Function start

packages/react-router-node/__tests__/stream-test.ts:59–64

(controller)

    let readable = new ReadableStream<Uint8Array>({
      start(controller) {
        for (let i = 0; i < numChunks; i++) {
          controller.enqueue(new Uint8Array(chunkSize));
        }
        controller.close();
      },
    });

    await writeReadableStreamToWritable(readable, writable);