settings: exercise the keep-screen-on toggle in tests

The toggle's behaviour was untested: deleting the Modifier.keepScreenOn(),
hard-coding the row's request or emptying the Switch handler all left the
suite green, so none of the three new code paths were actually pinned.

- NowPlayingKeepScreenOnTest renders Now Playing and asserts a view in the
  activity tree holds the screen on while the flag is set and releases it
  once the flag clears.
- SettingsScreenTest now covers off->on and on->off on the row, and the
  Switch itself, instead of only the off->on row click.
- Remember the keep-screen-on flow so NowPlayingRoute stops tearing down
  and rebuilding its DataStore collector on every position tick.

app/src/main/kotlin/com/subtracks/ui/playback/NowPlayingScreen.kt

@@ -196,7 +196,7 @@ fun NowPlayingRoute(
     userPreferences: UserPreferences = koinInject(),
 ) {
     val state by controller.state.collectAsStateWithLifecycle()
-    val keepScreenOn by userPreferences.keepScreenOn().collectAsStateWithLifecycle(initialValue = false)
+    val keepScreenOn by remember { userPreferences.keepScreenOn() }.collectAsStateWithLifecycle(initialValue = false)
     val positionMs by controller.positionMs.collectAsStateWithLifecycle()
     val sourceId = state.context?.sourceId
     val songId = state.item?.id

app/src/test/kotlin/com/subtracks/ui/playback/NowPlayingKeepScreenOnTest.kt

@@ -0,0 +1,85 @@
+package com.subtracks.ui.playback
+
+import android.view.View
+import android.view.ViewGroup
+import androidx.activity.ComponentActivity
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.test.junit4.v2.createAndroidComposeRule
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import com.subtracks.data.model.CoverArtRef
+import com.subtracks.playback.PlaybackState
+import com.subtracks.playback.QueueItem
+import com.subtracks.ui.theme.SubtracksTheme
+import com.subtracks.ui.theme.artworkColorsFromSeed
+import org.junit.Assert.assertNotNull
+import org.junit.Assert.assertNull
+import org.junit.Rule
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.robolectric.annotation.GraphicsMode
+
+@RunWith(AndroidJUnit4::class)
+@GraphicsMode(GraphicsMode.Mode.NATIVE)
+class NowPlayingKeepScreenOnTest {
+    @get:Rule
+    val composeRule = createAndroidComposeRule<ComponentActivity>()
+
+    private val state =
+        PlaybackState(
+            item =
+                QueueItem(
+                    id = "s-eiirp",
+                    title = "Everything In Its Right Place",
+                    artist = "Radiohead",
+                    album = "Kid A",
+                    coverArtId = "art-al-kid-a",
+                ),
+            isPlaying = true,
+            durationMs = 251_000,
+            hasNext = true,
+            hasPrevious = false,
+        )
+
+    @Test
+    fun theScreenOnFlagTracksTheSetting() {
+        var keepScreenOn by mutableStateOf(true)
+        composeRule.setContent {
+            SubtracksTheme {
+                NowPlayingScreen(
+                    state = state,
+                    positionMs = 62_000,
+                    title = "Kid A",
+                    coverArt = CoverArtRef("art-al-kid-a", "test:art-al-kid-a"),
+                    artwork = artworkColorsFromSeed(android.graphics.Color.rgb(120, 80, 200)),
+                    onBack = {},
+                    onQueue = {},
+                    onPlayPause = {},
+                    onNext = {},
+                    onPrevious = {},
+                    onSeek = {},
+                    keepScreenOn = keepScreenOn,
+                )
+            }
+        }
+        composeRule.waitForIdle()
+        assertNotNull("now playing should hold the screen on", viewHoldingTheScreenOn())
+
+        composeRule.runOnIdle { keepScreenOn = false }
+        composeRule.waitForIdle()
+        assertNull("clearing the setting should release the screen-on flag", viewHoldingTheScreenOn())
+    }
+
+    private fun viewHoldingTheScreenOn(): View? = findKeepingScreenOn(composeRule.activity.window.decorView)
+
+    private fun findKeepingScreenOn(view: View): View? {
+        if (view.keepScreenOn) return view
+        if (view is ViewGroup) {
+            for (index in 0 until view.childCount) {
+                findKeepingScreenOn(view.getChildAt(index))?.let { return it }
+            }
+        }
+        return null
+    }
+}

