Fix TypeError when faithfulness context chunk text is None

rag/evaluator/faithfulness_checker.py

@@ -34,8 +34,8 @@ def check(self, feedback: str, context_chunks: list[dict]) -> float:
             logger.info("faithfulness_no_claims_extracted")
             return 0.5  # Default to neutral if no extractable claims
 
-        # Concatenate context text
-        context_text = " ".join([chunk.get("text", "") for chunk in context_chunks])
+        # Concatenate context text; treat missing or None text as empty
+        context_text = " ".join([chunk.get("text") or "" for chunk in context_chunks])
 
         # Check each claim for support
         supported = 0

tests/unit/test_faithfulness_checker.py

@@ -222,21 +222,25 @@ def test_minimum_overlap_required(self, checker):
         assert isinstance(supported, bool)
         # Need at least 2 meaningful tokens for support
 
-    @pytest.mark.xfail(
-        strict=True,
-        reason="issue #60: faithfulness checker crashes when a context chunk has text: None",
-    )
     def test_none_context_chunk_text(self, checker):
         """Test handling of None in context chunk text."""
         feedback = "Has Python skills"
         context_chunks = [{"text": None}]
 
         score = checker.check(feedback, context_chunks)
 
-        # Should handle gracefully
+        # Should handle gracefully instead of raising TypeError
         assert isinstance(score, float)
         assert 0.0 <= score <= 1.0
 
+        # Mixed None and real text must also be join-safe
+        mixed_score = checker.check(
+            "Knows Python.",
+            [{"text": None}, {"text": "Knows Python well"}],
+        )
+        assert isinstance(mixed_score, float)
+        assert 0.0 <= mixed_score <= 1.0
+
     def test_missing_text_key_in_chunk(self, checker):
         """Test handling of missing 'text' key in context chunk."""
         feedback = "Has Python skills"