langchain: Use pytest.raises and pytest.fail to handle exceptions in tests (#31911)

Co-authored-by: Mason Daugherty <mason@langchain.dev>

libs/langchain/tests/unit_tests/agents/test_agent_iterator.py

@@ -305,7 +305,7 @@ def test_agent_iterator_output_structure() -> None:
         elif "output" in step:
             assert isinstance(step["output"], str)
         else:
-            assert False, "Unexpected output structure"
+            pytest.fail("Unexpected output structure")
 
 
 async def test_agent_async_iterator_output_structure() -> None:
@@ -321,7 +321,7 @@ async def test_agent_async_iterator_output_structure() -> None:
         elif "output" in step:
             assert isinstance(step["output"], str)
         else:
-            assert False, "Unexpected output structure"
+            pytest.fail("Unexpected output structure")
 
 
 def test_agent_iterator_empty_input() -> None:

libs/langchain/tests/unit_tests/output_parsers/test_datetime_parser.py

@@ -1,5 +1,7 @@
 from datetime import datetime
-from time import sleep
+
+import pytest
+from langchain_core.exceptions import OutputParserException
 
 from langchain.output_parsers.datetime import DatetimeOutputParser
 
@@ -39,11 +41,5 @@ def test_datetime_output_parser_parse() -> None:
     )
 
     # Test invalid input
-    try:
+    with pytest.raises(OutputParserException):
-        sleep(0.001)
+        parser.parse("Invalid date string")
-        datestr = date.strftime(parser.format)
-        result = parser.parse(datestr)
-        assert result == date
-        assert False, "Should have raised AssertionError"
-    except AssertionError:
-        pass

libs/langchain/tests/unit_tests/output_parsers/test_enum_parser.py

@@ -1,5 +1,6 @@
 from enum import Enum
 
+import pytest
 from langchain_core.exceptions import OutputParserException
 
 from langchain.output_parsers.enum import EnumOutputParser
@@ -25,11 +26,8 @@ def test_enum_output_parser_parse() -> None:
     assert result == Colors.BLUE
 
     # Test invalid input
-    try:
+    with pytest.raises(OutputParserException):
         parser.parse("INVALID")
-        assert False, "Should have raised OutputParserException"
-    except OutputParserException:
-        pass
 
 
 def test_enum_output_parser_output_type() -> None:

libs/langchain/tests/unit_tests/output_parsers/test_pandas_dataframe_parser.py

@@ -3,6 +3,7 @@
 from typing import Any
 
 import pandas as pd
+import pytest
 from langchain_core.exceptions import OutputParserException
 
 from langchain.output_parsers.pandas_dataframe import PandasDataFrameOutputParser
@@ -20,20 +21,14 @@ parser = PandasDataFrameOutputParser(dataframe=df)
 
 # Test Invalid Column
 def test_pandas_output_parser_col_no_array() -> None:
-    try:
+    with pytest.raises(OutputParserException):
         parser.parse("column:num_legs")
-        assert False, "Should have raised OutputParserException"
-    except OutputParserException:
-        assert True
 
 
 # Test Column with invalid array (above DataFrame max index)
 def test_pandas_output_parser_col_oob() -> None:
-    try:
+    with pytest.raises(OutputParserException):
         parser.parse("row:10")
-        assert False, "Should have raised OutputParserException"
-    except OutputParserException:
-        assert True
 
 
 # Test Column with array [x]
@@ -53,11 +48,8 @@ def test_pandas_output_parser_col_multi_elem() -> None:
 
 # Test Row with invalid row entry
 def test_pandas_output_parser_row_no_array() -> None:
-    try:
+    with pytest.raises(OutputParserException):
         parser.parse("row:5")
-        assert False, "Should have raised OutputParserException"
-    except OutputParserException:
-        assert True
 
 
 # Test Row with valid row entry
@@ -69,11 +61,8 @@ def test_pandas_output_parser_row_first() -> None:
 
 # Test Row with invalid col entry
 def test_pandas_output_parser_row_no_column() -> None:
-    try:
+    with pytest.raises(OutputParserException):
         parser.parse("row:1[num_legs]")
-        assert False, "Should have raised OutputParserException"
-    except OutputParserException:
-        assert True
 
 
 # Test Row with valid col entry
@@ -110,11 +99,8 @@ def test_pandas_output_parser_special_ops() -> None:
 
 
 def test_pandas_output_parser_invalid_special_op() -> None:
-    try:
+    with pytest.raises(OutputParserException):
         parser.parse("riemann_sum:chicken")
-        assert False, "Should have raised OutputParserException"
-    except OutputParserException:
-        assert True
 
 
 def test_pandas_output_parser_output_type() -> None: