babel-preset-test-bundled-dependencies/node_modules/core-js/modules/_an-instance.js

Allow custom config for create-react-app without ejecting

module.exports = function(it, Constructor, name, forbiddenField){
  if(!(it instanceof Constructor) || (forbiddenField !== undefined && forbiddenField in it)){
    throw TypeError(name + ': incorrect invocation!');
  } return it;
};