diff --git a/app/src/test/kotlin/com/subtracks/data/source/subsonic/SubsonicClientTest.kt b/app/src/test/kotlin/com/subtracks/data/source/subsonic/SubsonicClientTest.kt
new file mode 100644
index 00000000..0474b874
--- /dev/null
+++ b/app/src/test/kotlin/com/subtracks/data/source/subsonic/SubsonicClientTest.kt
@@ -0,0 +1,92 @@
+package com.subtracks.data.source.subsonic
+
+import okhttp3.OkHttpClient
+import okhttp3.mockwebserver.MockResponse
+import okhttp3.mockwebserver.MockWebServer
+import org.junit.After
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNotNull
+import org.junit.Assert.assertNull
+import org.junit.Assert.assertThrows
+import org.junit.Before
+import org.junit.Test
+
+class SubsonicClientTest {
+    private lateinit var server: MockWebServer
+
+    @Before
+    fun setUp() {
+        server = MockWebServer()
+        server.start()
+    }
+
+    @After
+    fun tearDown() {
+        server.shutdown()
+    }
+
+    private fun client(tokenAuth: Boolean) = SubsonicClient(
+        baseUrl = server.url("/"),
+        username = "guest",
+        password = "secret",
+        useTokenAuth = tokenAuth,
+        http = OkHttpClient(),
+    )
+
+    @Test
+    fun tokenAuthSendsSaltAndHash() {
+        server.enqueue(MockResponse().setBody("<subsonic-response status=\"ok\" version=\"1.16.1\"/>"))
+
+        client(tokenAuth = true).get("ping")
+
+        val url = server.takeRequest().requestUrl!!
+        assertEquals("/rest/ping.view", url.encodedPath)
+        assertEquals("guest", url.queryParameter("u"))
+        assertEquals("subtracks", url.queryParameter("c"))
+        assertNotNull(url.queryParameter("s"))
+        assertNotNull(url.queryParameter("t"))
+        assertNull(url.queryParameter("p"))
+    }
+
+    @Test
+    fun plaintextAuthSendsPassword() {
+        server.enqueue(MockResponse().setBody("<subsonic-response status=\"ok\" version=\"1.16.1\"/>"))
+
+        client(tokenAuth = false).get("ping")
+
+        val url = server.takeRequest().requestUrl!!
+        assertEquals("secret", url.queryParameter("p"))
+        assertNull(url.queryParameter("t"))
+    }
+
+    @Test
+    fun paramsAreForwarded() {
+        server.enqueue(MockResponse().setBody("<subsonic-response status=\"ok\" version=\"1.16.1\"/>"))
+
+        client(tokenAuth = true).get("getCoverArt", mapOf("id" to "cov", "size" to "256"))
+
+        val url = server.takeRequest().requestUrl!!
+        assertEquals("cov", url.queryParameter("id"))
+        assertEquals("256", url.queryParameter("size"))
+    }
+
+    @Test
+    fun failedStatusThrowsWithCode() {
+        server.enqueue(
+            MockResponse().setBody(
+                "<subsonic-response status=\"failed\"><error code=\"40\" message=\"Wrong username\"/></subsonic-response>",
+            ),
+        )
+
+        val error = assertThrows(SubsonicException::class.java) { client(tokenAuth = true).get("ping") }
+        assertEquals(40, error.code)
+        assertEquals("Wrong username", error.message)
+    }
+
+    @Test
+    fun nonSubsonicResponseThrows() {
+        server.enqueue(MockResponse().setBody("<html><body>Sign in</body></html>"))
+
+        assertThrows(SubsonicException::class.java) { client(tokenAuth = true).get("ping") }
+    }
+}
diff --git a/app/src/test/kotlin/com/subtracks/data/source/subsonic/SubsonicSourceTest.kt b/app/src/test/kotlin/com/subtracks/data/source/subsonic/SubsonicSourceTest.kt
new file mode 100644
index 00000000..ab51aac0
--- /dev/null
+++ b/app/src/test/kotlin/com/subtracks/data/source/subsonic/SubsonicSourceTest.kt
@@ -0,0 +1,72 @@
+package com.subtracks.data.source.subsonic
+
+import kotlinx.coroutines.runBlocking
+import okhttp3.OkHttpClient
+import okhttp3.mockwebserver.Dispatcher
+import okhttp3.mockwebserver.MockResponse
+import okhttp3.mockwebserver.MockWebServer
+import okhttp3.mockwebserver.RecordedRequest
+import org.junit.After
+import org.junit.Assert.assertEquals
+import org.junit.Before
+import org.junit.Test
+
+class SubsonicSourceTest {
+    private lateinit var server: MockWebServer
+
+    @Before
+    fun setUp() {
+        server = MockWebServer()
+        server.start()
+    }
+
+    @After
+    fun tearDown() {
+        server.shutdown()
+    }
+
