How to avoid type errors on mocked functions with TypeScript and Jest?

To avoid type errors on mocked functions with TypeScript and Jest, we use the typeof operator.

For instance, we write

import myModuleThatCallsAxios from "../myModule";
import axios from "axios";

jest.mock("axios");
const mockedAxios = axios as jest.Mocked<typeof axios>;

it("Calls the GET method as expected", async () => {
  const expectedResult: string = "result";

  mockedAxios.get.mockReturnValueOnce({ data: expectedResult });
  const result = await myModuleThatCallsAxios.makeGetRequest();

  expect(mockedAxios.get).toHaveBeenCalled();
  expect(result).toBe(expectedResult);
});

to cast the type of mockedAxios and axios to jest.Mocked<typeof axios>.

jest.Mocked is the generic type for mocked objects.

typeof axios gets the type of the axios object automatically.