Axios-mock-adapter

mock
  .onGet("/users")
  .replyOnce(200, users) // After the first request to /users, this handler is removed
  .onGet("/users")
  .replyOnce(500); // The second request to /users will have status code 500
// Any following request would return a 404 since there are
// no matching handlers left

import axios from "axios";
import MockAdapter from "axios-mock-adapter";

import { BASE_URL, fetchUsers } from "./utils";

describe("fetchUsers", () => {
  let mock;

  beforeAll(() => {
    mock = new MockAdapter(axios);
  });

  afterEach(() => {
    mock.reset();
  });

  describe("when API call is successful", () => {
    it("should return users list", async () => {
      // given
      const users = [
        { id: 1, name: "John" },
        { id: 2, name: "Andrew" },
      ];
      mock.onGet(`${BASE_URL}/users`).reply(200, users);

      // when
      const result = await fetchUsers();

      // then
      expect(mock.history.get[0].url).toEqual(`${BASE_URL}/users`);
      expect(result.data).toEqual(users);
    });
  });

  describe("when API call fails", () => {
    it("should return empty users list", async () => {
      // given
      mock.onGet(`${BASE_URL}/users`).networkErrorOnce();

      // when
      const result = await fetchUsers();

      // then
      expect(mock.history.get[0].url).toEqual(`${BASE_URL}/users`);
      expect(result).toEqual([]);
    });
  });
});