For #25538 - Add a simple way to check if the default wallpaper is to be shown

A previous check for whether the persisted name of the current wallpaper is
empty made checking whether the default wallpaper is to be shown brittle.
Instead of duplicating such a check in multiple places it is now extracted in
one method that can be used in multiple places including the new telemetry.

app/src/main/java/org/mozilla/fenix/wallpapers/WallpaperManager.kt

@@ -115,10 +115,10 @@ class WallpaperManager(
         }
 
     private fun getCurrentWallpaperFromSettings(): Wallpaper {
-        val currentWallpaper = settings.currentWallpaper
-        return if (currentWallpaper.isEmpty()) {
+        return if (isDefaultTheCurrentWallpaper(settings)) {
             defaultWallpaper
         } else {
+            val currentWallpaper = settings.currentWallpaper
             wallpapers.find { it.name == currentWallpaper }
                 ?: fileManager.lookupExpiredWallpaper(currentWallpaper)
                 ?: defaultWallpaper
@@ -240,6 +240,13 @@ class WallpaperManager(
     }
 
     companion object {
+        /**
+         *  Get whether the default wallpaper should be used.
+         */
+        fun isDefaultTheCurrentWallpaper(settings: Settings): Boolean = with(settings.currentWallpaper) {
+            return isEmpty() || equals(defaultWallpaper.name)
+        }
+
         val defaultWallpaper = Wallpaper.Default
         private val localWallpapers: List<Wallpaper.Local> = listOf(
             Wallpaper.Local.Firefox("amethyst", R.drawable.amethyst),

app/src/test/java/org/mozilla/fenix/wallpapers/WallpaperManagerTest.kt

@@ -166,6 +166,33 @@ class WallpaperManagerTest {
         assertEquals(expected, wallpaperManager.currentWallpaper)
     }
 
+    @Test
+    fun `GIVEN no custom wallpaper set WHEN checking whether the current wallpaper should be default THEN return true`() {
+        every { mockSettings.currentWallpaper } returns ""
+
+        val result = WallpaperManager.isDefaultTheCurrentWallpaper(mockSettings)
+
+        assertTrue(result)
+    }
+
+    @Test
+    fun `GIVEN the default wallpaper is set to be shown WHEN checking whether the current wallpaper should be default THEN return true`() {
+        every { mockSettings.currentWallpaper } returns WallpaperManager.defaultWallpaper.name
+
+        val result = WallpaperManager.isDefaultTheCurrentWallpaper(mockSettings)
+
+        assertTrue(result)
+    }
+
+    @Test
+    fun `GIVEN a custom wallpaper is set to be shown WHEN checking whether the current wallpaper should be default THEN return false`() {
+        every { mockSettings.currentWallpaper } returns "test"
+
+        val result = WallpaperManager.isDefaultTheCurrentWallpaper(mockSettings)
+
+        assertFalse(result)
+    }
+
     private enum class TimeRelation {
         BEFORE,
         NOW,