feat: developer toggle for test data in debug builds

app/build.gradle.kts

@@ -83,6 +83,7 @@ android {
 
     buildFeatures {
         compose = true
+        buildConfig = true
     }
 
     testOptions {

app/src/main/java/com/podometer/MainActivity.kt

@@ -158,6 +158,7 @@ class MainActivity : ComponentActivity() {
                                 )
                                 startActivity(intent)
                             },
+                            onSetUseTestData = viewModel::setUseTestData,
                         )
                     }
 

app/src/main/java/com/podometer/data/repository/PreferencesManager.kt

@@ -60,6 +60,11 @@ class PreferencesManager @Inject constructor(
 
         /** Default onboarding complete: false (show onboarding on first launch). */
         const val DEFAULT_ONBOARDING_COMPLETE = false
+
+        val KEY_USE_TEST_DATA = booleanPreferencesKey("use_test_data")
+
+        /** Default use-test-data: false (use real sensor data). */
+        const val DEFAULT_USE_TEST_DATA = false
     }
 
     // ─── Read ────────────────────────────────────────────────────────────────
@@ -101,6 +106,15 @@ class PreferencesManager @Inject constructor(
             prefs[KEY_NOTIFICATION_STYLE] ?: DEFAULT_NOTIFICATION_STYLE
         }
 
+    /**
+     * Emits whether the debug test-data mode is enabled.
+     * Defaults to `false` (use real sensor data).
+     */
+    fun useTestData(): Flow<Boolean> =
+        dataStore.data.map { prefs ->
+            prefs[KEY_USE_TEST_DATA] ?: DEFAULT_USE_TEST_DATA
+        }
+
     /**
      * Emits whether the user has completed the onboarding flow.
      * Defaults to `false` on first launch so the onboarding screen is shown.
@@ -163,6 +177,13 @@ class PreferencesManager @Inject constructor(
         }
     }
 
+    /** Persists the given [enabled] flag for the debug test-data mode. */
+    suspend fun setUseTestData(enabled: Boolean) {
+        dataStore.edit { prefs ->
+            prefs[KEY_USE_TEST_DATA] = enabled
+        }
+    }
+
     /**
      * Persists the given [complete] flag as the onboarding completion status.
      *

app/src/main/java/com/podometer/ui/activities/ActivitiesViewModel.kt

@@ -3,6 +3,7 @@ package com.podometer.ui.activities
 
 import androidx.lifecycle.ViewModel
 import androidx.lifecycle.viewModelScope
+import com.podometer.data.repository.PreferencesManager
 import com.podometer.domain.model.ActivitySession
 import com.podometer.domain.model.TransitionEvent
 import com.podometer.domain.usecase.RecomputeActivitySessionsUseCase
@@ -13,6 +14,7 @@ import kotlinx.coroutines.flow.SharingStarted
 import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.combine
 import kotlinx.coroutines.flow.flatMapLatest
+import kotlinx.coroutines.flow.flowOf
 import kotlinx.coroutines.flow.stateIn
 import java.time.LocalDate
 import javax.inject.Inject
@@ -43,6 +45,7 @@ data class ActivitiesUiState(
 @HiltViewModel
 class ActivitiesViewModel @Inject constructor(
     private val recomputeActivitySessions: RecomputeActivitySessionsUseCase,
+    private val preferencesManager: PreferencesManager,
 ) : ViewModel() {
 
     companion object {
@@ -56,18 +59,37 @@ class ActivitiesViewModel @Inject constructor(
 
     /** Combined UI state emitted to the Activities screen. */
     @OptIn(ExperimentalCoroutinesApi::class)
-    val uiState: StateFlow<ActivitiesUiState> = _selectedDate.flatMapLatest { date ->
+    val uiState: StateFlow<ActivitiesUiState> = combine(
+        _selectedDate,
+        preferencesManager.useTestData(),
+    ) { date, useTest -> date to useTest }.flatMapLatest { (date, useTestData) ->
         val nowMillis = System.currentTimeMillis()
-        recomputeActivitySessions(date, nowMillis).combine(
-            MutableStateFlow(date),
-        ) { sessions, selectedDate ->
-            ActivitiesUiState(
-                selectedDate = selectedDate,
-                sessions = sessions,
-                isToday = selectedDate == LocalDate.now(),
-                dateLabel = formatDateLabel(selectedDate),
-                isLoading = false,
-            )
+
+        if (useTestData) {
+            combine(
+                flowOf(TestDataGenerator.generateSessions(date)),
+                flowOf(Unit),
+            ) { sessions, _ ->
+                ActivitiesUiState(
+                    selectedDate = date,
+                    sessions = sessions,
+                    isToday = date == LocalDate.now(),
+                    dateLabel = formatDateLabel(date),
+                    isLoading = false,
+                )
+            }
+        } else {
+            recomputeActivitySessions(date, nowMillis).combine(
+                MutableStateFlow(date),
+            ) { sessions, selectedDate ->
+                ActivitiesUiState(
+                    selectedDate = selectedDate,
+                    sessions = sessions,
+                    isToday = selectedDate == LocalDate.now(),
+                    dateLabel = formatDateLabel(selectedDate),
+                    isLoading = false,
+                )
+            }
         }
     }.stateIn(
         scope = viewModelScope,