BC for pydantic v1

README.md

@@ -84,4 +84,5 @@ You can customize name and location of the fixture, but you will need to include
 ```
 
 ## Upgrading from v1
-As `pytest-interface-tester` v2 is using `pydantic` v2 that introduces breaking changes to their API, you might need to adjust your tested charm to also support v2. See [migration guide](https://docs.pydantic.dev/latest/migration/) for more information.
+`pytest-interface-tester` supports both pydantic v1 and v2, but using v2 is recommended.
+You might need to adjust your tested charm to also support v2. See [migration guide](https://docs.pydantic.dev/latest/migration/) for more information.

interface_tester/interface_test.py

@@ -10,6 +10,7 @@
 from enum import Enum
 from typing import Any, Callable, List, Literal, Optional, Union
 
+import pydantic
 from ops.testing import CharmType
 from pydantic import ValidationError
 from scenario import Context, Event, Relation, State
@@ -28,6 +29,14 @@
 
 logger = logging.getLogger(__name__)
 
+_has_pydantic_v1 = pydantic.version.VERSION.split(".") <= ["2"]
+
+
+def _validate(model: pydantic.BaseModel, obj: dict):
+    if _has_pydantic_v1:
+        return model.validate(obj)
+    return model.model_validate(obj)
+
 
 class InvalidTestCase(RuntimeError):
     """Raised if a function decorated with interface_test_case is invalid."""
@@ -283,7 +292,8 @@ def assert_schema_valid(self, schema: Optional["DataBagSchema"] = None):
         errors = []
         for relation in self._relations:
             try:
-                databag_schema.model_validate(
+                _validate(
+                    databag_schema,
                     {
                         "unit": relation.local_unit_data,
                         "app": relation.local_app_data,
@@ -441,7 +451,7 @@ def _get_endpoint(supported_endpoints: dict, role: Role, interface_name: str):
         return endpoints_for_interface[0]
 
     def _generate_relations_state(
-        self, state_template: State, input_state: State, supported_endpoints, role: Role
+            self, state_template: State, input_state: State, supported_endpoints, role: Role
     ) -> List[Relation]:
         """Merge the relations from the input state and the state template into one.
 

tests/unit/test_collect_schemas.py

@@ -3,6 +3,7 @@
 
 import pytest
 
+from interface_tester.interface_test import _has_pydantic_v1
 from interface_tester.collector import (
     collect_tests,
     get_schema_from_module,
@@ -70,8 +71,13 @@ class RequirerSchema(DataBagSchema):
     )
 
     tests = collect_tests(root)
-    assert tests["mytestinterfacea"]["v0"]["requirer"]["schema"].model_fields["foo"].default == 1
-    assert tests["mytestinterfaceb"]["v0"]["requirer"]["schema"].model_fields["foo"].default == 2
+    if _has_pydantic_v1:
+        assert tests["mytestinterfacea"]["v0"]["requirer"]["schema"].__fields__["foo"].default == 1
+        assert tests["mytestinterfaceb"]["v0"]["requirer"]["schema"].__fields__["foo"].default == 2
+
+    else:
+        assert tests["mytestinterfacea"]["v0"]["requirer"]["schema"].model_fields["foo"].default == 1
+        assert tests["mytestinterfaceb"]["v0"]["requirer"]["schema"].model_fields["foo"].default == 2
 
 
 def test_collect_invalid_schemas(tmp_path):