Increased test coverage for ChatAdapter (#8168)

* test(ChatAdapter): Increased test coverage for ChatAdapter

* test(ChatAdapter): Modified input for pydantic test

* test(ChatAdapter): Slight change to exception test

* test(ChatAdapter): Modified pydantic test case to a more user-friendly format

* test(ChatAdapter): removed some unneeded print statements

* test(ChatAdapter): Added descriptive comments

* fix test

---------

Co-authored-by: chenmoneygithub <chen.qian@databricks.com>

Author: JHMuir

tests/adapters/test_chat_adapter.py

@@ -1,6 +1,7 @@
 from typing import Literal
 from unittest import mock
 
+import pydantic
 import pytest
 
 import dspy
@@ -97,6 +98,106 @@ async def test_chat_adapter_async_call():
     assert result == [{"answer": "Paris"}]
 
 
+def test_chat_adapter_with_pydantic_models():
+    """
+    This test verifies that ChatAdapter can handle different input and output field types, both basic and nested.
+    """
+
+    class DogClass(pydantic.BaseModel):
+        dog_breeds: list[str] = pydantic.Field(description="List of the breeds of dogs")
+        num_dogs: int = pydantic.Field(description="Number of dogs the owner has", ge=0, le=10)
+
+    class PetOwner(pydantic.BaseModel):
+        name: str = pydantic.Field(description="Name of the owner")
+        num_pets: int = pydantic.Field(description="Amount of pets the owner has", ge=0, le=100)
+        dogs: DogClass = pydantic.Field(description="Nested Pydantic class with dog specific information ")
+
+    class Answer(pydantic.BaseModel):
+        result: str
+        analysis: str
+
+    class TestSignature(dspy.Signature):
+        owner: PetOwner = dspy.InputField()
+        question: str = dspy.InputField()
+        output: Answer = dspy.OutputField()
+
+    dspy.configure(lm=dspy.LM(model="openai/gpt4o"), adapter=dspy.ChatAdapter())
+    program = dspy.Predict(TestSignature)
+
+    with mock.patch("litellm.completion") as mock_completion:
+        program(
+            owner=PetOwner(name="John", num_pets=5, dogs=DogClass(dog_breeds=["labrador", "chihuahua"], num_dogs=2)),
+            question="How many non-dog pets does John have?",
+        )
+
+    mock_completion.assert_called_once()
+    _, call_kwargs = mock_completion.call_args
+
+    system_content = call_kwargs["messages"][0]["content"]
+    user_content = call_kwargs["messages"][1]["content"]
+    assert "1. `owner` (PetOwner)" in system_content
+    assert "2. `question` (str)" in system_content
+    assert "1. `output` (Answer)" in system_content
+
+    assert "name" in user_content
+    assert "num_pets" in user_content
+    assert "dogs" in user_content
+    assert "dog_breeds" in user_content
+    assert "num_dogs" in user_content
+    assert "How many non-dog pets does John have?" in user_content
+
+
+def test_chat_adapter_signature_information():
+    """
+    This test ensures that the signature information sent to the LM follows an expected format.
+    """
+
+    class TestSignature(dspy.Signature):
+        input1: str = dspy.InputField(desc="String Input")
+        input2: int = dspy.InputField(desc="Integer Input")
+        output: str = dspy.OutputField(desc="String Output")
+
+    dspy.configure(lm=dspy.LM(model="openai/gpt4o"), adapter=dspy.ChatAdapter())
+    program = dspy.Predict(TestSignature)
+
+    with mock.patch("litellm.completion") as mock_completion:
+        program(input1="Test", input2=11)
+
+    mock_completion.assert_called_once()
+    _, call_kwargs = mock_completion.call_args
+
+    assert len(call_kwargs["messages"]) == 2
+    assert call_kwargs["messages"][0]["role"] == "system"
+    assert call_kwargs["messages"][1]["role"] == "user"
+
+    system_content = call_kwargs["messages"][0]["content"]
+    user_content = call_kwargs["messages"][1]["content"]
+
+    assert "1. `input1` (str)" in system_content
+    assert "2. `input2` (int)" in system_content
+    assert "1. `output` (str)" in system_content
+    assert "[[ ## input1 ## ]]\n{input1}" in system_content
+    assert "[[ ## input2 ## ]]\n{input2}" in system_content
+    assert "[[ ## output ## ]]\n{output}" in system_content
+    assert "[[ ## completed ## ]]" in system_content
+
+    assert "[[ ## input1 ## ]]" in user_content
+    assert "[[ ## input2 ## ]]" in user_content
+    assert "[[ ## output ## ]]" in user_content
+    assert "[[ ## completed ## ]]" in user_content
+
+
+def test_chat_adapter_exception_raised_on_failure():
+    """
+    This test ensures that on an error, ChatAdapter raises an explicit exception.
+    """
+    signature = dspy.make_signature("question->answer")
+    adapter = dspy.ChatAdapter()
+    invalid_completion = "{'output':'mismatched value'}"
+    with pytest.raises(dspy.utils.exceptions.AdapterParseError, match="Adapter ChatAdapter failed to parse*"):
+        adapter.parse(signature, invalid_completion)
+
+
 def test_chat_adapter_formats_image():
     # Test basic image formatting
     image = dspy.Image(url="https://example.com/image.jpg")