+    @Test
+    fun getSongsFallsBackToAlbumsWhenEmptySearchUnsupported() = runBlocking {
+        server.dispatcher = object : Dispatcher() {
+            override fun dispatch(request: RecordedRequest): MockResponse = when {
+                request.path?.startsWith("/rest/search3.view") == true ->
+                    MockResponse().setBody(failed(10, "Required parameter is missing"))
+
+                request.path?.startsWith("/rest/getAlbumList2.view") == true ->
+                    MockResponse().setBody(ALBUM_LIST)
+
+                request.path?.startsWith("/rest/getAlbum.view") == true ->
+                    MockResponse().setBody(ALBUM)
+
+                else -> MockResponse().setResponseCode(404)
+            }
+        }
+        val source = SubsonicSource(1, client())
+
+        assertEquals(listOf("s1", "s2"), source.getSongs().map { it.id })
+    }
+
+    private fun client() = SubsonicClient(
+        baseUrl = server.url("/"),
+        username = "u",
+        password = "p",
+        useTokenAuth = false,
+        http = OkHttpClient(),
+    )
+
+    private fun failed(code: Int, message: String) =
+        "<subsonic-response status=\"failed\"><error code=\"$code\" message=\"$message\"/></subsonic-response>"
+
+    private companion object {
+        const val ALBUM_LIST =
+            "<subsonic-response status=\"ok\" version=\"1.16.1\"><albumList2>" +
+                "<album id=\"al1\" name=\"Album\" artist=\"Artist\" artistId=\"ar1\" songCount=\"2\"/>" +
+                "</albumList2></subsonic-response>"
+
+        const val ALBUM =
+            "<subsonic-response status=\"ok\" version=\"1.16.1\"><album id=\"al1\" name=\"Album\" artist=\"Artist\" artistId=\"ar1\">" +
+                "<song id=\"s1\" title=\"One\" albumId=\"al1\" artistId=\"ar1\" track=\"1\"/>" +
+                "<song id=\"s2\" title=\"Two\" albumId=\"al1\" artistId=\"ar1\" track=\"2\"/>" +
+                "</album></subsonic-response>"
+    }
+}
diff --git a/app/src/test/kotlin/com/subtracks/data/source/subsonic/SubsonicXmlTest.kt b/app/src/test/kotlin/com/subtracks/data/source/subsonic/SubsonicXmlTest.kt
new file mode 100644
index 00000000..437f4edf
--- /dev/null
+++ b/app/src/test/kotlin/com/subtracks/data/source/subsonic/SubsonicXmlTest.kt
@@ -0,0 +1,94 @@
+package com.subtracks.data.source.subsonic
+
+import javax.xml.parsers.DocumentBuilderFactory
+import org.junit.Assert.assertEquals
+import org.junit.Test
+import org.w3c.dom.Document
+
+class SubsonicXmlTest {
+    private fun parse(xml: String): Document =
+        DocumentBuilderFactory.newInstance().newDocumentBuilder()
+            .parse(xml.byteInputStream(Charsets.UTF_8))
+
+    @Test
+    fun mapsArtists() {
+        val document = parse(
+            """
+            <subsonic-response status="ok">
+              <artists>
+                <artist id="ar1" name="Radiohead" albumCount="9" starred="2020-01-02T03:04:05.000Z"/>
+                <artist id="ar2" name="Portishead" albumCount="3"/>
+              </artists>
+            </subsonic-response>
+            """.trimIndent(),
+        )
+
+        val artists = SubsonicXml.artists(7, document)
+
+        assertEquals(2, artists.size)
+        assertEquals("Radiohead", artists[0].name)
+        assertEquals(7L, artists[0].sourceId)
+        assertEquals(9L, artists[0].albumCount)
+        assertEquals(1577934245L, artists[0].starred)
+        assertEquals(null, artists[1].starred)
+    }
+
+    @Test
+    fun mapsAlbumList() {
+        val document = parse(
+            """
+            <subsonic-response status="ok">
+              <albumList2>
+                <album id="al1" name="OK Computer" artist="Radiohead" artistId="ar1" created="1997-05-21T00:00:00.000Z" songCount="12" coverArt="al1"/>
+                <album id="al2" name="Kid A" artist="Radiohead" artistId="ar1" created="2000-10-02T00:00:00.000Z" songCount="10" coverArt="al2"/>
+              </albumList2>
+            </subsonic-response>
+            """.trimIndent(),
+        )
+
+        val albums = SubsonicXml.albums(1, document)
+
+        assertEquals(2, albums.size)
+        assertEquals("OK Computer", albums[0].name)
+        assertEquals("Kid A", albums[1].name)
