UI Testing & Integration Testing

📖 Concept

UI testing validates the app's behavior from the user's perspective. At the senior level, you should design a testing strategy that balances speed and coverage.

The testing pyramid:

      /  E2E Tests  \      Few, slow, high confidence
     / UI Tests      \     Moderate count
    / Integration     \    Moderate count
   /  Unit Tests       \   Many, fast, low cost

UI testing frameworks:

Compose Testing: Built-in test rules for Compose UIs. Find by semantics, perform actions, assert state.
Espresso: For View-based UIs. Find by ID/text, perform actions, check assertions.
UI Automator: Tests across apps (system UI, notifications, permissions).
Robolectric: Run Android tests on JVM without emulator. Very fast.

Screenshot testing: Compare rendered UI against reference screenshots. Catches visual regressions. Libraries: Paparazzi, Roborazzi, Compose Preview Screenshot Testing.

Integration testing: Tests multiple components working together (ViewModel + Repository + FakeDataSource). Runs on device/emulator. Uses Hilt's @TestInstallIn to replace production modules.

💻 Code Example

codeTap to expand ⛶

1// Compose UI test
2class TaskListScreenTest {
3    @get:Rule
4    val composeRule = createComposeRule()
5    
6    @Test
7    fun displaysTasks_whenLoaded() {
8        val tasks = listOf(
9            Task("1", "Buy groceries", false),
10            Task("2", "Write tests", true)
11        )
12        
13        composeRule.setContent {
14            TaskListScreen(
15                state = TaskUiState.Success(tasks),
16                onToggle = {},
17                onDelete = {}
18            )
19        }
20        
21        // Assert tasks are displayed
22        composeRule.onNodeWithText("Buy groceries").assertIsDisplayed()
23        composeRule.onNodeWithText("Write tests").assertIsDisplayed()
24        
25        // Assert completed task has different visual
26        composeRule.onNodeWithText("Write tests")
27            .assertHasClickAction()
28    }
29    
30    @Test
31    fun showsLoadingIndicator_whenLoading() {
32        composeRule.setContent {
33            TaskListScreen(
34                state = TaskUiState.Loading,
35                onToggle = {},
36                onDelete = {}
37            )
38        }
39        
40        composeRule.onNodeWithContentDescription("Loading")
41            .assertIsDisplayed()
42    }
43    
44    @Test
45    fun callsOnToggle_whenTaskClicked() {
46        var toggledId: String? = null
47        
48        composeRule.setContent {
49            TaskListScreen(
50                state = TaskUiState.Success(listOf(Task("1", "Test", false))),
51                onToggle = { toggledId = it },
52                onDelete = {}
53            )
54        }
55        
56        composeRule.onNodeWithText("Test").performClick()
57        assertEquals("1", toggledId)
58    }
59}
60
61// Integration test with Hilt
62@HiltAndroidTest
63@RunWith(AndroidJUnit4::class)
64class TaskFeatureTest {
65    @get:Rule(order = 0)
66    val hiltRule = HiltAndroidRule(this)
67    
68    @get:Rule(order = 1)
69    val composeRule = createAndroidComposeRule<MainActivity>()
70    
71    @BindValue // Replace real repository with fake
72    val repository: TaskRepository = FakeTaskRepository()
73    
74    @Before
75    fun setup() {
76        hiltRule.inject()
77    }
78    
79    @Test
80    fun createAndCompleteTask_endToEnd() {
81        // Add a task
82        composeRule.onNodeWithContentDescription("Add Task").performClick()
83        composeRule.onNodeWithTag("task_input").performTextInput("New task")
84        composeRule.onNodeWithText("Save").performClick()
85        
86        // Verify it appears
87        composeRule.onNodeWithText("New task").assertIsDisplayed()
88        
89        // Toggle complete
90        composeRule.onNodeWithText("New task").performClick()
91        
92        // Verify completion state
93        composeRule.onNodeWithText("New task")
94            .assertExists() // Still visible but marked complete
95    }
96}

🏋️ Practice Exercise

Practice:

Write Compose UI tests for a login screen (email validation, button state, error display)
Create a screenshot test using Paparazzi for a card component
Write an integration test that uses Hilt's @BindValue to inject fakes
Test navigation between two screens using the Navigation test artifact
Set up Robolectric for fast JVM-based UI tests

⚠️ Common Mistakes

Testing UI implementation details (view IDs) instead of user-visible behavior (text, content descriptions)
Not adding testTags/semantics to Compose components — makes testing impossible without them
Running all tests as instrumented tests — use Robolectric for fast feedback loop
Not testing error states — only testing the happy path misses the most common UX issues

💼 Interview Questions

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