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

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

const { merge } = utils;

describe('utils::merge', function () {
  it('should be immutable', function () {
    const a = {};
    const b = { foo: 123 };
    const c = { bar: 456 };

    merge(a, b, c);

    expect(typeof a.foo).toEqual('undefined');
    expect(typeof a.bar).toEqual('undefined');
    expect(typeof b.bar).toEqual('undefined');
    expect(typeof c.foo).toEqual('undefined');
  });

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

    expect(d.foo).toEqual(789);
    expect(d.bar).toEqual(456);
  });

  it('should merge recursively', function () {
    const a = { foo: { bar: 123 } };
    const b = { foo: { baz: 456 }, bar: { qux: 789 } };

    expect(merge(a, b)).toEqual({
      foo: {
        bar: 123,
        baz: 456,
      },
      bar: {
        qux: 789,
      },
    });
  });

  it('should remove all references from nested objects', function () {
    const a = { foo: { bar: 123 } };
    const b = {};
    const d = merge(a, b);

    expect(d).toEqual({
      foo: {
        bar: 123,
      },
    });

    expect(d.foo).not.toBe(a.foo);
  });

  it('handles null and undefined arguments', function () {
    expect(merge(undefined, undefined)).toEqual({});
    expect(merge(undefined, { foo: 123 })).toEqual({ foo: 123 });
    expect(merge({ foo: 123 }, undefined)).toEqual({ foo: 123 });

    expect(merge(null, null)).toEqual({});
    expect(merge(null, { foo: 123 })).toEqual({ foo: 123 });
    expect(merge({ foo: 123 }, null)).toEqual({ foo: 123 });
  });

  it('should replace properties with null', function () {
    expect(merge({}, { a: null })).toEqual({ a: null });
    expect(merge({ a: null }, {})).toEqual({ a: null });
  });

  it('should replace properties with arrays', function () {
    expect(merge({}, { a: [1, 2, 3] })).toEqual({ a: [1, 2, 3] });
    expect(merge({ a: 2 }, { a: [1, 2, 3] })).toEqual({ a: [1, 2, 3] });
    expect(merge({ a: { b: 2 } }, { a: [1, 2, 3] })).toEqual({ a: [1, 2, 3] });
  });

  it('should replace properties with cloned arrays', function () {
    const a = [1, 2, 3];
    const d = merge({}, { a: a });

    expect(d).toEqual({ a: [1, 2, 3] });
    expect(d.a).not.toBe(a);
  });

  it('should support caseless option', () => {
    const a = { x: 1 };
    const b = { X: 2 };
    const merged = merge.call({ caseless: true }, a, b);

    expect(merged).toEqual({
      x: 2,
    });
  });
});