Compose ui testing

Compose UI Testing & Screenshot Tests

Instructions

1. Dependencies

androidTestImplementation(platform(libs.androidx.compose.bom))
androidTestImplementation("androidx.compose.ui:ui-test-junit4")
androidTestImplementation("androidx.test.ext:junit:1.2.1")
androidTestImplementation("androidx.test.espresso:espresso-core:3.6.1")
debugImplementation("androidx.compose.ui:ui-test-manifest")

// Pick ONE screenshot framework per module:
// JVM-only (no emulator, very fast):
testImplementation("app.cash.paparazzi:paparazzi:1.3.5")
// Or Robolectric-based (runs Compose effects, closer to runtime):
testImplementation("io.github.takahirom.roborazzi:roborazzi:1.32.2")
testImplementation("io.github.takahirom.roborazzi:roborazzi-compose:1.32.2")
testImplementation("org.robolectric:robolectric:4.14")

2. Compose Rule Types

Rule	Purpose
createComposeRule()	Pure composable under a host Activity. Fastest instrumented option.
createAndroidComposeRule<MyActivity>()	Launches a real Activity — needed for navigation, Hilt injection, AndroidView.
createEmptyComposeRule()	You launch your own scenario; use when sharing state across activities.

@get:Rule val rule = createAndroidComposeRule<MainActivity>()

@Test fun showsArticleTitle() {
    rule.setContent { AppTheme { ArticleCard(fakeArticle) } }
    rule.onNodeWithText("Hello").assertIsDisplayed()
    rule.onNodeWithContentDescription("Bookmark").performClick()
}

3. Semantics Matchers

Favor matchers that survive UI refactors:

onNodeWithText("Save")
onNodeWithContentDescription("Back")
onNodeWithTag("articleList")                          // test tag, last resort
onNode(hasText("Save") and isEnabled())
onAllNodes(hasTestTag("articleRow")).assertCountEquals(3)

Set a tag when nothing semantic uniquely identifies the node:

LazyColumn(Modifier.testTag("articleList")) { /* ... */ }

Keep testTag rare; prefer labels, headings, roles from real accessibility content.

4. Synchronization

Compose test rules auto-sync to idle. Only override when you introduce external async:

rule.mainClock.autoAdvance = false
rule.onNodeWithText("Start").performClick()
rule.mainClock.advanceTimeBy(500)   // control animations precisely

For background work, pair with IdlingResources or inject a TestDispatcher so the test controls time via runTest.

5. Gesture and Input

rule.onNodeWithTag("articleList").performScrollToIndex(20)
rule.onNodeWithText("Search").performTextInput("kotlin")
rule.onNode(isFocusable()).performImeAction()
rule.onNodeWithTag("slider").performTouchInput { swipeRight() }

6. Navigation Tests

@get:Rule val rule = createAndroidComposeRule<MainActivity>()

@Test fun opensDetailOnTap() {
    rule.onNodeWithText("Kotlin on Android").performClick()
    rule.onNodeWithTag("articleDetail").assertIsDisplayed()
    Espresso.pressBack()
    rule.onNodeWithText("Kotlin on Android").assertIsDisplayed()
}

7. Hilt in Instrumented Tests

@HiltAndroidTest
class ArticlesFlowTest {
    @get:Rule(order = 0) val hilt = HiltAndroidRule(this)
    @get:Rule(order = 1) val compose = createAndroidComposeRule<HiltTestActivity>()

    @BindValue @JvmField val fakeRepo: ArticleRepository = FakeArticleRepository()

    @Test fun rendersFakeData() {
        hilt.inject()
        compose.setContent { AppTheme { ArticlesRoute(onOpen = {}) } }
        compose.onNodeWithText(FakeArticleRepository.FIRST_TITLE).assertIsDisplayed()
    }
}

Use @BindValue to swap production bindings for fakes per test.

8. Screenshot Tests — Paparazzi (JVM)

class ArticleCardPaparazzi {
    @get:Rule val paparazzi = Paparazzi(
        deviceConfig = DeviceConfig.PIXEL_5,
        theme = "Theme.Material3.DayNight",
        renderingMode = SessionParams.RenderingMode.SHRINK,
    )

    @Test fun light() = paparazzi.snapshot {
        AppTheme(darkTheme = false) { ArticleCard(sampleArticle) }
    }

    @Test fun dark() = paparazzi.snapshot {
        AppTheme(darkTheme = true) { ArticleCard(sampleArticle) }
    }
}

• JVM-only. No emulator. Seconds per test.
• Cannot execute LaunchedEffect / coroutines; capture pure visual composables and freeze state inputs.
• Record goldens: ./gradlew recordPaparazzi. Verify: ./gradlew verifyPaparazzi (runs in CI).

9. Screenshot Tests — Roborazzi (Robolectric)

@RunWith(RobolectricTestRunner::class)
@Config(qualifiers = "w360dp-h800dp-port-xhdpi")
class ArticleCardRoborazzi {
    @get:Rule val rule = createComposeRule()

    @Test fun card() {
        rule.setContent { AppTheme { ArticleCard(sampleArticle) } }
        rule.onRoot().captureRoboImage("article_card_light.png")
    }
}

Roborazzi runs the Compose runtime so remember, LaunchedEffect, and lifecycle-aware state all work. Slightly slower than Paparazzi.

Pick one framework per module and stay consistent so goldens don't drift between renderers.

10. CI Integration

• Golden images live under src/test/snapshots/ (Paparazzi) or src/test/resources/roborazzi/ and are checked into Git.
• A CI job runs verifyPaparazzi / verifyRoborazziDebug. Diff images upload as artifacts for reviewers.
• Record-mode runs are gated behind a manual workflow dispatch to avoid accidental golden churn.

Checklist

• Every screen has an instrumented test that reaches every navigation edge.
• Tests prefer semantic matchers; testTag is used sparingly.
• Hilt tests swap repositories via @BindValue fakes.
• Animation tests use mainClock.autoAdvance = false to control time.
• One screenshot framework is chosen per module (Paparazzi or Roborazzi).
• Golden images are committed and verified in CI on every PR.
• Flaky tests are fixed at the source (missing idling), not Thread.sleep.