android-device-testing

Android Device Testing

Overview

Test your app on real or emulated Android devices. This skill covers instrumented testing frameworks (Espresso, UI Automator, Compose testing), device management (ADB, emulators), UI inspection (Layout Inspector), and debugging tools for on-device behavior.

When to Use

• Writing instrumented tests (UI tests that run on a device/emulator)
• Debugging behavior that only reproduces on-device
• Setting up emulators for CI or local testing
• Inspecting UI hierarchy, accessibility, or layout issues
• Verifying behavior across API levels or screen sizes

Skip when: Writing unit tests that don't need a device (use JUnit5 + MockK instead).

Core Process

Step 1: Compose UI Testing

1. Set up Compose test dependencies:

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

1. Write Compose UI tests:

@get:Rule
val composeTestRule = createComposeRule()

@Test
fun taskItem_displaysTitle() {
    composeTestRule.setContent {
        AppTheme {
            TaskItem(
                task = Task("1", "Buy groceries", false),
                onToggle = {},
                onDelete = {},
            )
        }
    }

    composeTestRule
        .onNodeWithText("Buy groceries")
        .assertIsDisplayed()
}

@Test
fun taskItem_toggleCallsCallback() {
    var toggledId: String? = null

    composeTestRule.setContent {
        AppTheme {
            TaskItem(
                task = Task("1", "Buy groceries", false),
                onToggle = { toggledId = it },
                onDelete = {},
            )
        }
    }

    composeTestRule
        .onNodeWithContentDescription("Buy groceries")
        .performClick()

    assertEquals("1", toggledId)
}

@Test
fun taskList_showsEmptyState_whenNoTasks() {
    composeTestRule.setContent {
        AppTheme {
            TaskListContent(
                uiState = TaskListUiState.Success(tasks = emptyList()),
                onToggle = {},
                onDelete = {},
            )
        }
    }

    composeTestRule
        .onNodeWithText("No tasks yet")
        .assertIsDisplayed()
}