meeting-assistant/MeetingAssistant.Tests/RollingAudioBufferTests.cs

using MeetingAssistant.Recording;
using NAudio.Wave;

namespace MeetingAssistant.Tests;

public sealed class RollingAudioBufferTests
{
    [Fact]
    public void TryExtractWavReturnsRequestedRangeFromBufferedPcm()
    {
        var buffer = new RollingAudioBuffer(TimeSpan.FromSeconds(10));
        buffer.Append(new AudioChunk(Samples(0, 1, 2, 3), SampleRate: 2, Channels: 1));
        buffer.Append(new AudioChunk(Samples(4, 5, 6, 7), SampleRate: 2, Channels: 1));

        var wav = buffer.TryExtractWav(TimeSpan.FromSeconds(1), TimeSpan.FromSeconds(3));

        using var reader = new WaveFileReader(new MemoryStream(wav));
        var bytes = new byte[reader.Length];
        var read = reader.Read(bytes, 0, bytes.Length);
        Assert.Equal(bytes.Length, read);
        Assert.Equal(Samples(2, 3, 4, 5), bytes);
    }

    [Fact]
    public void TryExtractWavDropsAudioOutsideRetentionWindow()
    {
        var buffer = new RollingAudioBuffer(TimeSpan.FromSeconds(1));
        buffer.Append(new AudioChunk(Samples(0, 1), SampleRate: 1, Channels: 1));
        buffer.Append(new AudioChunk(Samples(2, 3), SampleRate: 1, Channels: 1));

        var wav = buffer.TryExtractWav(TimeSpan.Zero, TimeSpan.FromSeconds(1));

        Assert.Empty(wav);
    }

    private static byte[] Samples(params short[] samples)
    {
        var bytes = new byte[samples.Length * sizeof(short)];
        Buffer.BlockCopy(samples, 0, bytes, 0, bytes.Length);
        return bytes;
    }
}