test(transcribe): gateway client and iguana->berget chain (red)

Gateway: field is `file`, no Expect header, a computed Content-Length (not
chunked, not buffered -- a 90 min WAV is ~170 MB), verbose_json normalised
with the last segment clamped to the audio duration, errors independent of
the body, an empty transcript is a failure. Chain: ANY primary failure falls
back and the row records the fallback endpoint; a cancelled job never falls
back to the cloud.

Red: package transcribe does not exist.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

internal/adapters/transcribe/chain_test.go

@@ -0,0 +1,99 @@
+package transcribe_test
+
+import (
+	"context"
+	"errors"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"git.d-ma.be/mathias/tapir/internal/adapters/transcribe"
+	"git.d-ma.be/mathias/tapir/internal/domain"
+)
+
+type fakeBackend struct {
+	name  string
+	text  string
+	err   error
+	calls int
+}
+
+func (f *fakeBackend) Name() string { return f.name }
+func (f *fakeBackend) Transcribe(_ context.Context, _ string) (domain.Transcription, error) {
+	f.calls++
+	if f.err != nil {
+		return domain.Transcription{}, f.err
+	}
+	return domain.Transcription{Text: f.text, Endpoint: f.name}, nil
+}
+
+func TestChain_PrimarySuccessNeverTouchesTheFallback(t *testing.T) {
+	primary := &fakeBackend{name: "iguana/kb-whisper", text: "primary text"}
+	fallback := &fakeBackend{name: "berget/kb-whisper", text: "fallback text"}
+
+	got, err := transcribe.NewChain(primary, fallback).Transcribe(context.Background(), "/a.wav")
+
+	require.NoError(t, err)
+	assert.Equal(t, "primary text", got.Text)
+	assert.Equal(t, "iguana/kb-whisper", got.Endpoint)
+	assert.Zero(t, fallback.calls, "audio must not leave the homelab when the local endpoint worked")
+}
+
+func TestChain_AnyPrimaryFailureFallsBackAndRecordsTheFallbackEndpoint(t *testing.T) {
+	tests := []struct {
+		name string
+		err  error
+	}{
+		{"server error", &transcribe.StatusError{Code: 500}},
+		{"gateway timeout", &transcribe.StatusError{Code: 504}},
+		{"client error", &transcribe.StatusError{Code: 400}},
+		{"transport failure", errors.New("dial tcp: connection refused")},
+		{"empty transcript", transcribe.ErrEmptyTranscript},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			primary := &fakeBackend{name: "iguana/kb-whisper", err: tt.err}
+			fallback := &fakeBackend{name: "berget/kb-whisper", text: "fallback text"}
+
+			got, err := transcribe.NewChain(primary, fallback).Transcribe(context.Background(), "/a.wav")
+
+			require.NoError(t, err)
+			assert.Equal(t, "fallback text", got.Text)
+			assert.Equal(t, "berget/kb-whisper", got.Endpoint,
+				"the row must say berget served it: that means the audio left the homelab")
+		})
+	}
+}
+
+func TestChain_BothFailingReportsBothErrors(t *testing.T) {
+	primary := &fakeBackend{name: "iguana/kb-whisper", err: errors.New("iguana down")}
+	fallback := &fakeBackend{name: "berget/kb-whisper", err: errors.New("berget down")}
+
+	_, err := transcribe.NewChain(primary, fallback).Transcribe(context.Background(), "/a.wav")
+
+	require.Error(t, err)
+	assert.Contains(t, err.Error(), "iguana down")
+	assert.Contains(t, err.Error(), "berget down")
+}
+
+func TestChain_WithoutAFallbackAPrimaryFailureIsTheResult(t *testing.T) {
+	primary := &fakeBackend{name: "iguana/kb-whisper", err: errors.New("iguana down")}
+
+	_, err := transcribe.NewChain(primary, nil).Transcribe(context.Background(), "/a.wav")
+
+	require.Error(t, err)
+	assert.Contains(t, err.Error(), "iguana down")
+}
+
+func TestChain_ACancelledJobDoesNotFallBack(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+	primary := &fakeBackend{name: "iguana/kb-whisper", err: context.Canceled}
+	fallback := &fakeBackend{name: "berget/kb-whisper", text: "x"}
+
+	_, err := transcribe.NewChain(primary, fallback).Transcribe(ctx, "/a.wav")
+
+	assert.ErrorIs(t, err, context.Canceled)
+	assert.Zero(t, fallback.calls, "a cancelled job must not ship the audio to a cloud endpoint")
+}

