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fix: produce valid audio chunks when transcribing files >25MB #51

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Merged
End2EndAI merged 1 commit into from
Apr 6, 2026
Merged

fix: produce valid audio chunks when transcribing files >25MB #51

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110 changes: 41 additions & 69 deletions __tests__/processing.transcribeRecording.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,7 @@
* - supabase.auth → authenticated session
* - fetch → fake Whisper endpoint returning "chunk-<N>"
* - expo-file-system/legacy → in-memory file store
* - audio-splitter → returns pre-built chunks (web blobs / native temp URIs)
* - react-native Platform → overridable per describe block
*/

Expand Down Expand Up @@ -33,39 +34,32 @@ jest.mock('expo-file-system/legacy', () => ({
copyAsync: jest.fn(),
}));

jest.mock('../services/audio-splitter', () => ({
splitAudioWeb: jest.fn(),
splitAudioNative: jest.fn(),
}));

// ─── Imports (after mocks) ────────────────────────────────────────────────────

import * as FileSystem from 'expo-file-system/legacy';
import { Platform } from 'react-native';
import { transcribeRecording } from '../services/processing';
import { splitAudioWeb, splitAudioNative } from '../services/audio-splitter';

// ─── Constants ────────────────────────────────────────────────────────────────

const MB = 1024 * 1024;
const CHUNK_BYTES = 24 * MB;

// ─── Helpers ─────────────────────────────────────────────────────────────────

/** Build a base64 string that represents `bytes` bytes of binary data. */
function makeBase64(bytes: number): string {
return 'A'.repeat(Math.ceil(bytes / 3) * 4);
}

// ─── In-memory file store ─────────────────────────────────────────────────────

const fileStore: Record<string, string> = {};
const deletedUris: string[] = [];

// ─── Global fetch mock ────────────────────────────────────────────────────────

let whisperCallCount = 0;
const mockFetch = jest.fn();
const deletedUris: string[] = [];

beforeEach(() => {
jest.clearAllMocks();
whisperCallCount = 0;
deletedUris.length = 0;
Object.keys(fileStore).forEach(k => delete fileStore[k]);

// Default: native
(Platform as any).OS = 'native';
Expand All @@ -81,17 +75,9 @@ beforeEach(() => {
});
global.fetch = mockFetch as any;

// FileSystem: in-memory file store
(FileSystem.writeAsStringAsync as jest.Mock).mockImplementation((uri: string, data: string) => {
fileStore[uri] = data;
return Promise.resolve();
});
(FileSystem.readAsStringAsync as jest.Mock).mockImplementation((uri: string) =>
Promise.resolve(fileStore[uri] ?? '')
);
// FileSystem: track deletions
(FileSystem.deleteAsync as jest.Mock).mockImplementation((uri: string) => {
deletedUris.push(uri);
delete fileStore[uri];
return Promise.resolve();
});
});
Expand All @@ -105,47 +91,47 @@ describe('transcribeRecording — small file (≤ 25 MB)', () => {
const result = await transcribeRecording('file://recording.m4a');

expect(mockFetch).toHaveBeenCalledTimes(1);
expect(result).toBe('chunk-1');
expect(result).toEqual({
transcription: 'chunk-1',
uncertainTerms: [],
});
});
});

describe('transcribeRecording — large file (> 25 MB, native)', () => {
// 50 MB → ceil(50/24) = 3 chunks (24 MB + 24 MB + 2 MB)
const FILE_SIZE = 50 * MB;
const EXPECTED_CHUNKS = Math.ceil(FILE_SIZE / CHUNK_BYTES); // 3
const EXPECTED_CHUNKS = 3;
const tempUris = ['cache://chunk-0.m4a', 'cache://chunk-1.m4a', 'cache://chunk-2.m4a'];

beforeEach(() => {
(FileSystem.getInfoAsync as jest.Mock).mockResolvedValue({ exists: true, size: FILE_SIZE });
fileStore['file://recording.m4a'] = makeBase64(FILE_SIZE);
(FileSystem.getInfoAsync as jest.Mock).mockResolvedValue({ exists: true, size: 50 * MB });
(splitAudioNative as jest.Mock).mockResolvedValue(tempUris);
});

it('splits into the correct number of chunks', async () => {
it('calls splitAudioNative and sends one request per chunk', async () => {
await transcribeRecording('file://recording.m4a');

expect(splitAudioNative).toHaveBeenCalledWith('file://recording.m4a');
expect(mockFetch).toHaveBeenCalledTimes(EXPECTED_CHUNKS);
});

it('concatenates chunk transcriptions in order with a space', async () => {
const result = await transcribeRecording('file://recording.m4a');

