@mapbox/mr-ui/utils/use_previous.test.js

UI components for Mapbox projects

"use strict";

var _react = require("@testing-library/react");
var _use_previous = _interopRequireDefault(require("./use_previous"));
function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
const setUp = () => (0, _react.renderHook)(_ref => {
  let {
    state
  } = _ref;
  return (0, _use_previous.default)(state);
}, {
  initialProps: {
    state: 0
  }
});
describe('usePrevious', () => {
  test('should return undefined on initial render', () => {
    const {
      result
    } = setUp();
    expect(result.current).toBeUndefined();
  });
  test('should always return previous state after each update', () => {
    const {
      result,
      rerender
    } = setUp();
    rerender({
      state: 2
    });
    expect(result.current).toBe(0);
    rerender({
      state: 4
    });
    expect(result.current).toBe(2);
    rerender({
      state: 6
    });
    expect(result.current).toBe(4);
  });
});