o/src/__tests__/map.spec.ts

common object helper functions

import map from '../map'
import { OObject, MapCallback } from '../types'

describe('map', (): void => {
  test('should run the callback on all keys in the object', (): void => {
    const obj = {
      a: 1,
      b: 2
    }
    const cb = jest.fn()

    map(obj, cb)

    expect(cb.mock.calls).toHaveLength(2)
  })

  test('should return a new object not a reference', (): void => {
    const obj = {
      a: 1,
      b: 2
    }

    const result = map(obj, jest.fn())
    result.a = 5

    expect(typeof result).toBe('object')
    expect(obj.a).toBe(1)
  })

  test('returned object values should be computed using the callback', (): void => {
    const obj = {
      a: 1,
      b: 2,
      c: 3
    }

    const result = map(obj, (k, v): number => v * 2)

    expect(result.a).toBe(2)
    expect(result.b).toBe(4)
    expect(result.c).toBe(6)
  })

  test('should compute deep object values when follow is true', (): void => {
    const obj = {
      a: 1,
      b: {
        c: 2,
        d: 3
      }
    }

    const resultA = map(obj, (k, v): number => v * 2, {
      follow: false
    })
    const resultB = map(obj, (k, v): number => v * 2, {
      follow: true
    })

    expect(resultA.a).toBe(2)
    expect(resultA.b).toBe(NaN)
    expect(resultB.a).toBe(2)
    expect(typeof resultB.b).toBe('object')
    expect(resultB.b.c).toBe(4)
    expect(resultB.b.d).toBe(6)
  })

  test('should throw TypeError for invalid arguments', (): void => {
    const invalidObj: unknown = 'testing'
    const invalidCallback: unknown = 'testing'
    const invalidFollow: unknown = 'testing'

    expect((): OObject => map(invalidObj as OObject, jest.fn()))
      .toThrow(new TypeError('Expected Object, got string testing'))
    expect((): OObject => map({}, invalidCallback as MapCallback))
      .toThrow(new TypeError('Expected Function, got string testing'))
    expect((): OObject => map({}, jest.fn(), {
      follow: invalidFollow as boolean
    }))
      .toThrow(new TypeError('Expected Boolean, got string testing'))
  })
})