Restore unit test that consider minLength, maxLength and pattern in referenced schema

[jmini]

This PR restores the unit test that consider minLength, maxLength and pattern when they are defined in a in referenced schema.

OAS2 example:

definitions:
  SomeObj:
    type: object
    properties:
      nick:
        $ref: "#/definitions/NickName"
  NickName:
    type: string
    minLength: 1
    maxLength: 3
    pattern: "^[A-Z]+$"

This was filed as originally as swagger-api/swagger-codegen#8001

I have tried to implement a solution for this with #45, but my solution had too many side effects and was reverted with #82.

This PR brings back the tests without changing anything to the implementation. I think the changes made with #360 by @wing328 solves also issue swagger-api/swagger-codegen#8001.

[jmini]

Unit tests are green, this PR is just about new assertions in one unit test, no changes to the implementation. => Self approving.