rules:1.2.0'
  implementation "androidx.test.ext:junit-ktx:1.1.3"
}

Within the androidTest folder we create a Kotlin file with a class that will represent our test.

@RunWith(AndroidJUnit4::class)
class MainActivityTest{

   @get:Rule var activityScenarioRule = activityScenarioRule<MainActivity>()

   @Test
   fun Test1() {
       onView(withId(R.id.username))
           .perform(typeText("user@mail.com"), closeSoftKeyboard())

       onView(withId(R.id.password))
           .perform(typeText("cat"), closeSoftKeyboard())

       onView(withId(R.id.login)).perform(click())

       onView(withId(R.id.error)).check(matches(withText("ERROR")))
   }
}

The Espresso library allows us to perform actions such as:

• Write a text in an EditText:

  onView(withId(R.id.username))
           .perform(typeText("user@mail.com"), closeSoftKeyboard())

• Press a button:

  onView(withId(R.id.login)).perform(click())

• Verify that a text appears in a given EditText:

  onView(withId(R.id.error)).check(matches(withText(“ERROR”)))

The following video shows a testing session. We can see how at the bottom of the screen, in the Cover browser, it reports the test result and the time that the run has lasted.

Result of a Espresso interface test.
Source: Javier Salvador (Original image) License: CC BY-NC-ND 4.0

Learn more: Following the following link to To try Espresso snippets: https://developer.android.com/guide/fragments/test