test: add test

Author: mafaldam

pandas/_libs/tslibs/timedeltas.pyx

@@ -369,7 +369,6 @@ cdef convert_to_timedelta64(object ts, str unit):
         raise TypeError(f"Invalid type for timedelta scalar: {type(ts)}")
     return ts.astype("timedelta64[ns]")
 
-
 cdef create_timedelta_from_parts(
     int64_t days=0, int64_t hours=0, int64_t minutes=0, int64_t seconds=0,
     int64_t milliseconds=0, int64_t microseconds=0, int64_t nanoseconds=0):

pandas/tests/scalar/timedelta/test_timedelta.py

@@ -682,6 +682,12 @@ def test_replace_single_field(self):
         td = Timedelta(days=1, hours=5, minutes=45, seconds=30, milliseconds=250, 
             microseconds=125, nanoseconds=60)
 
+        # Test replacing only days
+        replaced = td.replace(days=2)
+        expected = Timedelta(days=2, hours=5, minutes=45, seconds=30, milliseconds=250, 
+            microseconds=125, nanoseconds=60)
+        assert replaced == expected, f"Expected {expected}, but got {replaced}"
+
         # Test replacing only seconds
         replaced = td.replace(seconds=45)
         expected = Timedelta(days=1, hours=5, minutes=45, seconds=45, milliseconds=250,