message: Increase test code coverage for formatISO API
diff: /* eslint-env mocha */
  import assert from 'power-assert'
  +import sinon from 'sinon'
  import formatISO from '.'
  import addLeadingZeros from '../_lib/addLeadingZeros'
  @@ -31,6 +32,21 @@ describe('formatISO', () => {
  const date = new Date(2019, 2 /* Mar */, 3, 19, 0, 52, 123)
  const tzOffsetExtended = generateOffset(date)
  assert(formatISO(date) === `2019-03-03T19:00:52${tzOffsetExtended}`)
  +
  + const getTimezoneOffsetStub = sinon.stub(
  + Date.prototype,
  + 'getTimezoneOffset'
  + )
  +
  + getTimezoneOffsetStub.returns(480)
  + const tzNegativeOffsetExtended = generateOffset(date)
  + assert(formatISO(date) === `2019-03-03T19:00:52${tzNegativeOffsetExtended}`)
  +
  + getTimezoneOffsetStub.returns(0)
  + const tzZOffsetExtended = generateOffset(date)
  + assert(formatISO(date) === `2019-03-03T19:00:52${tzZOffsetExtended}`)
  +
  + getTimezoneOffsetStub.restore()
  })
  it('accepts a timestamp', () => {
  @@ -99,7 +115,7 @@ describe('formatISO', () => {
  it("throws `RangeError` if `options.format` is not 'extended' or 'basic'", function () {
  // $ExpectedMistake
  var block = formatISO.bind(null, new Date(2019, 2 /* Mar */, 3), {
  - format: 'something else'
  + format: 'something else',
  })
  assert.throws(block, RangeError)
  })
  @@ -107,7 +123,7 @@ describe('formatISO', () => {
  it("throws `RangeError` if `options.representation` is not 'date', 'time' or 'complete'", function () {
  // $ExpectedMistake
  var block = formatISO.bind(null, new Date(2019, 2 /* Mar */, 3), {
  - representation: 'something else'
  + representation: 'something else',
  })
  assert.throws(block, RangeError)
  })
  