text: 'use strict';
  
  // We want to globally mock this but jest doesn't let us do that by default
  // for a file that already exists. So we have to explicitly mock it.
  jest.mock('ReactDOMFeatureFlags', () => {
    const flags = require.requireActual('ReactDOMFeatureFlags');
    return Object.assign({}, flags, {
      useFiber: !!process.env.REACT_JEST_USE_FIBER,
    });
  });
  jest.mock('ReactFeatureFlags', () => {
    const flags = require.requireActual('ReactFeatureFlags');
    return Object.assign({}, flags, {
      disableNewFiberFeatures: true,
    });
  });
  jest.mock('ReactNativeFeatureFlags', () => {
    const flags = require.requireActual('ReactNativeFeatureFlags');
    return Object.assign({}, flags, {
      useFiber: !!process.env.REACT_JEST_USE_FIBER,
    });
  });
  
  // Error logging varies between Fiber and Stack;
  // Rather than fork dozens of tests, mock the error-logging file by default.
  jest.mock('ReactFiberErrorLogger');
  