Add tests for edge cases in sentiment prediction

Author: Pragya-19

tests/test_edge_cases.py

@@ -0,0 +1,11 @@
+from nlp_model.sentiment_model import predict_sentiment
+
+
+def test_empty_input():
+    result = predict_sentiment("")
+    assert result == "neutral"
+
+
+def test_numeric_input():
+    result = predict_sentiment("12345")
+    assert result == "neutral"