module.exports = function (compose) {
  return function () {
    const inc = n => n + 1
    const dbl = n => n * 2

    it('composes right to left', function () {
      compose(inc, dbl, 20).should.equal(41)
      compose(dbl, inc, 20).should.equal(42)
    })
  }
}

module.exports = function (compose) {
  return function () {
    const inc = (n) => n + 1
    const dbl = (n) => n * 2

    it('composes right to left', function () {
      compose(inc, dbl, 20).should.equal(41)
      compose(dbl, inc, 20).should.equal(42)
    })
  }
}

Clean up code, add parens
Clean up code, add parens
