merge.test.ts

import { isObject, merge } from '../src/merge';

describe('isObject function', () => {
  it('should accept valid arguments', () => {
    expect(isObject({ abc: 123 })).toBeTruthy();
  });

  it('should accept extreme arguments', () => {
    expect(isObject({ abc: 123, i: { am: 'nested' } })).toBeTruthy();
  });

  it('should reject erroneous arguments', () => {
    expect(isObject(false)).toBeFalsy();
    expect(isObject(undefined)).toBeFalsy();
    expect(isObject('hello world')).toBeFalsy();
    expect(isObject([123, 456])).toBeFalsy();
  });
});

describe('merging util function', () => {
  it('should merge two objects', () => {
    const a = { hello: 'world' };
    const b = { abc: 123 };

    const merged = merge(a, [b]);

    expect(Object.keys(merged)).toHaveLength(2);

    expect(merged).toHaveProperty('hello');
    expect(merged.hello).toEqual('world');

    expect(merged).toHaveProperty('abc');
    expect(merged.abc).toEqual(123);
  });

  it('should merge objects with nested values', () => {
    const a = { abc: { hello: 'world' } };
    const b = { abc: { easy: { as: 123 } } };

    const merged = merge(a, [b]);

    expect(Object.keys(merged)).toHaveLength(1);

    expect(merged).toHaveProperty('abc');
    expect(merged.abc).toHaveProperty('easy');
    expect(merged.abc.easy).toHaveProperty('as');
    expect(merged.abc.easy.as).toEqual(123);
    expect(merged.abc).toHaveProperty('hello');
    expect(merged.abc.hello).toEqual('world');
  });

  it('should merge array values when options.mergeArray is true', () => {
    const a = { hello: ['world'] };
    const b = { hello: ['there'], general: ['kenobi'] };

    const merged = merge(a, [b], { mergeArray: true });

    expect(Object.keys(merged)).toHaveLength(2);

    expect(merged).toHaveProperty('hello');
    expect(merged.hello).toHaveLength(2);
    expect(merged.hello).toContain('world');
    expect(merged.hello).toContain('there');

    expect(merged).toHaveProperty('general');
    expect(merged.general).toHaveLength(1);
    expect(merged.general).toContain('kenobi');
  });

  it('should not merge non-object values', () => {
    const a = { hello: 'world' };
    const b = [123, 456];

    const merged = merge(a, [b]);

    expect(Object.keys(merged)).toHaveLength(1);

    expect(merged).toHaveProperty('hello');
    expect(merged.hello).toEqual('world');
  });

  it('should return the target object if no sources are provided', () => {
    const a = { hello: 'world' };
    const merged = merge(a, []);

    expect(Object.keys(merged)).toHaveLength(1);
    expect(merged).toHaveProperty('hello');
    expect(merged.hello).toEqual('world');
  });

  it('should ignore non-object sources', () => {
    const a = { hello: 'world' };
    const b = [123, 456];

    const merged = merge(a, b);

    expect(Object.keys(merged)).toHaveLength(1);
    expect(merged).toHaveProperty('hello');
    expect(merged.hello).toEqual('world');
  });
});