Check json structure: expect json, {mustBe: yes, sub: {weNeedThis: yes, butNotThis: no}}

expect.coffee

exports.expect = expect = (json, pattern, throws = false, current = []) ->
  condition = false
  for own key, value of pattern
    at = current.concat [key]
    if typeof value is 'boolean'
      condition = if value is true then json[key]? else not json[key]?
      if not condition and throws
        throw (if value is true then 'expected' else 'unexpected') + ' ' + at.join(' ')
    else
      if json[key]?
        condition = expect json[key], value, throws, at
      else
        condition = false
        if throws
          throw 'expected ' + at.join(' ')
  return condition