add a transcoding test

related #378

transcode/transcode_test.go

@@ -0,0 +1,53 @@
+package transcode_test
+
+import (
+	"bytes"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"os/exec"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+	"go.senan.xyz/gonic/transcode"
+)
+
+// TestTranscode starts a web server that transcodes a 5s FLAC file to PCM audio. A client
+// consumes the result over a 5 second period.
+func TestTranscode(t *testing.T) {
+	t.Parallel()
+
+	if _, err := exec.LookPath("ffmpeg"); err != nil {
+		t.Skip("ffmpeg not in PATH")
+	}
+
+	tr := transcode.NewFFmpegTranscoder()
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		require.NoError(t, tr.Transcode(r.Context(), transcode.PCM16le, "testdata/5s.flac", w))
+		f, ok := w.(http.Flusher)
+		require.True(t, ok)
+		f.Flush()
+	}))
+	defer server.Close()
+
+	resp, err := server.Client().Get(server.URL)
+	require.NoError(t, err)
+	defer resp.Body.Close()
+
+	const sampleRate, bytesPerSample, numChannels = 48_000, 2, 2
+	const bytesPerSec = sampleRate * bytesPerSample * numChannels
+
+	var buf bytes.Buffer
+	for {
+		n, err := io.Copy(&buf, io.LimitReader(resp.Body, bytesPerSec))
+		require.NoError(t, err)
+		if n == 0 {
+			break
+		}
+		time.Sleep(1 * time.Second)
+	}
+
+	// we should have 5 seconds of PCM data
+	require.Equal(t, 5*bytesPerSec, buf.Len())
+}