---

description: Use hookFetch instead of assigning or spying on globalThis.fetch in tests condition: "globalThis\.fetch\s*=|spyOn\(globalThis.fetch" scope: "tool:edit(**/.test.{ts,tsx,js,jsx}), tool:write(**/*.test.{ts,tsx,js,jsx})"

Do not assign globalThis.fetch or use vi.spyOn(globalThis, "fetch") in tests.

Why it's wrong

• Forgetting restoration leaks state across tests
• vi.spyOn ties fetch mocking to vitest lifecycle instead of explicit scoping
• Makes test mocking inconsistent across the codebase

What to use instead

Use hookFetch from @oh-my-pi/pi-utils. It returns a Disposable — use using for automatic cleanup:

import { hookFetch } from "@oh-my-pi/pi-utils";

using _hook = hookFetch((input, init, next) => {
	// return a mocked Response, or delegate with next(input, init)
});

Examples

// WRONG
globalThis.fetch = async () => new Response("ok");

// WRONG
vi.spyOn(globalThis, "fetch").mockResolvedValue(new Response("ok"));

// RIGHT — fixed response
using _hook = hookFetch(() => new Response("ok"));

// RIGHT — conditional mock with passthrough
using _hook = hookFetch((input, init, next) => {
	if (String(input).includes("127.0.0.1")) {
		return new Response(JSON.stringify({ data: [] }));
	}
	return next(input, init);
});

// RIGHT — when you need vi.fn() for mock assertions
const fetchSpy = vi.fn(() => new Response("ok"));
using _hook = hookFetch(fetchSpy);
// later: expect(fetchSpy.mock.calls[0]).toEqual(...)