@applicaster/zapp-react-native-utils/reactUtils/__tests__/reactUtilsHelpers.test.js

Applicaster Zapp React Native utilities package

import * as React from "react";
import { render } from "@testing-library/react-native";

import {
  isClassComponent,
  attachMethodToPrototype,
  wrapInClass,
  addLifeCycleMethods,
  isNilOrEmpty,
} from "../helpers";

import {
  ClassComponent,
  existingMethod,
  ComponentWithLifeCycle,
  StatelessComponent,
  componentDidMount,
  COMPONENT_DID_MOUNT_METHOD,
} from "./fixtures";

describe("reactUtils helpers", () => {
  describe("isNilOrEmpty", () => {
    it("should return correct output", () => {
      expect(isNilOrEmpty).toBeDefined();
      expect(isNilOrEmpty(null)).toBeTruthy();
      expect(isNilOrEmpty(undefined)).toBeTruthy();
      expect(isNilOrEmpty("")).toBeTruthy();
      expect(isNilOrEmpty([])).toBeTruthy();
    });
  });

  describe("isClassComponent", () => {
    it("returns true if the component is a class component", () => {
      expect(isClassComponent(ClassComponent)).toBe(true);
    });

    it("returns false otherwise", () => {
      expect(isClassComponent(StatelessComponent)).toBe(false);
    });
  });

  describe("attachMethodToPrototype", () => {
    const initialWrapper = render(<ClassComponent />);

    expect(initialWrapper.toJSON()).not.toHaveProperty(
      COMPONENT_DID_MOUNT_METHOD
    );

    afterEach(() => {
      componentDidMount.mockClear();
    });

    it("attaches a lifecycle method to the component's prototype", () => {
      const NewComponent = attachMethodToPrototype(ClassComponent)(
        componentDidMount,
        COMPONENT_DID_MOUNT_METHOD
      );

      const wrapper = render(<NewComponent />);

      expect(wrapper.toJSON(wrapper)).toMatchSnapshot();
      expect(new NewComponent()).toHaveProperty(COMPONENT_DID_MOUNT_METHOD);
      expect(componentDidMount).toHaveBeenCalled();
    });

    it("preserves any existing lifecycle method", () => {
      const NewComponent = attachMethodToPrototype(ComponentWithLifeCycle)(
        componentDidMount,
        COMPONENT_DID_MOUNT_METHOD
      );

      expect(componentDidMount).not.toHaveBeenCalled();

      const wrapper = render(<NewComponent />);

      expect(wrapper.toJSON()).toMatchSnapshot();
      expect(componentDidMount).toHaveBeenCalled();
      expect(existingMethod).toHaveBeenCalled();
    });
  });

  describe("wrapInClass", () => {
    let NewComponent;
    let wrapper;

    beforeEach(() => {
      NewComponent = wrapInClass(StatelessComponent);
      wrapper = render(<NewComponent />);
    });

    it("wraps the stateless component in a class", () => {
      expect(isClassComponent(NewComponent)).toBe(true);
      expect(wrapper.toJSON()).toMatchSnapshot();
    });
  });

  describe("addLifeCycleMethods", () => {
    let NewComponent;
    let wrapper;

    beforeEach(() => {
      NewComponent = addLifeCycleMethods({ componentDidMount })(ClassComponent);
      wrapper = render(<NewComponent />);
    });

    afterEach(() => {
      componentDidMount.mockClear();
    });

    it("attaches the lifecycle method to the component", () => {
      expect(wrapper.toJSON()).toMatchSnapshot();
    });

    it("adds the lifecycle method to the component", () => {
      expect(componentDidMount).toHaveBeenCalled();
    });
  });
});