Add an end-to-end subtitle delay playback test

app/src/test/java/com/github/damontecres/wholphin/services/SubtitleDelayPlaybackTest.kt

@@ -0,0 +1,186 @@
+@file:OptIn(markerClass = [UnstableApi::class])
+
+package com.github.damontecres.wholphin.services
+
+import android.content.Context
+import android.net.Uri
+import androidx.annotation.OptIn
+import androidx.media3.common.C
+import androidx.media3.common.MediaItem
+import androidx.media3.common.MimeTypes
+import androidx.media3.common.Player
+import androidx.media3.common.text.CueGroup
+import androidx.media3.common.util.UnstableApi
+import androidx.media3.exoplayer.ExoPlayer
+import androidx.media3.exoplayer.source.DefaultMediaSourceFactory
+import androidx.media3.test.utils.FakeClock
+import androidx.media3.test.utils.robolectric.CapturingRenderersFactory
+import androidx.media3.test.utils.robolectric.TestPlayerRunHelper.play
+import androidx.media3.test.utils.robolectric.TestPlayerRunHelper.run
+import androidx.test.core.app.ApplicationProvider
+import org.junit.After
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertTrue
+import org.junit.Before
+import org.junit.Rule
+import org.junit.Test
+import org.junit.rules.TemporaryFolder
+import org.junit.runner.RunWith
+import org.robolectric.RobolectricTestRunner
+import org.robolectric.annotation.Config
+import java.io.File
+import java.nio.ByteBuffer
+import java.nio.ByteOrder
+import kotlin.math.abs
+import kotlin.time.Duration
+import kotlin.time.Duration.Companion.milliseconds
+import kotlin.time.Duration.Companion.seconds
+
+/**
+ * Plays a short audio file with a sideloaded SRT through a real [ExoPlayer] and checks when the
+ * subtitles appear for a given delay, and that playback still ends when the media does.
+ */
+@RunWith(RobolectricTestRunner::class)
+@Config(manifest = Config.NONE, sdk = [30])
+class SubtitleDelayPlaybackTest {
+    @get:Rule val folder = TemporaryFolder()
+
+    private val context = ApplicationProvider.getApplicationContext<Context>()
+    private val clock = FakeClock(true)
+    private val shownCues = mutableListOf<Pair<String, Long>>()
+    private val playbackStates = mutableListOf<Int>()
+    private lateinit var player: ExoPlayer
+
+    @Before
+    fun setUp() {
+        player =
+            ExoPlayer
+                .Builder(context, SubtitleDelayRenderersFactory(CapturingRenderersFactory(context, clock)))
+                .setMediaSourceFactory(DefaultMediaSourceFactory(context))
+                .setClock(clock)
+                .build()
+        player.addListener(
+            object : Player.Listener {
+                override fun onCues(cueGroup: CueGroup) {
+                    cueGroup.cues.firstOrNull()?.let { shownCues.add(it.text.toString() to player.currentPosition) }
+                }
+
+                override fun onPlaybackStateChanged(playbackState: Int) {
+                    playbackStates.add(playbackState)
+                }
+            },
+        )
+        player.setMediaItem(mediaItem())
+        player.prepare()
+        // Subtitles never hold up playback, so let the sideloaded file load before playing
+        run(player).untilState(Player.STATE_READY)
+        run(player).untilLoadingIs(false)
+        assertTrue(player.currentTracks.isTypeSelected(C.TRACK_TYPE_TEXT))
+    }
+
+    @After
+    fun tearDown() {
+        player.release()
+    }
+
+    @Test
+    fun positiveDelayShowsSubtitlesLaterAndPlaybackEndsOnTime() {
+        player.applySubtitleDelay(2.seconds)
+        val playStartMs = clock.elapsedRealtime()
+
+        play(player).untilState(Player.STATE_ENDED)
+
+        assertShownAt("First" to 3.seconds)
+        val playedMs = clock.elapsedRealtime() - playStartMs
+        assertTrue(
+            "ended after $playedMs ms of playback, expected $DURATION",
+            abs(playedMs - DURATION.inWholeMilliseconds) <= TOLERANCE_MS,
+        )
+    }
+
+    @Test
+    fun negativeDelayShowsSubtitlesEarlier() {
+        player.applySubtitleDelay((-500).milliseconds)
+
+        play(player).untilState(Player.STATE_ENDED)
+
+        assertShownAt("First" to 500.milliseconds, "Last" to 2.seconds)
+    }
+
+    @Test
+    fun changingTheDelayWhilePlayingRetimesWithoutRebuffering() {
+        play(player).untilPosition(0, 500)
+        player.applySubtitleDelay(1.seconds)
+
+        play(player).untilState(Player.STATE_ENDED)
+
+        assertShownAt("First" to 2.seconds, "Last" to 3_500.milliseconds)
+        assertEquals(listOf(Player.STATE_BUFFERING, Player.STATE_READY, Player.STATE_ENDED), playbackStates)
+    }
+
+    private fun assertShownAt(vararg expected: Pair<String, Duration>) {
+        assertEquals(expected.map { it.first }, shownCues.map { it.first })
+        expected.zip(shownCues).forEach { (want, got) ->
+            assertTrue(
+                "${want.first} shown at ${got.second} ms, expected ${want.second}",
+                abs(got.second - want.second.inWholeMilliseconds) <= TOLERANCE_MS,
+            )
+        }
+    }
+
+    private fun mediaItem(): MediaItem {
+        val audio = folder.newFile("silence.wav").apply { writeBytes(silentWav()) }
+        val subtitles = folder.newFile("subtitles.srt").apply { writeText(SRT) }
+        return MediaItem
+            .Builder()
+            .setUri(Uri.fromFile(audio))
+            .setSubtitleConfigurations(
+                listOf(
+                    MediaItem.SubtitleConfiguration
+                        .Builder(Uri.fromFile(subtitles))
+                        .setMimeType(MimeTypes.APPLICATION_SUBRIP)
+                        .setLanguage("en")
+                        .setSelectionFlags(C.SELECTION_FLAG_DEFAULT)
+                        .build(),
+                ),
+            ).build()
+    }
+
+    /** A mono 16-bit PCM WAV file of silence lasting [DURATION] */
+    private fun silentWav(): ByteArray {
+        val dataSize = (SAMPLE_RATE * DURATION.inWholeMilliseconds / 1000 * 2).toInt()
+        return ByteBuffer
+            .allocate(44 + dataSize)
+            .order(ByteOrder.LITTLE_ENDIAN)
+            .put("RIFF".toByteArray())
+            .putInt(36 + dataSize)
+            .put("WAVEfmt ".toByteArray())
+            .putInt(16)
+            .putShort(1)
+            .putShort(1)
+            .putInt(SAMPLE_RATE)
+            .putInt(SAMPLE_RATE * 2)
+            .putShort(2)
+            .putShort(16)
+            .put("data".toByteArray())
+            .putInt(dataSize)
+            .array()
+    }
+
+    private companion object {
+        const val SAMPLE_RATE = 8_000
+        const val TOLERANCE_MS = 100L
+        val DURATION = 4.seconds
+        val SRT =
+            """
+            1
+            00:00:01,000 --> 00:00:02,000
+            First
+
+            2
+            00:00:02,500 --> 00:00:03,500
+            Last
+
+            """.trimIndent()
+    }
+}