[janmejai2002]

Summary

This PR adds unit test coverage for two subtle behavioral contracts in marshmallow.fields:

1. Field.make_error(**kwargs) formatting interpolation:

   • Field.make_error is designed to format error message templates with keyword arguments via msg.format(**kwargs).
   • Existing unit tests in tests/test_fields.py only exercised field.make_error(key) with static strings and without kwargs, leaving template parameter substitution unasserted.
   • Adds test_make_error_with_formatting_kwargs to verify that passing keyword arguments (e.g. field.make_error("formatted", field_name="age", min_val=18)) properly interpolates placeholders into the resulting ValidationError message.

2. Tuple partial valid_data retention on deserialization failure:

   • When a Tuple field encounters deserialization failures in one or more elements, it collects validly parsed elements into ValidationError.valid_data (raise ValidationError(errors, valid_data=result)).
   • Existing tests in tests/test_deserialization.py verified the error dictionary (exc.messages), but did not assert exc.valid_data.
   • Adds assertions verifying that:
     • Leading valid elements followed by invalid elements correctly populate exc.valid_data == ["good"].
     • Leading invalid elements followed by valid elements correctly populate exc.valid_data == ["good"] without inserting premature None entries.

---

Verification

• Tests: Ran pytest tests/test_fields.py tests/test_deserialization.py -q: 507 passed in 0.85s (0 failures).
• Linter: Ran ruff check and ruff format --check: all checks passed, 0 errors.
• Mocks: 0 synthetic mocks; tests use native fields.Tuple, fields.Integer, fields.Str, and real ValidationError instances.

[lafrech]

Not sure the latter is intended (#201340).