internal/adapters/transcribe/gateway_test.go

@@ -0,0 +1,174 @@
+package transcribe_test
+
+import (
+	"bytes"
+	"context"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"git.d-ma.be/mathias/tapir/internal/adapters/transcribe"
+	"git.d-ma.be/mathias/tapir/internal/domain"
+)
+
+// The httptest server stands in for the LiteLLM gateway: it is the process
+// boundary, so a fake here is legitimate. The JSON it returns mirrors what the
+// real gateway returned for iguana/kb-whisper and berget/kb-whisper on 2026-10-01
+// (docs/research/audio-length-ceiling-2026-10-01.md). All text is synthetic.
+
+const verboseJSON = `{
+  "text": " God morgon allihopa.\n Vi går igenom läget.\n",
+  "language": "swedish",
+  "duration": 4.25,
+  "segments": [
+    {"id": 0, "start": 0.0, "end": 1.0, "text": " God morgon allihopa."},
+    {"id": 1, "start": 1.0, "end": 9.0, "text": " Vi går igenom läget."}
+  ]
+}`
+
+func wavFile(t *testing.T, content string) string {
+	t.Helper()
+	p := filepath.Join(t.TempDir(), "a.wav")
+	require.NoError(t, os.WriteFile(p, []byte(content), 0o600))
+	return p
+}
+
+type seen struct {
+	method, path, auth, expect, contentType string
+	contentLength                           int64
+	transferEncoding                        []string
+	fields                                  map[string]string
+	file                                    string
+	fileField                               string
+	bodyLen                                 int
+}
+
+// serve starts a gateway fake that records the request it received and replies
+// with status and body.
+func serve(t *testing.T, status int, reply string, got *seen) *httptest.Server {
+	t.Helper()
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if got != nil {
+			got.method, got.path = r.Method, r.URL.Path
+			got.auth = r.Header.Get("Authorization")
+			got.expect = r.Header.Get("Expect")
+			got.contentType = r.Header.Get("Content-Type")
+			got.contentLength = r.ContentLength
+			got.transferEncoding = r.TransferEncoding
+			raw, _ := io.ReadAll(r.Body)
+			got.bodyLen = len(raw)
+			r.Body = io.NopCloser(bytes.NewReader(raw))
+			require.NoError(t, r.ParseMultipartForm(32<<20))
+			got.fields = map[string]string{}
+			for k, v := range r.MultipartForm.Value {
+				got.fields[k] = v[0]
+			}
+			for field, fhs := range r.MultipartForm.File {
+				got.fileField = field
+				f, _ := fhs[0].Open()
+				b, _ := io.ReadAll(f)
+				got.file = string(b)
+			}
+		}
+		w.WriteHeader(status)
+		_, _ = io.WriteString(w, reply)
+	}))
+	t.Cleanup(srv.Close)
+	return srv
+}
+
+func TestGateway_SendsTheRequestTheGatewayExpects(t *testing.T) {
+	var got seen
+	srv := serve(t, 200, verboseJSON, &got)
+	g := transcribe.NewGateway(srv.URL+"/v1", "secret-key", "iguana/kb-whisper", srv.Client())
+
+	_, err := g.Transcribe(context.Background(), wavFile(t, "RIFF-synthetic-pcm"))
+
+	require.NoError(t, err)
+	assert.Equal(t, http.MethodPost, got.method)
+	assert.Equal(t, "/v1/audio/transcriptions", got.path)
+	assert.Equal(t, "Bearer secret-key", got.auth)
+	assert.Equal(t, "file", got.fileField, "the multipart field is `file`; `audio_file` is rejected as 'Invalid request'")