app/src/test/kotlin/com/subtracks/ui/settings/SettingsScreenTest.kt

@@ -1,8 +1,10 @@
 package com.subtracks.ui.settings
 
 import androidx.activity.ComponentActivity
+import androidx.compose.ui.test.hasAnySibling
 import androidx.compose.ui.test.hasScrollToNodeAction
 import androidx.compose.ui.test.hasText
+import androidx.compose.ui.test.isToggleable
 import androidx.compose.ui.test.junit4.v2.createAndroidComposeRule
 import androidx.compose.ui.test.onAllNodesWithText
 import androidx.compose.ui.test.onNodeWithText
@@ -27,8 +29,44 @@ class SettingsScreenTest {
     val composeRule = createAndroidComposeRule<ComponentActivity>()
 
     @Test
-    fun theKeepScreenOnRowToggles() {
+    fun theKeepScreenOnRowTurnsTheSettingOn() {
         var requested: Boolean? = null
+        renderSettings(keepScreenOn = false) { requested = it }
+
+        composeRule.onNodeWithText("Keep screen on").performClick()
+        composeRule.waitForIdle()
+
+        assertEquals(true, requested)
+    }
+
+    @Test
+    fun theKeepScreenOnRowTurnsTheSettingOff() {
+        var requested: Boolean? = null
+        renderSettings(keepScreenOn = true) { requested = it }
+
+        composeRule.onNodeWithText("Keep screen on").performClick()
+        composeRule.waitForIdle()
+
+        assertEquals(false, requested)
+    }
+
+    @Test
+    fun theKeepScreenOnSwitchTurnsTheSettingOn() {
+        var requested: Boolean? = null
+        renderSettings(keepScreenOn = false) { requested = it }
+
+        composeRule
+            .onNode(isToggleable() and hasAnySibling(hasText("Keep screen on")), useUnmergedTree = true)
+            .performClick()
+        composeRule.waitForIdle()
+
+        assertEquals(true, requested)
+    }
+
+    private fun renderSettings(
+        keepScreenOn: Boolean,
+        onKeepScreenOnChange: (Boolean) -> Unit,
+    ) {
         composeRule.setContent {
             SubtracksTheme {
                 SettingsScreen(
@@ -40,7 +78,7 @@ class SettingsScreenTest {
                     downloadQuality = StreamQuality(),
                     downloadOverMetered = false,
                     scrobbling = false,
-                    keepScreenOn = false,
+                    keepScreenOn = keepScreenOn,
                     onSelectSource = {},
                     onEditServer = {},
                     onWifiQualityChange = {},
@@ -49,7 +87,7 @@ class SettingsScreenTest {
                     onDownloadQualityChange = {},
                     onDownloadOverMeteredChange = {},
                     onScrobblingChange = {},
-                    onKeepScreenOnChange = { requested = it },
+                    onKeepScreenOnChange = onKeepScreenOnChange,
                     onAddServer = {},
                     onOpenDownloads = {},
                     onOpenLicenses = {},
@@ -60,9 +98,6 @@ class SettingsScreenTest {
         }
         awaitText("Add server")
         composeRule.onNode(hasScrollToNodeAction()).performScrollToNode(hasText("Keep screen on"))
-        composeRule.onNodeWithText("Keep screen on").performClick()
-        composeRule.waitForIdle()
-        assertEquals(true, requested)
     }
 
     private fun awaitText(text: String) {