test files

tests/expr/fill_null_test.py

@@ -0,0 +1,32 @@
+from typing import Any
+
+import pandas as pd
+import polars as pl
+import pytest
+
+import narwhals as nw
+from tests.utils import compare_dicts
+
+data = {
+    "a": [0.0, None, 2, 3, 4],
+    "b": [1.0, None, None, 5, 3],
+    "c": [5.0, None, 3, 2, 1],
+}
+
+
+@pytest.mark.parametrize("constructor", [pd.DataFrame, pl.DataFrame])
+def test_over_single(constructor: Any) -> None:
+    df = nw.from_native(constructor(data), eager_only=True)
+    result = df.with_columns(nw.all().fill_null(99))
+    expected = {
+        "a": [0.0, 99, 2, 3, 4],
+        "b": [1.0, 99, 99, 5, 3],
+        "c": [5.0, 99, 3, 2, 1],
+    }
+    compare_dicts(result, expected)
+    result = df.with_columns(
+        a=df["a"].fill_null(99),
+        b=df["b"].fill_null(99),
+        c=df["c"].fill_null(99),
+    )
+    compare_dicts(result, expected)