+        assertEquals("ar1", albums[0].artistId)
+        assertEquals("Radiohead", albums[0].albumArtist)
+        assertEquals(12L, albums[0].songCount)
+    }
+
+    @Test
+    fun parsesTimestampsWithFractionsAndOffsets() {
+        assertEquals(1789906657L, IsoDate.parse("2026-09-20T12:17:37.370827413Z"))
+        assertEquals(1789906657L, IsoDate.parse("2026-09-20T12:17:37.370Z"))
+        assertEquals(1789906657L, IsoDate.parse("2026-09-20T12:17:37Z"))
+        assertEquals(1789906657L, IsoDate.parse("2026-09-20T12:17:37"))
+        assertEquals(1789906657L, IsoDate.parse("2026-09-20T14:17:37.370827413+02:00"))
+        assertEquals(null, IsoDate.parse("not a date"))
+    }
+
+    @Test
+    fun mapsSongsAndPlaylistEntries() {
+        val document = parse(
+            """
+            <subsonic-response status="ok">
+              <searchResult3>
+                <song id="sg2" title="Idioteque" artist="Radiohead" album="Kid A" albumId="al2" artistId="ar1" duration="300" track="8" discNumber="1"/>
+              </searchResult3>
+              <playlist id="pl1" name="Favourites" songCount="1" created="2021-02-03T04:05:06.000Z">
+                <entry id="sg1" title="Everything In Its Right Place" artist="Radiohead" album="Kid A" albumId="al2" artistId="ar1" duration="251" track="1" discNumber="1"/>
+              </playlist>
+            </subsonic-response>
+            """.trimIndent(),
+        )
+
+        val songs = SubsonicXml.songs(1, document)
+        val entries = SubsonicXml.playlistSongs(1, "pl1", document)
+
+        assertEquals(1, songs.size)
+        assertEquals("Idioteque", songs[0].title)
+        assertEquals(300L, songs[0].duration)
+        assertEquals(0L, entries[0].position)
+        assertEquals("sg1", entries[0].songId)
+        assertEquals(251L, SubsonicXml.song(1, document.getElementsByTagName("entry").item(0) as org.w3c.dom.Element).duration)
+    }
+}
diff --git a/app/src/test/kotlin/com/subtracks/data/sync/SyncServiceTest.kt b/app/src/test/kotlin/com/subtracks/data/sync/SyncServiceTest.kt
new file mode 100644
index 00000000..ecc94942
--- /dev/null
+++ b/app/src/test/kotlin/com/subtracks/data/sync/SyncServiceTest.kt
@@ -0,0 +1,171 @@
+package com.subtracks.data.sync
+
+import android.content.Context
+import androidx.room3.Room
+import androidx.test.core.app.ApplicationProvider
+import androidx.sqlite.driver.bundled.BundledSQLiteDriver
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import com.subtracks.data.db.SubtracksDatabase
+import com.subtracks.data.model.Album
+import com.subtracks.data.model.Artist
+import com.subtracks.data.model.Playlist
+import com.subtracks.data.model.PlaylistSong
+import com.subtracks.data.model.Song
+import com.subtracks.data.model.Source
+import com.subtracks.data.source.MusicSource
+import kotlinx.coroutines.flow.first
+import kotlinx.coroutines.test.runTest
+import org.junit.After
+import org.junit.Assert.assertEquals
+import org.junit.Before
+import org.junit.Test
+import org.junit.runner.RunWith
+
+@RunWith(AndroidJUnit4::class)
+class SyncServiceTest {
+    private lateinit var db: SubtracksDatabase
+
+    @Before
+    fun setUp() {
+        val context = ApplicationProvider.getApplicationContext<Context>()
+        db = Room.inMemoryDatabaseBuilder(context, SubtracksDatabase::class.java)
+            .setDriver(BundledSQLiteDriver())
+            .build()
+    }
+
+    @After
+    fun tearDown() {
+        db.close()
+    }
+
+    @Test
+    fun syncInsertsAndPrunesRemovedRows() = runTest {
+        insertSource()
+        val source = FakeMusicSource(
+            artists = listOf(artist("a1"), artist("a2")),
+            albums = listOf(album("al1")),
+            songs = listOf(song("s1"), song("s2")),
+            playlists = listOf(playlist("p1")),
+            playlistSongs = listOf(PlaylistSong(1, "p1", "s1", 0)),
+        )
+
+        SyncService(db, source).sync()
+
+        assertEquals(2, db.libraryDao().artists(1).first().size)
+        assertEquals(2, db.libraryDao().songs(1).first().size)
+        assertEquals(1, db.libraryDao().songsByPlaylist(1, "p1").first().size)
+
+        source.artists = listOf(artist("a1"))
+        source.songs = listOf(song("s1"))
+
+        SyncService(db, source).sync()
