How to use the prance.BaseParser function in prance

def test_flex_validate_failure():
  with pytest.raises(ValidationError):
    parser = BaseParser('tests/specs/missing_reference.yaml', backend = 'flex')

def test_openapi_spec_validator_validate_failure():
  with pytest.raises(ValidationError):
    parser = BaseParser('tests/specs/missing_reference.yaml', backend = 'openapi-spec-validator')

def test_convert_spec():
  from prance import BaseParser, ResolvingParser, ValidationError
  parser = BaseParser('tests/specs/petstore.yaml')

  # Conversion should fail with the default backend.
  with pytest.raises(ValidationError):
    converted = convert.convert_spec(parser.specification)

  # However, with the lazy flag it should work.
  converted = convert.convert_spec(parser.specification, lazy = True)
  assert isinstance(converted, BaseParser)

  # Passing a ResolvingParser class should also work.
  converted = convert.convert_spec(parser.specification, ResolvingParser, lazy = True)
  assert isinstance(converted, ResolvingParser)

def test_flex_issue_5_integer_keys():
  # Must succeed with default (flex) parser; note the parser does not stringify the response code
  parser = BaseParser('tests/specs/issue_5.yaml', backend = 'flex')
  assert 200 in parser.specification['paths']['/test']['post']['responses']

def test_swagger_spec_validator_validate_failure():
  with pytest.raises(ValidationError):
    parser = BaseParser('tests/specs/missing_reference.yaml', backend = 'swagger-spec-validator')

def test_openapi_spec_validator_issue_20_spec_version_handling():
  # The spec is OpenAPI 3, but broken. Need to set 'strict' to False to stringify keys
  with pytest.raises(ValidationError):
    parser = BaseParser('tests/specs/issue_20.yaml', backend = 'openapi-spec-validator', strict = False)

  # Lazy parsing should let us validate what's happening
  parser = BaseParser('tests/specs/issue_20.yaml', backend = 'openapi-spec-validator', strict = False, lazy = True)
  assert not parser.valid
  assert parser.version_parsed == ()

  with pytest.raises(ValidationError):
    parser.parse()

  # After parsing, the specs are not valid, but the correct version is
  # detected.
  assert not parser.valid
  assert parser.version_parsed == (3, 0, 0)

def test_swagger_spec_validator_issue_5_integer_keys():
  # Must fail in implicit strict mode.
  with pytest.raises(ValidationError):
    BaseParser('tests/specs/issue_5.yaml', backend = 'swagger-spec-validator')

  # Must fail in explicit strict mode.
  with pytest.raises(ValidationError):
    BaseParser('tests/specs/issue_5.yaml', backend = 'swagger-spec-validator', strict = True)

  # Must succeed in non-strict/lenient mode
  parser = BaseParser('tests/specs/issue_5.yaml', backend = 'swagger-spec-validator', strict = False)
  assert '200' in parser.specification['paths']['/test']['post']['responses']

def test_convert_parser_lazy_swagger_backend():
  from prance import BaseParser, ResolvingParser, ValidationError
  parser = BaseParser('tests/specs/petstore.yaml')

  # Conversion should fail with the default backend.
  with pytest.raises(ValidationError):
    converted = convert.convert_spec(parser)

  # However, with the lazy flag it should work.
  converted = convert.convert_spec(parser, lazy = True)
  assert isinstance(converted, BaseParser)

  # Passing a ResolvingParser class should also work.
  converted = convert.convert_spec(parser, ResolvingParser, lazy = True)
  assert isinstance(converted, ResolvingParser)

:raise: apispec.exceptions.OpenAPIError if validation fails.
    """
    try:
        import prance
    except ImportError as error:  # re-raise with a more verbose message
        exc_class = type(error)
        raise exc_class(
            "validate_spec requires prance to be installed. "
            "You can install all validation requirements using:\n"
            "    pip install 'apispec[validation]'"
        )
    parser_kwargs = {}
    if spec.openapi_version.version[0] == 3:
        parser_kwargs["backend"] = "openapi-spec-validator"
    try:
        prance.BaseParser(spec_string=json.dumps(spec.to_dict()), **parser_kwargs)
    except prance.ValidationError as err:
        raise exceptions.OpenAPIError(*err.args)
    else:
        return True