js__react_enzyme__egghead/src/App.test.js

import "raf/polyfill";
import React from "react";
import { App, appName, Link, titleName } from "./App";
import { configure, shallow, mount } from "enzyme";
import Adapter from "enzyme-adapter-react-16";
import toJson from "enzyme-to-json";

// Configure Enzyme for the React version we are using.
// Could be in a test setup file. Required for React 16, 15, 0.14, 0.13.
configure({ adapter: new Adapter() });

describe("<App /> shallow rendering", () => {
  const wrapper = shallow(<App />);

  it("should find its elements", () => {
    // There is one <p> in <App />: only one shoud be present in shallow rendering.
    expect(wrapper.find("p").length).toBe(3);
    expect(wrapper.find("p.App-intro").exists()).toBe(true);
    expect(wrapper.find("ul").hasClass("tyler")).toBe(true);
    expect(wrapper.find("ul").children().length).toBe(3);
    expect(wrapper.find("h1").text()).toBe("Welcome to React");
  });

  it("should find using props", () => {
    // "key" and "ref" could not be used that way.

    // CSS attribute syntax.
    expect(wrapper.find("[text='Some title']").length).toBe(1);
    // Object property selector.
    expect(wrapper.find({ text: "Some title" }).length).toBe(1);
  });

  // FIXME cannot make sense of video.
  // @see http://airbnb.io/enzyme/docs/api/ReactWrapper/find.html
  test.skip("should find using a constructor", () => {
    // expect(wrapper.find(function App() { return ... }).length).toBe(1);
  });

  it("should find using displayName", () => {
    const w = mount(<App />);
    expect(w.find(appName).length).toBe(1);
    expect(w.find(titleName).length).toBe(1);
  });

  it("matches the snapshot", () => {
    const tree = shallow(<App />);
    expect(toJson(tree)).toMatchSnapshot();
  });

  it("should change p text on button click", () => {
    const button = wrapper.find("button");
    expect(wrapper.find(".button-state").text()).toBe("No!");

    // Simulate() will fetch the onClick prop  on the component and call it.
    button.simulate("click");
    expect(wrapper.find(".button-state").text()).toBe("Yes!");
  });

  it("should update className with new State", () => {
    expect(wrapper.find(".blue").length).toBe(1);
    expect(wrapper.find(".red").length).toBe(0);

    // Invoking setState() on the wrapper invokes in on the underlying component,
    // and causes a rerender.
    wrapper.setState({ mainColor: "red" });
    expect(wrapper.find(".blue").length).toBe(0);
    expect(wrapper.find(".red").length).toBe(1);
  });

  it("should change title text on input change", () => {
    const input = wrapper.find("input");
    const expected = "Tyler";

    expect(wrapper.find("h2").text()).toBe("");
    // The optional parameter is the mocked event.
    input.simulate("change", { currentTarget: { value: expected } });
    expect(wrapper.find("h2").text()).toBe(expected);
  });

  it("should call componentDidMount, update p tag text", () => {
    jest.spyOn(App.prototype, "componentDidMount");
    const w = shallow(<App />);

    // Needs the method to be defined on the component for it to be invoked.
    expect(App.prototype.componentDidMount.mock.calls.length).toBe(1);
    expect(w.find(".lifeCycle").text()).toBe("componentDidMount");
  });

  it("should call componentWillReceiveProps", () => {
    jest.spyOn(App.prototype, "componentWillReceiveProps");
    const w = shallow(<App />);

    expect(w.find(".lifeCycle").text()).toBe("componentDidMount");

    // Needs the method to be defined on the component for it to be invoked.
    expect(App.prototype.componentWillReceiveProps.mock.calls.length).toBe(0);

    w.setProps({ hide: true });
    expect(App.prototype.componentWillReceiveProps.mock.calls.length).toBe(1);
    expect(w.find(".lifeCycle").text()).toBe("componentWillReceiveProps");
  });

  it("should return correctly from handleStrings()", () => {
    // instance() provides access to the underlying class implementing the component.
    const expectations = {
      "Hello, world": true,
      "": false,
    };

    for (const [value, expected] of Object.entries(expectations)) {
      const actual = wrapper.instance().handleStrings(value);
      expect(actual).toBe(expected);
    }
  });
});

describe("<App /> mount rendering", () => {
  it("h1 contains correct text", () => {
    // Second parameter is optional.
    const wrapper = mount(<App />, {
      context: {},
      attachTo: document.createElement("div"),
    });

    expect(wrapper.find("h1").text()).toBe("Welcome to React");
    // Tests can affect each other if mounted components are not unmounted,
    // since they will remain mounted in the same DOM.
    // Unmount() can also be used to simulate an unmount/mount cycle in React.
    wrapper.unmount();
  });

  it("matches the snapshot", () => {
    const tree = mount(<App />);
    expect(toJson(tree)).toMatchSnapshot();
    tree.unmount();
  });
});

describe("<Link>", () => {
  const expected = "www.google.com";

  it("link component accepts address prop", () => {
    const wrapper = shallow(<Link address={expected} />);
    // wrapper.instance() is the React component. "props" is a property.
    expect(wrapper.instance().props.address).toBe(expected);
  });

  // wrapper itself is the ShallowWrapper instance, not the React component.
  it("tag node renders href correctly", () => {
    const wrapper = shallow(<Link address={expected} />);
    // Check its rendering:
    // console.log(wrapper.html(), wrapper.props());
    expect(wrapper.prop("href")).toBe(expected);
    // Here "props" is a method, not a property.
    expect(wrapper.props().href).toBe(expected);
  });

  it("returns null with true hide prop", () => {
    const wrapper = shallow(<Link address={expected} hide={false} />);
    expect(wrapper.find("a").length).toBe(1);
    expect(wrapper.props().href).toBe(expected);

    // Causes a rerender() of the component.
    // - triggers componentWillReceiveProps()
    wrapper.setProps({ hide: true });

    expect(wrapper.find("a").length).toBe(0);
    // Dangerous: some versions of React might inject comments in HTML.
    // expect(wrapper.html()).toBeNull();

    // expect(wrapper.getNode()).toBeNull();
    // Obsolete: getNode() is deprecated.

    // Recommended way https://github.com/airbnb/enzyme/issues/52
    expect(wrapper.getElement()).toBe(null);
    expect(wrapper.getElement()).toBeNull();
    // Get() returns the node at the given index on the wrapper.
    expect(wrapper.get(0)).toBeNull();
  });
});