Add test for rules typing

tests/orchestration/test_rules.py

@@ -0,0 +1,59 @@
+import pytest
+from langchain_openai import AzureChatOpenAI, ChatOpenAI
+from pydantic import BaseModel
+
+from controlflow.llm.rules import OpenAIRules
+
+
+class OpenAIFirst(BaseModel):
+    model: ChatOpenAI | AzureChatOpenAI
+
+
+class AzureFirst(BaseModel):
+    model: AzureChatOpenAI | ChatOpenAI
+
+
+class TestModelTypeValidation:
+    """
+    These tests document a bug in langchain's pydantic implementation where Union type
+    validation depends on the order of types. This is tested as a canary since the
+    behavior shouldn't affect controlflow - this test suite exists for reference only.
+    """
+
+    def test_openai_first_validation(self):
+        """Test validation when ChatOpenAI is first in Union"""
+        openai = ChatOpenAI(model="gpt-4")
+        azure = AzureChatOpenAI(api_version="1", azure_endpoint="2")
+
+        # OpenAI model should work
+        model = OpenAIFirst(model=openai)
+        assert isinstance(model.model, ChatOpenAI)
+
+        # Azure model should fail
+        with pytest.raises(Exception):
+            OpenAIFirst(model=azure)
+
+    def test_azure_first_validation(self):
+        """Test validation when AzureChatOpenAI is first in Union"""
+        openai = ChatOpenAI(model="gpt-4")
+        azure = AzureChatOpenAI(api_version="1", azure_endpoint="2")
+
+        # Azure model should work
+        model = AzureFirst(model=azure)
+        assert isinstance(model.model, AzureChatOpenAI)
+
+        # OpenAI model should fail
+        with pytest.raises(Exception):
+            AzureFirst(model=openai)
+
+    def test_controlflow_model_validation(self):
+        """Test that controlflow's own typing accepts both model types"""
+        openai = ChatOpenAI(model="gpt-4")
+        azure = AzureChatOpenAI(api_version="1", azure_endpoint="2")
+
+        # Both model types should work with OpenAIRules
+        rules_openai = OpenAIRules(model=openai)
+        assert isinstance(rules_openai.model, ChatOpenAI)
+
+        rules_azure = OpenAIRules(model=azure)
+        assert isinstance(rules_azure.model, AzureChatOpenAI)