Add test for aggregate method with string and expression equivalence

Author: kosiew

python/tests/test_dataframe.py

@@ -276,6 +276,14 @@ def test_sort_string_and_expression_equivalent(df):
     assert result_str == result_expr
 
 
+def test_aggregate_string_and_expression_equivalent(df):
+    from datafusion import col
+
+    result_str = df.aggregate("a", [f.count()]).to_pydict()
+    result_expr = df.aggregate(col("a"), [f.count()]).to_pydict()
+    assert result_str == result_expr
+
+
 def test_filter_string_unsupported(df):
     with pytest.raises(TypeError, match=r"col\(\) or lit\(\)"):
         df.filter("a > 1")