Improve SimpleTextAggregator to handle multi-sentence chunks

tests/test_simple_text_aggregator.py

@@ -19,11 +19,39 @@ class TestSimpleTextAggregator(unittest.IsolatedAsyncioTestCase):
         await self.aggregator.reset()
         assert self.aggregator.text == ""
 
-    async def test_simple_sentence(self):
-        assert await self.aggregator.aggregate("Hello ") == None
-        assert await self.aggregator.aggregate("Pipecat!") == "Hello Pipecat!"
+    async def test_word_by_word(self):
+        """Test word-by-word token aggregation (e.g., OpenAI)."""
+        assert await self.aggregator.aggregate("Hello") == None
+        assert await self.aggregator.aggregate("!") == "Hello!"
+        assert await self.aggregator.aggregate(" I") == None
+        assert await self.aggregator.aggregate(" am") == None
+        assert await self.aggregator.aggregate(" Doug.") == " I am Doug."
         assert self.aggregator.text == ""
 
-    async def test_multiple_sentences(self):
-        assert await self.aggregator.aggregate("Hello Pipecat! How are ") == "Hello Pipecat!"
-        assert await self.aggregator.aggregate("you?") == " How are you?"
+    async def test_chunks_with_partial_sentences(self):
+        """Test chunks with partial sentences."""
+        assert await self.aggregator.aggregate("Hey!") == "Hey!"
+        assert await self.aggregator.aggregate(" Nice to meet you! So") == " Nice to meet you!"
+        assert self.aggregator.text == " So"
+        assert await self.aggregator.aggregate(" what") == None
+        assert await self.aggregator.aggregate("'d you like?") == " So what'd you like?"
+
+    async def test_multi_sentence_chunk(self):
+        """Test chunks with multiple complete sentences."""
+        result = await self.aggregator.aggregate("Hello! I am Doug. Nice to meet you!")
+        assert result == "Hello!"
+        # Drain remaining sentences
+        assert await self.aggregator.flush_next_sentence() == " I am Doug."
+        assert await self.aggregator.flush_next_sentence() == " Nice to meet you!"
+        assert await self.aggregator.flush_next_sentence() == None
+        assert self.aggregator.text == ""
+
+    async def test_flush_next_sentence_with_incomplete(self):
+        """Test flush_next_sentence with incomplete sentence in buffer."""
+        assert await self.aggregator.aggregate("Hello! I am") == "Hello!"
+        assert await self.aggregator.flush_next_sentence() == None
+        assert self.aggregator.text == " I am"
+
+    async def test_flush_next_sentence_empty_buffer(self):
+        """Test flush_next_sentence with empty buffer."""
+        assert await self.aggregator.flush_next_sentence() == None