diff --git a/app/src/test/java/org/oxycblt/auxio/music/user/DeviceLibraryTest.kt b/app/src/test/java/org/oxycblt/auxio/music/user/DeviceLibraryTest.kt
new file mode 100644
index 000000000..cdbbc6af9
--- /dev/null
+++ b/app/src/test/java/org/oxycblt/auxio/music/user/DeviceLibraryTest.kt
@@ -0,0 +1,180 @@
+/*
+ * Copyright (c) 2023 Auxio Project
+ * DeviceLibraryTest.kt is part of Auxio.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+ 
+package org.oxycblt.auxio.music.user
+
+import io.mockk.every
+import io.mockk.mockk
+import io.mockk.verify
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNotEquals
+import org.junit.Test
+import org.oxycblt.auxio.music.Music
+import org.oxycblt.auxio.music.MusicType
+import org.oxycblt.auxio.music.device.AlbumImpl
+import org.oxycblt.auxio.music.device.ArtistImpl
+import org.oxycblt.auxio.music.device.DeviceLibraryImpl
+import org.oxycblt.auxio.music.device.GenreImpl
+import org.oxycblt.auxio.music.device.SongImpl
+
+class DeviceLibraryTest {
+
+    @Test
+    fun deviceLibrary_withSongs() {
+        val songUidA = Music.UID.auxio(MusicType.SONGS)
+        val songUidB = Music.UID.auxio(MusicType.SONGS)
+        val songA =
+            mockk<SongImpl> {
+                every { uid } returns songUidA
+                every { durationMs } returns 0
+                every { finalize() } returns this
+            }
+        val songB =
+            mockk<SongImpl> {
+                every { uid } returns songUidB
+                every { durationMs } returns 1
+                every { finalize() } returns this
+            }
+        val deviceLibrary = DeviceLibraryImpl(listOf(songA, songB), listOf(), listOf(), listOf())
+        verify {
+            songA.finalize()
+            songB.finalize()
+        }
+        val foundSongA = deviceLibrary.findSong(songUidA)!!
+        assertEquals(songUidA, foundSongA.uid)
+        assertEquals(0L, foundSongA.durationMs)
+        val foundSongB = deviceLibrary.findSong(songUidB)!!
+        assertEquals(songUidB, foundSongB.uid)
+        assertEquals(1L, foundSongB.durationMs)
+    }
+
+    @Test
+    fun deviceLibrary_withAlbums() {
+        val albumUidA = Music.UID.auxio(MusicType.ALBUMS)
+        val albumUidB = Music.UID.auxio(MusicType.ALBUMS)
+        val albumA =
+            mockk<AlbumImpl> {
+                every { uid } returns albumUidA
+                every { durationMs } returns 0
+                every { finalize() } returns this
+            }
+        val albumB =
+            mockk<AlbumImpl> {
+                every { uid } returns albumUidB
+                every { durationMs } returns 1
+                every { finalize() } returns this
+            }
+        val deviceLibrary = DeviceLibraryImpl(listOf(), listOf(albumA, albumB), listOf(), listOf())
+        verify {
+            albumA.finalize()
+            albumB.finalize()
+        }
+        val foundAlbumA = deviceLibrary.findAlbum(albumUidA)!!
+        assertEquals(albumUidA, foundAlbumA.uid)
+        assertEquals(0L, foundAlbumA.durationMs)
+        val foundAlbumB = deviceLibrary.findAlbum(albumUidB)!!
+        assertEquals(albumUidB, foundAlbumB.uid)
+        assertEquals(1L, foundAlbumB.durationMs)
+    }
+
+    @Test
+    fun deviceLibrary_withArtists() {
+        val artistUidA = Music.UID.auxio(MusicType.ARTISTS)
+        val artistUidB = Music.UID.auxio(MusicType.ARTISTS)
+        val artistA =
+            mockk<ArtistImpl> {
+                every { uid } returns artistUidA
+                every { durationMs } returns 0
+                every { finalize() } returns this
+            }
+        val artistB =
+            mockk<ArtistImpl> {
+                every { uid } returns artistUidB
+                every { durationMs } returns 1
+                every { finalize() } returns this
+            }
+        val deviceLibrary =
+            DeviceLibraryImpl(listOf(), listOf(), listOf(artistA, artistB), listOf())
+        verify {
+            artistA.finalize()
+            artistB.finalize()
+        }
+        val foundArtistA = deviceLibrary.findArtist(artistUidA)!!
+        assertEquals(artistUidA, foundArtistA.uid)
+        assertEquals(0L, foundArtistA.durationMs)
+        val foundArtistB = deviceLibrary.findArtist(artistUidB)!!
+        assertEquals(artistUidB, foundArtistB.uid)
+        assertEquals(1L, foundArtistB.durationMs)
+    }
+
+    @Test
+    fun deviceLibrary_withGenres() {
+        val genreUidA = Music.UID.auxio(MusicType.GENRES)
+        val genreUidB = Music.UID.auxio(MusicType.GENRES)
+        val genreA =
+            mockk<GenreImpl> {
+                every { uid } returns genreUidA
+                every { durationMs } returns 0
+                every { finalize() } returns this
+            }
+        val genreB =
+            mockk<GenreImpl> {
+                every { uid } returns genreUidB
+                every { durationMs } returns 1
+                every { finalize() } returns this
+            }
+        val deviceLibrary = DeviceLibraryImpl(listOf(), listOf(), listOf(), listOf(genreA, genreB))
+        verify {
+            genreA.finalize()
+            genreB.finalize()
+        }
+        val foundGenreA = deviceLibrary.findGenre(genreUidA)!!
+        assertEquals(genreUidA, foundGenreA.uid)
+        assertEquals(0L, foundGenreA.durationMs)
+        val foundGenreB = deviceLibrary.findGenre(genreUidB)!!
+        assertEquals(genreUidB, foundGenreB.uid)
+        assertEquals(1L, foundGenreB.durationMs)
+    }
+
+    @Test
+    fun deviceLibrary_equals() {
+        val songA =
+            mockk<SongImpl> {
+                every { uid } returns Music.UID.auxio(MusicType.SONGS)
+                every { finalize() } returns this
+            }
+        val songB =
+            mockk<SongImpl> {
+                every { uid } returns Music.UID.auxio(MusicType.SONGS)
+                every { finalize() } returns this
+            }
+        val album =
+            mockk<AlbumImpl> {
+                every { uid } returns mockk()
+                every { finalize() } returns this
+            }
+
+        val deviceLibraryA = DeviceLibraryImpl(listOf(songA), listOf(album), listOf(), listOf())
+        val deviceLibraryB = DeviceLibraryImpl(listOf(songA), listOf(), listOf(), listOf())
+        val deviceLibraryC = DeviceLibraryImpl(listOf(songB), listOf(album), listOf(), listOf())
+        assertEquals(deviceLibraryA, deviceLibraryB)
+        assertEquals(deviceLibraryA.hashCode(), deviceLibraryA.hashCode())
+        assertNotEquals(deviceLibraryA, deviceLibraryC)
+        assertNotEquals(deviceLibraryA.hashCode(), deviceLibraryC.hashCode())
+    }
+}