How to use side_effect from pytest framework with pydantic.ValidationError class? #6459
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Hi, I'm trying to test my model validation exceptions with pytest. validate_mock = mocker.patch(
"my_package.MyClass.model_validate_json",
side_effect=pydantic.ValidationError(...),
)
TypeError: constructor is not definedHow to face this issue? Would you have an idea? Best regards, |
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Replies: 4 comments 4 replies
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The ValidationError class in Pydantic does not have a constructor, so you can't use the side_effect property to pass it as an argument to the mock.patch() function. you can use the side_effect_functools.partial() function to create a partial function that takes the exception message as an argument. |
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I tried like this, but it doesn't work: /usr/lib/python3.9/unittest/mock.py:1096: in _mock_call
return self._execute_mock_call(*args, **kwargs)
def _execute_mock_call(self, /, *args, **kwargs):
# separate from _increment_mock_call so that awaited functions are
# executed separately from their call, also AsyncMock overrides this method
effect = self.side_effect
if effect is not None:
if _is_exception(effect):
raise effect
elif not _callable(effect):
result = next(effect)
if _is_exception(result):
raise result
else:
> result = effect(*args, **kwargs)
E TypeError: No constructor defined
/usr/lib/python3.9/unittest/mock.py:1157: TypeError |
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what if you create a custom validation error class called my_validation_error. The my_validation_error class takes a single positional argument, which is the error message. then use the wraps function to wrap the my_validation_error class and add a constructor that takes a single positional argument. Finally, use the mocker.patch() function to patch the model_validate_json method in the MyClass class. something like this: |
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Hi @gamaleonardo, maybe as a workaround you could use a function that throws the ValidationError as a validate_mock = mocker.patch(
"my_package.MyClass.model_validate_json",
side_effect=lambda _: MyClass.model_validate_json(<some json that will fail the validation and cause a ValidationError>),
) |
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You could use from unittest.mock import Mock
from pydantic import ValidationError
func = Mock()
func.side_effect = ValidationError.from_exception_data("Invalid data", line_errors=[])
func() |
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Looks like the |
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For pydantic 1.x you can just do |
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Thank you! This helps |
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You could use
ValidationError.from_exception_data()method.