I'm using Jest with the coverage option on and I'm getting:

--------------------------|----------|----------|----------|----------|----------------|

File                      |  % Stmts | % Branch |  % Funcs |  % Lines |Uncovered Lines |

--------------------------|----------|----------|----------|----------|----------------|

progress-bar.js           |      100 |       75 |      100 |      100 |             17 |

--------------------------|----------|----------|----------|----------|----------------|

So I have 17 uncovered lines, but I'm not sure how to cover them.

progress-bar.js

import ProgressBar from 'progress'

import isNumber from 'lodash/isNumber'

import config from '../../config/global'



function progressBar (total) {

  if (!isNumber(total)) throw new Error(`progressBar() 'total' arg is not a number.`)



  const barCfg = config.progressBar



  const tokens = `${barCfg.bar} ${barCfg.info}`



  const options = {

    width: barCfg.width,

    total: total || 1,

    complete: barCfg.complete,

    incomplete: barCfg.incomplete

  }



  const bar = new ProgressBar(tokens, options)



  bar.render()



  return bar

}



export default progressBar

progress-bar.test.js

import ProgressBar from 'progress'

import progressBar from './progress-bar'



describe('progressBar()', () => {

  test('returns instanceof ProgressBar', () => {

    const actual = progressBar(5) instanceof ProgressBar

    const expected = true

    expect(actual).toBe(expected)

  })



  test('throw error if arg total is not a number', () => {

    expect(() => { progressBar('moo') }).toThrow()

    expect(() => { progressBar(null) }).toThrow()

  })



  test('progress bar progress/ticking', () => {

    const bar = progressBar(5)

    expect(bar.total).toBe(5)

    expect(bar.curr).toBe(0)

    bar.tick()

    expect(bar.curr).toBe(1)

    bar.tick()

    expect(bar.curr).toBe(2)

    bar.tick()

    expect(bar.curr).toBe(3)

    bar.tick()

    expect(bar.curr).toBe(4)

    bar.tick()

    expect(bar.curr).toBe(5)

    expect(bar.complete).toBe(true)

  })

})

So I'm testing the argument and return values.

How do I fully test this function, including the 17 lines..?