code: function assertRange(name, val, max) {
      assert.equal(typeof val, 'number', name + ' must be a number')
      assert(!isNaN(val), 'number', name + ' must be a number')
  
      if (val > max)
          throw new RangeError(name + ' must be lower than ' + max + ', but is ' + val)
      else if (val < 0)
          throw new RangeError(name + ' must be greater than or equal to zero, but is ' + val)
      else if (val % 1)
          throw new RangeError(name + ' must be an integer')
  }
docs: Assert a configurable value.
  
  @param {string} name
  @param {number} val
  @param {number} max