Fix Whisper JSON chunk extraction

tests/test_chunking.py

@@ -0,0 +1,50 @@
+import json
+import tempfile
+import unittest
+from pathlib import Path
+
+from src.meeting_lab.chunking.chunk_transcript import (
+    build_chunks,
+    read_transcript_blocks,
+    rendered_length,
+)
+
+
+class ChunkTranscriptTests(unittest.TestCase):
+    def test_whisper_json_uses_segments_not_aggregate_text(self) -> None:
+        data = {
+            "text": "alpha beta gamma",
+            "segments": [
+                {"text": "alpha"},
+                {"text": "beta"},
+                {"text": "gamma"},
+            ],
+        }
+        with tempfile.TemporaryDirectory() as directory:
+            input_file = Path(directory) / "meeting.json"
+            input_file.write_text(json.dumps(data), encoding="utf-8")
+
+            blocks = read_transcript_blocks(input_file)
+
+        self.assertEqual(blocks, ["alpha", "beta", "gamma"])
+        self.assertNotIn("alpha beta gamma", blocks)
+
+    def test_chunks_do_not_share_later_blocks_without_overlap(self) -> None:
+        blocks = [f"block-{number:02d}-" + ("x" * 20) for number in range(10)]
+
+        chunks = build_chunks(
+            blocks=blocks,
+            target_chars=60,
+            max_chars=80,
+            min_chars=30,
+            overlap_blocks=0,
+        )
+
+        flattened = [block for chunk in chunks for block in chunk]
+        self.assertEqual(flattened, blocks)
+        self.assertEqual(len(flattened), len(set(flattened)))
+        self.assertTrue(all(rendered_length(chunk) <= 80 for chunk in chunks))
+
+
+if __name__ == "__main__":
+    unittest.main()