+	assert.Equal(t, "RIFF-synthetic-pcm", got.file)
+	assert.Equal(t, "iguana/kb-whisper", got.fields["model"])
+	assert.Equal(t, "verbose_json", got.fields["response_format"])
+	assert.Equal(t, "sv", got.fields["language"])
+	assert.Empty(t, got.expect, "no Expect: 100-continue: it trips the proxy for any body over 1 KB")
+}
+
+func TestGateway_SendsAKnownContentLengthNotChunked(t *testing.T) {
+	var got seen
+	srv := serve(t, 200, verboseJSON, &got)
+	g := transcribe.NewGateway(srv.URL+"/v1", "k", "m", srv.Client())
+
+	_, err := g.Transcribe(context.Background(), wavFile(t, "0123456789"))
+
+	require.NoError(t, err)
+	assert.Empty(t, got.transferEncoding, "a 90-minute WAV is ~170 MB: stream it with a computed length, not chunked and not buffered")
+	assert.Equal(t, int64(got.bodyLen), got.contentLength)
+}
+
+func TestGateway_NormalisesTheVerboseJSONResponse(t *testing.T) {
+	srv := serve(t, 200, verboseJSON, nil)
+	g := transcribe.NewGateway(srv.URL+"/v1", "k", "iguana/kb-whisper", srv.Client())
+
+	got, err := g.Transcribe(context.Background(), wavFile(t, "x"))
+
+	require.NoError(t, err)
+	assert.Equal(t, "God morgon allihopa.\n Vi går igenom läget.", got.Text)
+	assert.Equal(t, "iguana/kb-whisper", got.Endpoint, "the serving endpoint is part of the result")
+	assert.InDelta(t, 4.25, got.AudioSeconds, 1e-9)
+	assert.Equal(t, []domain.Segment{
+		{Start: 0, End: 1, Text: "God morgon allihopa."},
+		// The final segment ended at 9.0 s for 4.25 s of audio: whisper's last
+		// window can run past the end. Clamped to the audio duration.
+		{Start: 1, End: 4.25, Text: "Vi går igenom läget."},
+	}, got.Segments)
+}
+
+func TestGateway_ErrorsDoNotDependOnTheBody(t *testing.T) {
+	// {"error":"failed to process audio"} has had at least five distinct causes, so
+	// no code may branch on it. Two different bodies must be treated identically.
+	for _, reply := range []string{`{"error":"failed to process audio"}`, `{"error":"something else entirely"}`} {
+		srv := serve(t, 500, reply, nil)
+		g := transcribe.NewGateway(srv.URL+"/v1", "k", "m", srv.Client())
+
+		_, err := g.Transcribe(context.Background(), wavFile(t, "x"))
+
+		var se *transcribe.StatusError
+		require.ErrorAs(t, err, &se)
+		assert.Equal(t, 500, se.Code)
+	}
+}
+
+func TestGateway_AnEmptyTranscriptIsAFailureNotASuccess(t *testing.T) {
+	srv := serve(t, 200, `{"text":"  ","language":"swedish","duration":3,"segments":[]}`, nil)
+	g := transcribe.NewGateway(srv.URL+"/v1", "k", "m", srv.Client())
+
+	_, err := g.Transcribe(context.Background(), wavFile(t, "x"))
+
+	assert.ErrorIs(t, err, transcribe.ErrEmptyTranscript)
+}
+
+func TestGateway_MalformedJSONIsAnError(t *testing.T) {
+	srv := serve(t, 200, `not json`, nil)
+	g := transcribe.NewGateway(srv.URL+"/v1", "k", "m", srv.Client())
+
+	_, err := g.Transcribe(context.Background(), wavFile(t, "x"))
+
+	assert.Error(t, err)
+}
+
+func TestGateway_MissingAudioFileIsAnError(t *testing.T) {
+	g := transcribe.NewGateway("http://127.0.0.1:1/v1", "k", "m", http.DefaultClient)
+
+	_, err := g.Transcribe(context.Background(), filepath.Join(t.TempDir(), "nope.wav"))
+
+	assert.Error(t, err)
+}