add more tests for narwhals.dataframe

Author: raisa

Diff for: tests/test_common.py

@@ -2,6 +2,7 @@
 
 from typing import Any
 
+import numpy as np
 import pandas as pd
 import polars as pl
 import pytest
@@ -119,3 +120,48 @@ def test_double_selected(df_raw: Any) -> None:
     result_native = nw.to_native(result)
     expected = {"a": [2, 6, 4], "b": [8, 8, 12]}
     compare_dicts(result_native, expected)
+
+
+@pytest.mark.parametrize("df_raw", [df_pandas, df_polars, df_lazy])
+def test_rename(df_raw: Any) -> None:
+    df = nw.DataFrame(df_raw)
+    result = df.rename({"a": "x", "b": "y"})
+    result_native = nw.to_native(result)
+    expected = {"x": [1, 3, 2], "y": [4, 4, 6], "z": [7.0, 8, 9]}
+    compare_dicts(result_native, expected)
+
+
+@pytest.mark.parametrize("df_raw", [df_pandas, df_polars, df_lazy])
+def test_join(df_raw: Any) -> None:
+    df = nw.DataFrame(df_raw)
+    df_right = df.rename({"z": "z_right"})
+    result = df.join(df_right, left_on=["a", "b"], right_on=["a", "b"], how="inner")
+    result_native = nw.to_native(result)
+    expected = {"a": [1, 3, 2], "b": [4, 4, 6], "z": [7.0, 8, 9], "z_right": [7.0, 8, 9]}
+    compare_dicts(result_native, expected)
+
+
+@pytest.mark.parametrize("df_raw", [df_pandas, df_polars, df_lazy])
+def test_schema(df_raw: Any) -> None:
+    df = nw.DataFrame(df_raw)
+    result = df.schema
+    expected = {"a": nw.dtypes.Int64, "b": nw.dtypes.Int64, "z": nw.dtypes.Float64}
+    assert result == expected
+
+
+@pytest.mark.parametrize("df_raw", [df_pandas, df_polars, df_lazy])
+def test_columns(df_raw: Any) -> None:
+    df = nw.DataFrame(df_raw)
+    result = df.columns
+    expected = ["a", "b", "z"]
+    assert len(result) == len(expected)
+    assert all(x == y for x, y in zip(result, expected))
+
+
+def test_accepted_dataframes() -> None:
+    array = np.array([[0, 4.0], [2, 5]])
+    with pytest.raises(
+        TypeError,
+        match="Expected pandas or Polars dataframe or lazyframe, got: <class 'numpy.ndarray'>",
+    ):
+        nw.DataFrame(array)