Validation result object

Build a class that collects validation errors and reports whether the input is valid.

validation error-handling oop classes

Implement a class `ValidationResult` that collects validation error messages and reports whether validation passed. The class must have:
- `__init__(self)`: initializes an empty collection of error messages.
- `add_error(self, message: str) -> None`: appends `message` to the collection.
- `is_valid(self) -> bool`: returns `True` if there are no errors, `False` otherwise.
- `errors(self) -> list[str]`: returns a NEW list containing the error messages in the order they were added. The returned list must be a copy, not a reference to the internal state.

Use these methods to accumulate errors and then check validity.

Constraints

No external packages. The number of errors is unlimited. Error messages are non-empty strings. The returned list from `errors()` must be independent of internal state.

Example

>>> result = ValidationResult()
>>> result.is_valid()
True
>>> result.add_error('name is required')
>>> result.add_error('email is invalid')
>>> result.is_valid()
False
>>> result.errors()
['name is required', 'email is invalid']

8 points ~15 min

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Hints

Store error messages in a list attribute inside __init__.

add_error should append the message to that list.

is_valid should check whether the list is empty.

errors should return a copy (e.g., list(self._errors)) so external mutations don't affect internal state.

Test Results

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