Required Body parameters are not validated for their existence if they are not defined by $ref.
Given the following swagger.yml file:

swagger: '2.0'
info:
  title: foobar
  version: 0.0.1
schemes:
  - https
  - http
produces:
  - application/json
paths:
  /foo:
    post:
      consumes:
        - application/json
      parameters:
        - in: body
          name: body
          required: true
          schema:
            type: object
            required:
              - foo
            properties:
              foo:
                type: string
              bar:
                type: string
      responses:
        default:
          description: response
          schema:
            type: object
            properties:
              foo:
                type: string

If I POST an empty String with Content-Type: application/json it correctly validates as "Got value '' of type string. Value must be of type(s): ('object',)".
But now when I POST an empty JSON object it will validate as true.
Validation works if I POST an Integer for the foo param: "Got value 1 of type integer. Value must be of type(s): ('string',)"

If one define the body schema via $ref in definitions everything works fine, missing parameters are validated.

For validation I am using a populated Flex Request and flex.core.validate_api_request.