Coordinate matching audio source delivery in regression test

MeetingAssistant.Tests/AudioMixingTests.cs

@@ -58,14 +58,21 @@ public sealed class AudioMixingTests
     [Fact]
     public async Task CompositeAudioSourceWaitsForMatchingStreamsBeforeMixing()
     {
-        var microphone = new DelayedAudioSource(TimeSpan.Zero, Pcm16(2_000));
-        var system = new DelayedAudioSource(TimeSpan.FromMilliseconds(100), Pcm16(10_000));
+        var microphone = new ControlledAudioSource(Pcm16(2_000));
+        var system = new ControlledAudioSource(Pcm16(10_000));
         var source = CreateSource(microphone, system);
+        using var cancellation = new CancellationTokenSource(TimeSpan.FromSeconds(5));
+        await using var chunks = source.CaptureAsync(cancellation.Token).GetAsyncEnumerator(cancellation.Token);
+        var nextChunk = chunks.MoveNextAsync().AsTask();
 
-        var chunks = await ReadChunks(source);
+        microphone.Release();
+        await microphone.WaitUntilDeliveredAsync();
+        Assert.False(nextChunk.IsCompleted);
 
-        var chunk = Assert.Single(chunks);
-        Assert.Equal(12_000, BitConverter.ToInt16(chunk.Pcm));
+        system.Release();
+        Assert.True(await nextChunk);
+        Assert.Equal(12_000, BitConverter.ToInt16(chunks.Current.Pcm));
+        Assert.False(await chunks.MoveNextAsync());
     }
 
     [Fact]
@@ -187,6 +194,30 @@ public sealed class AudioMixingTests
         }
     }
 
+    private sealed class ControlledAudioSource : IMeetingAudioSource
+    {
+        private readonly AudioChunk chunk;
+        private readonly TaskCompletionSource release = new(TaskCreationOptions.RunContinuationsAsynchronously);
+        private readonly TaskCompletionSource delivered = new(TaskCreationOptions.RunContinuationsAsynchronously);
+
+        public ControlledAudioSource(byte[] pcm)
+        {
+            chunk = new AudioChunk(pcm, 16000, 1);
+        }
+
+        public void Release() => release.TrySetResult();
+
+        public Task WaitUntilDeliveredAsync() => delivered.Task.WaitAsync(TimeSpan.FromSeconds(5));
+
+        public async IAsyncEnumerable<AudioChunk> CaptureAsync(
+            [System.Runtime.CompilerServices.EnumeratorCancellation] CancellationToken cancellationToken)
+        {
+            await release.Task.WaitAsync(cancellationToken);
+            yield return chunk;
+            delivered.TrySetResult();
+        }
+    }
+
     private sealed class DelayedAudioSource : IMeetingAudioSource
     {
         private readonly TimeSpan delay;