fix(pytest): fix failing unit test test_model_copy[Environment]

packages/testing/src/execution_testing/base_types/pydantic.py

@@ -31,8 +31,38 @@ class CopyValidateModel(EthereumTestBaseModel):
     def copy(self: Self, **kwargs: Any) -> Self:
         """
         Create a copy of the model with the updated fields that are validated.
+
+        This method preserves the actual field values (including those set via
+        default_factory) while maintaining the model_fields_set to track which
+        fields were explicitly set.
+
+        The implementation uses exclude_unset=True as a safe baseline, then
+        explicitly adds back fields that were set via default_factory but not
+        explicitly set by the user. This avoids conflicts with models that have
+        mutually exclusive fields (e.g., Transaction with secret_key vs signature).
         """
-        return self.__class__(**(self.model_dump(exclude_unset=True) | kwargs))
+        # Start with explicitly set fields (safe baseline)
+        dump_dict = self.model_dump(exclude_unset=True)
+
+        # For fields with default_factory, include them if they're not in model_fields_set
+        # This handles cases like Environment.gas_limit where the factory captures
+        # dynamic configuration that should be preserved in copies
+        for field_name, field_info in self.__class__.model_fields.items():
+            if (
+                field_name not in self.model_fields_set
+                and field_info.default_factory
+            ):
+                dump_dict[field_name] = getattr(self, field_name)
+
+        # Merge with the updates
+        dump_dict.update(kwargs)
+        # Create the new instance
+        new_instance = self.__class__(**dump_dict)
+        # Preserve the original model_fields_set, adding any new kwargs
+        new_instance.__pydantic_fields_set__ = (
+            self.model_fields_set | kwargs.keys()
+        )
+        return new_instance
 
 
 class CamelModel(CopyValidateModel):