yaml Error while parsing. Expected <block end>, but found <scalar>

Question

I'm trying to test a swagger api with got-swag (npm package)

When I try to validate the json response with a json schema I get a parseError when the seperate yaml files get combined into one yaml and json file. The origin is the -validate() line. The validate() originates from the got-swag package but it fails in it's underlying jsonschema.validate( data, schema ); dependency

 x-tests:
        - description: Should return array of ferries
          steps:
            - get('/api/get/link/ferries')
            - equal(res.statusCode, 200)
            - ok(res.json.length > 0)
            - validate(res.json,  $ref: '#/definitions/ferry')

This is the resulting error:

           throw new exports.ParserError('while parsing a block mapping', this.marks.slice(-1)[0], "expected <block end>, but found " + token.id, token.start_mark);
        ^
while parsing a block mapping
  on line 29, column 15
expected <block end>, but found <scalar>
  on line 29, column 76
    at ParserError.YAMLError [as constructor] (C:\Users\dvbets\Documents\Workspace\Repos\node_modules\yaml-js\lib\errors.js:70:46)
    at ParserError.MarkedYAMLError [as constructor] (C:\Users\dvbets\Documents\Workspace\Repos\node_modules\yaml-js\lib\errors.js:90:45)
    at new ParserError (C:\Users\dvbets\Documents\Workspace\Repos\node_modules\yaml-js\lib\parser.js:17:48)
    at Loader.__dirname.Parser.Parser.parse_block_mapping_key (C:\Users\dvbets\Documents\Workspace\Repos\node_modules\yaml-js\lib\parser.js:433:15)
    at Loader.__dirname.Parser.Parser.check_event (C:\Users\dvbets\Documents\Workspace\Repos\node_modules\yaml-js\lib\parser.js:61:48)
    at Loader.__dirname.Composer.Composer.compose_mapping_node (C:\Users\dvbets\Documents\Workspace\Repos\node_modules\yaml-js\lib\composer.js:248:20)
    at Loader.__dirname.Composer.Composer.compose_node (C:\Users\dvbets\Documents\Workspace\Repos\node_modules\yaml-js\lib\composer.js:160:21)
    at Loader.__dirname.Composer.Composer.compose_sequence_node (C:\Users\dvbets\Documents\Workspace\Repos\node_modules\yaml-js\lib\composer.js:216:30)
    at Loader.__dirname.Composer.Composer.compose_node (C:\Users\dvbets\Documents\Workspace\Repos\node_modules\yaml-js\lib\composer.js:158:21)
    at Loader.__dirname.Composer.Composer.compose_mapping_node (C:\Users\dvbets\Documents\Workspace\Repos\node_modules\yaml-js\lib\composer.js:250:27)

Solution

That line needs to be wrapped in quotes in order to escape the inner : character:

- "validate(res.json,  $ref: '#/definitions/ferry')"
                           ^

: is a special character in YAML, a separator for key: value pairs. Without escaping, that line is parsed as the key name validate(res.json, $ref with the value '#/definitions/ferry') and the parser chokes on ) after the ending quotation mark.

Related: How to escape indicator characters (i.e. : or - ) in YAML