Espresso
- 2 minsandroidx.test.espresso:espresso-core
This core Espresso dependency is included by default when you make a new Android project. It contains the basic testing code for most views and actions on them.
Turn off animations
Espresso tests run on a real device and thus are instrumentation tests by nature. One issue that arises is animations: If an animation lags and you try to test if a view is on screen, but it’s still animating, Espresso can accidentally fail a test. This can make Espresso tests flaky.
For Espresso UI testing, it’s best practice to turn animations off (also your test will run faster!):
- On your testing device, go to Settings > Developer options.
- Disable these three settings: Window animation scale, Transition animation scale, and Animator duration scale.
Look at an Espresso test
Before you write an Espresso test, take a look at some Espresso code.
onView(withId(R.id.task_detail_complete_checkbox)).perform(click()).check(matches(isChecked()))
What this statement does is find the checkbox view with the id task_detail_complete_checkbox, clicks it, then asserts that it is checked.
The majority of Espresso statements are made up of four parts:
onView
onView is an example of a static Espresso method that starts an Espresso statement. onView is one of the most common ones, but there are other options, such as onData.
withId(R.id.task_detail_title_text)
withId is an example of a ViewMatcher which gets a view by its ID. There are other view matchers which you can look up in the documentation.
perform(click())
The perform method which takes a ViewAction. A ViewAction is something that can be done to the view, for example here, it’s clicking the view.
check(matches(isChecked()))
check which takes a ViewAssertion. ViewAssertions check or asserts something about the view. The most common ViewAssertion you’ll use is the matches assertion. To finish the assertion, use another ViewMatcher, in this case isChecked.
