Add tests for sorting and filtering with string expressions in DataFrame

Author: kosiew

python/tests/test_dataframe.py

@@ -268,6 +268,19 @@ def test_sort(df):
     assert table.to_pydict() == expected
 
 
+def test_sort_string_and_expression_equivalent(df):
+    from datafusion import col
+
+    result_str = df.sort("a").to_pydict()
+    result_expr = df.sort(col("a")).to_pydict()
+    assert result_str == result_expr
+
+
+def test_filter_string_unsupported(df):
+    with pytest.raises(AttributeError):
+        df.filter("a > 1")
+
+
 def test_drop(df):
     df = df.drop("c")