I’m trying to temporarily mock node-fetch in an ESM module while still retraining the original implementation so I can access a real endpoint’s value. However, this errors with “Must use import to load ES Module.” I recognize jest support for ESM is still pending – is there any way to have this behavior in a combination of current Node, ES6, and Jest?
worker.ts (dependency):
export default async () => {
const response = await fetch("http://example2.org");
return await response.json()
}
main.test.ts:
import { jest } from "@jest/globals";
jest.mock("node-fetch", () => {
return Promise.resolve({
json: () => Promise.resolve({ myItem: "abc" }),
})
})
import doWork from './worker.js';
import mockedFetch from 'node-fetch';
const originalFetch = jest.requireActual('node-fetch') as any;
test("Ensure mock", async () => {
const result = await doWork();
expect(result.myItem).toStrictEqual("abc");
expect(mockedFetch).toBeCalledTimes(1);
const response = await originalFetch("http://www.example.org");
expect(response.status).toBe(200);
const result2 = await doWork();
expect(result2.myItem).toStrictEqual("abc");
expect(mockedFetch).toBeCalledTimes(2);
});