Remove hamming option from string distance tests (#9882)

Description: We should not test Hamming string distance for strings that
are not equal length, since this is not defined. Removing hamming
distance tests for unequal string distances.

libs/langchain/tests/unit_tests/evaluation/string_distance/test_base.py

@@ -56,8 +56,13 @@ async def test_zero_distance_pairwise_async(distance: StringDistance) -> None:
     assert result["score"] == 0
 
 
+valid_distances = [
+    distance for distance in StringDistance if distance != StringDistance.HAMMING
+]
+
+
 @pytest.mark.requires("rapidfuzz")
-@pytest.mark.parametrize("distance", list(StringDistance))
+@pytest.mark.parametrize("distance", valid_distances)
 @pytest.mark.parametrize("normalize_score", [True, False])
 def test_non_zero_distance(distance: StringDistance, normalize_score: bool) -> None:
     eval_chain = StringDistanceEvalChain(
@@ -74,7 +79,7 @@ def test_non_zero_distance(distance: StringDistance, normalize_score: bool) -> N
 
 @pytest.mark.asyncio
 @pytest.mark.requires("rapidfuzz")
-@pytest.mark.parametrize("distance", list(StringDistance))
+@pytest.mark.parametrize("distance", valid_distances)
 async def test_non_zero_distance_async(distance: StringDistance) -> None:
     eval_chain = StringDistanceEvalChain(distance=distance)
     prediction = "I like to eat apples."
@@ -87,7 +92,7 @@ async def test_non_zero_distance_async(distance: StringDistance) -> None:
 
 
 @pytest.mark.requires("rapidfuzz")
-@pytest.mark.parametrize("distance", list(StringDistance))
+@pytest.mark.parametrize("distance", valid_distances)
 def test_non_zero_distance_pairwise(distance: StringDistance) -> None:
     eval_chain = PairwiseStringDistanceEvalChain(distance=distance)
     prediction = "I like to eat apples."
@@ -101,7 +106,7 @@ def test_non_zero_distance_pairwise(distance: StringDistance) -> None:
 
 @pytest.mark.asyncio
 @pytest.mark.requires("rapidfuzz")
-@pytest.mark.parametrize("distance", list(StringDistance))
+@pytest.mark.parametrize("distance", valid_distances)
 async def test_non_zero_distance_pairwise_async(distance: StringDistance) -> None:
     eval_chain = PairwiseStringDistanceEvalChain(distance=distance)
     prediction = "I like to eat apples."