test: add test for multiple predicates

tests/expr_and_series/when_test.py

@@ -9,7 +9,7 @@
 from tests.utils import compare_dicts
 
 data = {
-    "a": [1, 1, 2],
+    "a": [1, 2, 3],
     "b": ["a", "b", "c"],
     "c": [4.1, 5.0, 6.0],
     "d": [True, False, True],
@@ -23,11 +23,11 @@ def test_when(request: Any, constructor: Any) -> None:
     df = nw.from_native(constructor(data))
     result = df.with_columns(when(nw.col("a") == 1).then(value=3).alias("a_when"))
     expected = {
-        "a": [1, 1, 2],
+        "a": [1, 2, 3],
         "b": ["a", "b", "c"],
         "c": [4.1, 5.0, 6.0],
         "d": [True, False, True],
-        "a_when": [3, 3, None],
+        "a_when": [3, None, None],
     }
     compare_dicts(result, expected)
 
@@ -39,10 +39,28 @@ def test_when_otherwise(request: Any, constructor: Any) -> None:
     df = nw.from_native(constructor(data))
     result = df.with_columns(when(nw.col("a") == 1).then(3).otherwise(6).alias("a_when"))
     expected = {
-        "a": [1, 1, 2],
+        "a": [1, 2, 3],
         "b": ["a", "b", "c"],
         "c": [4.1, 5.0, 6.0],
         "d": [True, False, True],
-        "a_when": [3, 3, 6],
+        "a_when": [3, 6, 6],
+    }
+    compare_dicts(result, expected)
+
+
+def test_multiple_conditions(request: Any, constructor: Any) -> None:
+    if "pyarrow_table" in str(constructor):
+        request.applymarker(pytest.mark.xfail)
+
+    df = nw.from_native(constructor(data))
+    result = df.with_columns(
+        when(nw.col("a") < 3, nw.col("c") < 5.0).then(3).alias("a_when")
+    )
+    expected = {
+        "a": [1, 2, 3],
+        "b": ["a", "b", "c"],
+        "c": [4.1, 5.0, 6.0],
+        "d": [True, False, True],
+        "a_when": [3, None, None],
     }
     compare_dicts(result, expected)