Function startFakeUpstream

nodejs/test/e2e/copilot_request_handler.e2e.test.ts:31–133

* Stand up an in-process upstream that speaks the real CAPI shapes the * runtime needs: model catalog, policy, `/responses` SSE for HTTP * inference, and a WebSocket endpoint at `/responses` that answers each * inbound `response.create` with the ordered `/responses` events the * reducer expects.

()

 * server directly; the handler does, on the runtime's behalf.
 */
async function startFakeUpstream(): Promise<{
    url: string;
    server: HttpServer;
    wsRequestCount: () => number;
    close: () => Promise<void>;
}> {
    let wsRequests = 0;

    const httpServer = createServer((req, res) => {
        const url = new URL(req.url ?? "/", `http://${req.headers.host ?? "localhost"}`);
        if (url.pathname === "/models" && req.method === "GET") {
            sendJson(res, 200, {
                data: [
                    {
                        id: "claude-sonnet-4.5",
                        name: "Claude Sonnet 4.5",
                        object: "model",
                        vendor: "Anthropic",
                        version: "1",
                        preview: false,
                        model_picker_enabled: true,
                        supported_endpoints: ["/responses", "ws:/responses"],
                        capabilities: {
                            type: "chat",
                            family: "claude-sonnet-4.5",
                            tokenizer: "o200k_base",
                            limits: {
                                max_context_window_tokens: 200000,
                                max_output_tokens: 8192,
                            },
                            supports: {
                                streaming: true,
                                tool_calls: true,
                                parallel_tool_calls: true,
                                vision: true,
                            },
                        },
                    },
                ],
            });
            return;
        }
        if (url.pathname.endsWith("/models/session")) {
            sendJson(res, 200, {});
            return;
        }
        if (url.pathname.includes("/policy")) {
            sendJson(res, 200, { state: "enabled" });
            return;
        }
        if (url.pathname.endsWith("/responses") && req.method === "POST") {
            // Single-shot HTTP inference (e.g. title generation). SSE
            // events the `responses-client.ts` reducer accepts.
            drainBody(req)
                .then(() => {
                    res.writeHead(200, {
                        "content-type": "text/event-stream",
                        "cache-control": "no-cache",