+
+        assertEquals(listOf("a1"), db.libraryDao().artists(1).first().map { it.id })
+        assertEquals(listOf("s1"), db.libraryDao().songs(1).first().map { it.id })
+    }
+
+    @Test
+    fun searchIndexMatchesSubstrings() = runTest {
+        insertSource()
+        val source = FakeMusicSource(
+            artists = listOf(artist("a1", name = "Radiohead")),
+            songs = listOf(song("s1")),
+        )
+
+        SyncService(db, source).sync()
+
+        val results = db.searchDao().search("1", "adio", 10)
+        assertEquals(1, results.size)
+        assertEquals("a1", results.single().itemId)
+        assertEquals("artist", results.single().type)
+    }
+
+    @Test
+    fun searchIgnoresTooShortQueries() = runTest {
+        insertSource()
+        SyncService(db, FakeMusicSource(artists = listOf(artist("a1", name = "Radiohead")))).sync()
+
+        assertEquals(0, db.searchDao().search("1", "ad", 10).size)
+        assertEquals(0, db.searchDao().search("1", "", 10).size)
+        assertEquals(1, db.searchDao().search("1", "adi", 10).size)
+    }
+
+    @Test
+    fun syncUpdatesExistingRows() = runTest {
+        insertSource()
+        val source = FakeMusicSource(artists = listOf(artist("a1", name = "Old")))
+
+        SyncService(db, source).sync()
+        assertEquals("Old", db.libraryDao().artists(1).first().single().name)
+
+        source.artists = listOf(artist("a1", name = "New"))
+        SyncService(db, source).sync()
+
+        assertEquals("New", db.libraryDao().artists(1).first().single().name)
+    }
+
+    private suspend fun insertSource() {
+        db.sourcesDao().upsertSource(
+            Source(id = 1, name = "test", address = "http://localhost", isActive = true, createdAt = 0),
+        )
+    }
+
+    private fun artist(id: String, name: String = "Artist $id") =
+        Artist(sourceId = 1, id = id, name = name, albumCount = 1, starred = null)
+
+    private fun album(id: String) = Album(
+        sourceId = 1,
+        id = id,
+        artistId = "a1",
+        name = "Album $id",
+        albumArtist = "Artist",
+        created = 0,
+        coverArt = null,
+        genre = null,
+        year = null,
+        starred = null,
+        songCount = 1,
+        frequentRank = null,
+        recentRank = null,
+    )
+
+    private fun song(id: String) = Song(
+        sourceId = 1,
+        id = id,
+        albumId = "al1",
+        artistId = "a1",
+        title = "Song $id",
+        album = "Album",
+        artist = "Artist",
+        duration = 100,
+        track = 1,
+        disc = 1,
+        starred = null,
+        genre = null,
+    )
+
+    private fun playlist(id: String) =
+        Playlist(sourceId = 1, id = id, name = "Playlist $id", comment = null, coverArt = null, songCount = 1, created = 0)
+}
+
+private class FakeMusicSource(
+    var artists: List<Artist> = emptyList(),
+    var albums: List<Album> = emptyList(),
+    var songs: List<Song> = emptyList(),
+    var playlists: List<Playlist> = emptyList(),
+    var playlistSongs: List<PlaylistSong> = emptyList(),
+) : MusicSource {
+    override val id: Long = 1
+
+    override suspend fun ping() = Unit
+
+    override suspend fun getArtists(): List<Artist> = artists
+
+    override suspend fun getAlbums(): List<Album> = albums
+
+    override suspend fun getSongs(): List<Song> = songs
+
+    override suspend fun getPlaylists(): List<Playlist> = playlists
+
+    override suspend fun getPlaylistSongs(playlists: List<Playlist>): List<PlaylistSong> = playlistSongs
+}
diff --git a/app/src/test/kotlin/com/subtracks/ui/HelloScreenshotTest.kt b/app/src/test/kotlin/com/subtracks/ui/HelloScreenshotTest.kt
index 35400aec..1e3c6993 100644
--- a/app/src/test/kotlin/com/subtracks/ui/HelloScreenshotTest.kt
+++ b/app/src/test/kotlin/com/subtracks/ui/HelloScreenshotTest.kt
@@ -1,7 +1,7 @@
 package com.subtracks.ui
 
 import androidx.activity.ComponentActivity
-import androidx.compose.ui.test.junit4.createAndroidComposeRule
+import androidx.compose.ui.test.junit4.v2.createAndroidComposeRule
 import androidx.compose.ui.test.onRoot
 import androidx.test.ext.junit.runners.AndroidJUnit4
 import com.github.takahirom.roborazzi.RobolectricDeviceQualifiers