Address code coverage in tests

src/nested_pandas/nestedframe/core.py

@@ -872,7 +872,7 @@ def reduce(self, func, *args, **kwargs) -> NestedFrame:  # type: ignore[override
         Takes a function and applies it to each top-level row of the NestedFrame.
 
         The user may specify which columns the function is applied to, with
-        columns from the 'base' layer being passsed to the function as
+        columns from the 'base' layer being passed to the function as
         scalars and columns from the nested layers being passed as numpy arrays.
 
         Parameters

tests/nested_pandas/nestedframe/test_nestedframe.py

@@ -870,6 +870,14 @@ def offset_avg(offset, col_to_avg, column_names):
     for i in range(len(result)):
         assert result["offset_avg"].values[i] == expected_offset_avg[i]
 
+    # Verify that we can understand a string argument to the reduce function,
+    # so long as it isn't a column name.
+    def make_id(col1, prefix_str):
+        return f"{prefix_str}{col1}"
+
+    result = nf.reduce(make_id, "b", "some_id_")
+    assert result[0][1] == "some_id_4"
+
 
 def test_reduce_duplicated_cols():
     """Tests nf.reduce() to correctly handle duplicated column names."""