PydanticOutputParser unit test (#2047)

Unit test for PydanticOutputParser

---------

Co-authored-by: Daniel Chalef <daniel.chalef@private.org>

tests/unit_tests/output_parsers/test_pydantic_parser.py

@@ -0,0 +1,67 @@
+"""Test PydanticOutputParser"""
+from enum import Enum
+from typing import Optional
+
+from pydantic import BaseModel, Field
+
+from langchain.output_parsers.pydantic import PydanticOutputParser
+from langchain.schema import OutputParserException
+
+
+class Actions(Enum):
+    SEARCH = "Search"
+    CREATE = "Create"
+    UPDATE = "Update"
+    DELETE = "Delete"
+
+
+class TestModel(BaseModel):
+    action: Actions = Field(description="Action to be performed")
+    action_input: str = Field(description="Input to be used in the action")
+    additional_fields: Optional[str] = Field(
+        description="Additional fields", default=None
+    )
+
+
+DEF_RESULT = """{
+    "action": "Update",
+    "action_input": "The PydanticOutputParser class is powerful",
+    "additional_fields": null
+}"""
+
+# action 'update' with a lowercase 'u' to test schema validation failure.
+DEF_RESULT_FAIL = """{
+    "action": "update",
+    "action_input": "The PydanticOutputParser class is powerful",
+    "additional_fields": null
+}"""
+
+DEF_EXPECTED_RESULT = TestModel(
+    action=Actions.UPDATE,
+    action_input="The PydanticOutputParser class is powerful",
+    additional_fields=None,
+)
+
+
+def test_pydantic_output_parser() -> None:
+    """Test PydanticOutputParser."""
+
+    pydantic_parser = PydanticOutputParser(pydantic_object=TestModel)
+
+    result = pydantic_parser.parse(DEF_RESULT)
+    print("parse_result:", result)
+    assert DEF_EXPECTED_RESULT == result
+
+
+def test_pydantic_output_parser_fail() -> None:
+    """Test PydanticOutputParser where completion result fails schema validation."""
+
+    pydantic_parser = PydanticOutputParser(pydantic_object=TestModel)
+
+    try:
+        pydantic_parser.parse(DEF_RESULT_FAIL)
+    except OutputParserException as e:
+        print("parse_result:", e)
+        assert "Failed to parse TestModel from completion" in str(e)
+    else:
+        assert False, "Expected OutputParserException"