Easy way to simulate a player exception in ExoPlayer

FirstFailureMediaFactory.kt

package com.bandlab.media.player

import androidx.media3.common.MediaItem
import androidx.media3.datasource.TransferListener
import androidx.media3.exoplayer.analytics.PlayerId
import androidx.media3.exoplayer.source.MediaSource
import java.util.Random

class FirstFailureMediaSourceFactory(
    private val delegate: MediaSource.Factory,
) : MediaSource.Factory by delegate {

    override fun createMediaSource(mediaItem: MediaItem): MediaSource {
        val originalSource = delegate.createMediaSource(mediaItem)
        return FirstFailureMediaSource(originalSource)
    }
}

object MediaSourceFailureController {

    private var counter: Int = 0

    fun shouldError(): Boolean {
        counter++
        if (counter >= 5) {
            counter = 0
            return true
        }
        return false
    }
}

private class FirstFailureMediaSource(private val delegate: MediaSource) : MediaSource by delegate {

    override fun prepareSource(
        caller: MediaSource.MediaSourceCaller,
        mediaTransferListener: TransferListener?,
        playerId: PlayerId,
    ) {
        if (MediaSourceFailureController.shouldError()) {
            // We throw immediately when the player tries to prepare the source
            // This is caught by ExoPlayerImplInternal and wrapped as TYPE_UNEXPECTED
            throw NullPointerException("androidx.media3.decoder.mpeghaudio.MpeghAudioSink")
        } else {
            delegate.prepareSource(caller, mediaTransferListener, playerId)
        }
    }
}

USAGE.md

Just set it as media source factory

ExoPlayer.Builder(context)
  .setMediaSourceFactory(FirstFailureMediaFactory(realMediaSourceFactory))
  ....
  .build()