axios/test/specs/utils/extend.spec.js

import utils from '../../../lib/utils';

const { extend } = utils;

describe('utils::extend', function () {
  it('should be mutable', function () {
    const a = {};
    const b = { foo: 123 };

    extend(a, b);

    expect(a.foo).toEqual(b.foo);
  });

  it('should extend properties', function () {
    let a = { foo: 123, bar: 456 };
    const b = { bar: 789 };

    a = extend(a, b);

    expect(a.foo).toEqual(123);
    expect(a.bar).toEqual(789);
  });

  it('should bind to thisArg', function () {
    const a = {};
    const b = {
      getFoo: function getFoo() {
        return this.foo;
      },
    };
    const thisArg = { foo: 'barbaz' };

    extend(a, b, thisArg);

    expect(typeof a.getFoo).toEqual('function');
    expect(a.getFoo()).toEqual(thisArg.foo);
  });
});