const expected = Array.from({ length: EXPECTED_CHUNKS }, (_, i) => `chunk-${i + 1}`).join(' ');
expect(result).toBe(expected);
expect(result).toEqual({
transcription: expected,
uncertainTerms: [],
});
});

it('writes one temp file per chunk then deletes all of them', async () => {
it('deletes all temp files after transcription', async () => {
await transcribeRecording('file://recording.m4a');

expect(FileSystem.writeAsStringAsync).toHaveBeenCalledTimes(EXPECTED_CHUNKS);
expect(FileSystem.deleteAsync).toHaveBeenCalledTimes(EXPECTED_CHUNKS);

const writtenUris = (FileSystem.writeAsStringAsync as jest.Mock).mock.calls.map(
(c: any[]) => c[0] as string
);
expect(deletedUris.sort()).toEqual(writtenUris.sort());
expect(deletedUris.sort()).toEqual(tempUris.sort());
});

it('deletes all temp files even when Whisper throws', async () => {
// Make the second Whisper call fail
let calls = 0;
mockFetch.mockImplementation(() => {
calls += 1;
Expand All @@ -155,47 +141,29 @@ describe('transcribeRecording — large file (> 25 MB, native)', () => {

await expect(transcribeRecording('file://recording.m4a')).rejects.toThrow();

// Cleanup must still have run for all written temp files
const writtenUris = (FileSystem.writeAsStringAsync as jest.Mock).mock.calls.map(
(c: any[]) => c[0] as string
);
expect(writtenUris.length).toBeGreaterThan(0);
expect(deletedUris.sort()).toEqual(writtenUris.sort());
});

it('each chunk is the correct base64 size', async () => {
await transcribeRecording('file://recording.m4a');

const charsPerChunk = (CHUNK_BYTES / 3) * 4;
const chunkSizes = (FileSystem.writeAsStringAsync as jest.Mock).mock.calls.map(
(c: any[]) => (c[1] as string).length
);

// All chunks except the last must be exactly charsPerChunk
chunkSizes.slice(0, -1).forEach(len => expect(len).toBe(charsPerChunk));
// Last chunk is smaller (the remainder)
expect(chunkSizes[chunkSizes.length - 1]).toBeLessThan(charsPerChunk);
// All chunks together re-assemble to the full file
const totalChars = chunkSizes.reduce((a, b) => a + b, 0);
expect(totalChars).toBe(makeBase64(FILE_SIZE).length);
// Cleanup must still have run for all temp files
expect(deletedUris.sort()).toEqual(tempUris.sort());
});
});

describe('transcribeRecording — large file (> 25 MB, web)', () => {
// 30 MB → ceil(30/24) = 2 chunks
const FILE_SIZE = 30 * MB;
const EXPECTED_CHUNKS = Math.ceil(FILE_SIZE / CHUNK_BYTES); // 2
const EXPECTED_CHUNKS = 2;
const fakeBlobs = [
new Blob(['chunk-a'], { type: 'audio/wav' }),
new Blob(['chunk-b'], { type: 'audio/wav' }),
];

beforeEach(() => {
(Platform as any).OS = 'web';
(splitAudioWeb as jest.Mock).mockResolvedValue(fakeBlobs);

const blob = new Blob(['x'.repeat(FILE_SIZE)], { type: 'audio/webm' });
const originalBlob = new Blob(['x'.repeat(30 * MB)], { type: 'audio/webm' });
let calls = 0;
mockFetch.mockImplementation(() => {
calls += 1;
if (calls === 1) {
// First call is fetch(localUri) to get the blob
return Promise.resolve({ blob: () => Promise.resolve(blob) });
return Promise.resolve({ blob: () => Promise.resolve(originalBlob) });
}
const idx = calls - 1; // Whisper call index
return Promise.resolve({
Expand All @@ -205,9 +173,10 @@ describe('transcribeRecording — large file (> 25 MB, web)', () => {
});
});

it('splits into the correct number of Whisper calls', async () => {
it('calls splitAudioWeb and sends one Whisper request per chunk', async () => {
await transcribeRecording('blob:recording');

expect(splitAudioWeb).toHaveBeenCalled();
// 1 (blob fetch) + EXPECTED_CHUNKS (Whisper)
expect(mockFetch).toHaveBeenCalledTimes(1 + EXPECTED_CHUNKS);
});
Expand All @@ -216,7 +185,10 @@ describe('transcribeRecording — large file (> 25 MB, web)', () => {
const result = await transcribeRecording('blob:recording');

const expected = Array.from({ length: EXPECTED_CHUNKS }, (_, i) => `chunk-${i + 1}`).join(' ');
expect(result).toBe(expected);
expect(result).toEqual({
transcription: expected,
uncertainTerms: [],
});
});

it('does not touch the native filesystem', async () => {
Expand Down
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