Write the test case for useEffect with Fetch API and useState in react

2 years ago

#56350

Krushna Kumar

Following are my code which includes the fetch API(getData) call with the useEffect and once get the response it will set the result into the setData using useState

I am trying to write the test case for the useEffect and useState but its failing and when I am seeing into the coverage ,I am getting the red background color with statements not covered for the useEffect block.

import { getData } from '../../api/data';

const [data, setData] = useState({});

  useEffect(() => {
    getData({ tableName }).then((response) => {
      try {
        if (response && response.result) {
          const result = Array.isArray(response.result)
            ? response.result[0]
            : response.result;
          const createDate = result.createdDate;
          result.name = result.firstName;
          result.submittedDate = `${createDate}`;
          result.attribute = Array.isArray(result.attribute)
            ? result.attribute
            : JSON.parse(result.attribute);
          setData(result);
        }
      } catch (error) {
        const errorObj = { error: error.message || 'error' };
        setData({ errorObj });
      }
    });
  }, []);

And I tried to write the test cases as following for the above code.

import React from "react";
import {
  shallowWithIntl,
  loadTranslation,
} from "../../../node_modules/enzyme-react-intl/lib/enzyme-react-intl";

import ParentPage from "ParentPage";
import ChildPage from "ChildPage";
import mockResponse from "mockData";
import { shallow, mount } from "enzyme";
import { act } from "react-dom/test-utils";


global.fetch = jest.fn(() =>
  Promise.resolve({
    json: () => Promise.resolve(mockResponse),
  })
);

describe("ParentPage", () => {
  let useEffect;
  let wrapper;
  const mockUseEffect = () => {
    useEffect.mockImplementationOnce((f) => f());
  };

  beforeEach(() => {
    const defaultProps = {
      tableName: "tableName",
    };

    wrapper = shallowWithIntl(<ParentPage {...defaultProps} />);
    useEffect = jest.spyOn(React, "useEffect");
    mockUseEffect();
  });

  it("Should render", () => {
    expect(wrapper).toMatchSnapshot();
  });
  it("Compenent render", async () => {
    let wrapper;
    await act(async () => {
      const setWidgets = jest.fn();
      const useStateSpy = jest.spyOn(React, "useState");
      useStateSpy.mockImplementation([mockResponse, setWidgets]);
      wrapper = await mount(<ChildPage data={mockResponse} />);
     
      await act(async () => {
        wrapper.update();
      });
      console.log(wrapper);
    });
  });
});

But when I tried using npm run test,And check the coverage I am still getting the statements not covered for the useEffect and useState.

What should I do to achieve the coverage as maximum as possible?

reactjs

enzyme

react-dom

jest-fetch-mock

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