Assert warnings

Author: Aloqeely

pandas/tests/tools/test_to_datetime.py

@@ -3007,9 +3007,11 @@ def test_parsers_dayfirst_yearfirst(
             result2 = Timestamp(date_str)
             assert result2 == expected
 
-        result3 = to_datetime(
-            date_str, dayfirst=dayfirst, yearfirst=yearfirst, cache=cache
-        )
+        warn = UserWarning if dayfirst else None
+        with tm.assert_produces_warning(warn, match="Could not infer format"):
+            result3 = to_datetime(
+                date_str, dayfirst=dayfirst, yearfirst=yearfirst, cache=cache
+            )
 
         result4 = DatetimeIndex([date_str], dayfirst=dayfirst, yearfirst=yearfirst)[0]