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Jetpack Compose by Tutorials

Second Edition · Android 13 · Kotlin 1.7 · Android Studio Dolphin

Before You Begin

Section 0: 6 chapters
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Section I: Getting Started With Jetpack Compose

Section 1: 4 chapters
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Section II: Composing User Interfaces

Section 2: 4 chapters
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Section III: Building Complex Apps With Jetpack Compose

Section 3: 5 chapters
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Section IV: UI Testing & Accessibility

Section 4: 2 chapters
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Section V: Glances & Keeping Upto Date With Jetpack Compose

Section 5: 3 chapters
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Section VI: Appendices

Section 6: 1 chapter
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14. UI Tests in Jetpack Compose
Written by Prateek Prasad

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Congratulations on wrapping up the JetReddit app. Throughout the last thirteen chapters, you learned about the fundamentals of Jetpack Compose and built the JetReddit app from the ground up.

It’s time to verify the app’s functionality and learn how UI testing works in Jetpack Compose. In this chapter, you’ll learn how to write UI tests for your screens and components in Jetpack Compose and how assertions work. Let’s jump straight in!

Loading the Starter Project

To follow along with the code examples, open this chapter’s starter project in Android Studio and select Open an existing project.

Next, navigate to 14-ui-tests-in-compose/projects and select the starter folder as the project root. Once the project opens, let it build and sync, and you’re ready to go!

It’s the same app you’ve worked on, with a few structural changes to the code.

Open the JetRedditApp.kt file. Here, the ViewModel is no longer passed as a parameter to JetRedditApp composable. Instead, you now have separate state objects and event handlers to render the UI and pass events to the parent activity hosting the composable:

@Composable
fun JetRedditApp(
    allPosts: List<PostModel>,
    myPosts: List<PostModel>,
    communities: List<String>,
    selectedCommunity: String,
    savePost: (post: PostModel) -> Unit,
    searchCommunities: (searchedText: String) -> Unit,
    communitySelected: (community: String) -> Unit,
) {
    JetRedditTheme {
        AppContent(
            allPosts,
            myPosts,
            communities,
            selectedCommunity,
            savePost,
            searchCommunities,
            communitySelected
        )
    }
}

This slight change in structure will go a long way in helping you set up the test environment in the absence of a proper dependency injection setup.

The dependencies required for testing your composables have been added to the app’s build.gradle file as shown below:

  // Compose testing dependencies
  androidTestImplementation "androidx.compose.ui:ui-test:$compose_version"
  androidTestImplementation "androidx.compose.
  ui:ui-test-junit4:$compose_version"
  debugImplementation "androidx.compose.ui:ui-test-manifest:$compose_version"

Before writing your first UI test, it’s good to understand how tests work in Jetpack Compose.

Note: Please ensure you use an emulator or device running a modern version of Android before running the tests in this chapter. Some older versions of Android may report failing tests.

Behind the Scenes of UI Tests in Jetpack Compose

UI tests for composables fall into the instrumentation test category, just like espresso tests, as you need a physical device or an emulator to run them.

Testing UI Components in Jetpack Compose

Just like previewing and deploying individual components in Jetpack Compose, you can also write UI tests for them in isolation. Testing components in isolation allows you the ease and flexibility to set up a contained environment to test individual UI variations quickly.

Writing Tests for Screens

Having covered component-level tests, it’s now time to look at how UI testing works for screens.

Writing Tests for Hybrid Screens

In a hybrid setup you will often find composables inside an XML view hierarchy and views inside composable trees.

Key Points

13. Adding View Compatibility
15. Accessibility in Jetpack Compose
Have a technical question? Want to report a bug? You can ask questions and report bugs to the book authors in our official book forum here.
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