The Compose Testing Philosophy

Compose testing differs fundamentally from View testing. Instead of finding views by ID and simulating touches, you interact with the semantic tree that Compose uses for accessibility. This makes tests more resilient and closer to how users actually interact with your app.

Setting Up Compose Tests

Add the testing dependencies and create your first test:

// build.gradle.kts
dependencies {
    androidTestImplementation("androidx.compose.ui:ui-test-junit4")
    debugImplementation("androidx.compose.ui:ui-test-manifest")
}

// LoginScreenTest.kt
class LoginScreenTest {
    @get:Rule
    val composeTestRule = createComposeRule()

    @Test
    fun loginButton_isDisabled_whenEmailIsEmpty() {
        composeTestRule.setContent {
            LoginScreen()
        }
        
        composeTestRule
            .onNodeWithText("Log In")
            .assertIsNotEnabled()
    }
}

Finding and Interacting with Nodes

Compose provides powerful matchers to find nodes in the semantic tree:

// Find by text
composeTestRule.onNodeWithText("Submit")

// Find by content description (accessibility)
composeTestRule.onNodeWithContentDescription("Close button")

// Find by test tag
composeTestRule.onNodeWithTag("email_input")

// Combine matchers
composeTestRule.onNode(
    hasText("Submit") and hasClickAction() and isEnabled()
)

// Perform actions
composeTestRule.onNodeWithTag("email_input")
    .performTextInput("user@example.com")
    
composeTestRule.onNodeWithText("Submit")
    .performClick()

Testing State and Recomposition

For testing state changes and async operations, use waitUntil and other synchronization utilities:

@Test
fun loadingIndicator_disappears_afterDataLoads() {
    composeTestRule.setContent {
        MyScreenWithLoading()
    }
    
    // Initially shows loading
    composeTestRule.onNodeWithTag("loading").assertIsDisplayed()
    
    // Wait for loading to complete
    composeTestRule.waitUntil(timeoutMillis = 5000) {
        composeTestRule
            .onAllNodesWithTag("loading")
            .fetchSemanticsNodes().isEmpty()
    }
    
    // Content is now visible
    composeTestRule.onNodeWithTag("content").assertIsDisplayed()
}

Screenshot Testing with Paparazzi

Screenshot tests catch visual regressions that functional tests miss. Paparazzi runs on JVM without an emulator:

class ButtonScreenshotTest {
    @get:Rule
    val paparazzi = Paparazzi(
        theme = "android:Theme.Material3.Light"
    )

    @Test
    fun primaryButton_default() {
        paparazzi.snapshot {
            PrimaryButton(text = "Click Me", onClick = {})
        }
    }
    
    @Test
    fun primaryButton_disabled() {
        paparazzi.snapshot {
            PrimaryButton(text = "Click Me", enabled = false, onClick = {})
        }
    }
}