tests.js

1. AppProvider.test.js

import React from "react";
import { render, unmountComponentAtNode } from "react-dom";
import { act } from "react-dom/test-utils";
import AppProvider from "./AppProvider";

describe("<AppProvider />", () => {
  let container = null;
  beforeEach(() => {
    container = document.createElement("div");
    document.body.appendChild(container);
  });
  afterEach(() => {
    unmountComponentAtNode(container);
    container.remove();
    container = null;
  });
  it("contains props children", async () => {
    await act(async () => {
      render(
        <AppProvider children={<p className="main">Hello World</p>} />,
        container
      );
    });
    expect(container.querySelector(".main").textContent).toBe("Hello World");
  });
});

2. App.test.js

import React from "react";
import { shallow } from "enzyme";
import App from "./App";

describe("<App/> ", () => {
  it("renders", () => {
    shallow(<App />);
  });
});