add test, fix assert spacing, remove unnecessary coalesce

Author: TrevorBergeron

bigframes/core/compile/ibis_compiler/scalar_op_registry.py

@@ -1062,7 +1062,7 @@ def isin_op_impl(x: ibis_types.Value, op: ops.IsInOp):
     if op.match_nulls and contains_nulls:
         return x.isnull() | x.isin(matchable_ibis_values)
     else:
-        return x.isin(matchable_ibis_values).fillna(False)
+        return x.isin(matchable_ibis_values)
 
 
 @scalar_op_compiler.register_unary_op(ops.ToDatetimeOp, pass_op=True)

tests/system/small/engines/test_generic_ops.py

@@ -421,4 +421,5 @@ def test_engines_isin_op(scalars_array_value: array_value.ArrayValue, engine):
     arr = arr.rename_columns(
         {old_name: new_names[i] for i, old_name in enumerate(col_ids)}
     )
+
     assert_equivalence_execution(arr.node, REFERENCE_ENGINE, engine)

tests/system/small/test_dataframe.py

@@ -1591,7 +1591,7 @@ def test_itertuples(scalars_df_index, index, name):
         assert bf_tuple == pd_tuple
 
 
-def test_df_isin_list(scalars_dfs):
+def test_df_isin_list_w_null(scalars_dfs):
     scalars_df, scalars_pandas_df = scalars_dfs
     values = ["Hello, World!", 55555, 2.51, pd.NA, True]
     bf_result = (
@@ -1606,6 +1606,21 @@ def test_df_isin_list(scalars_dfs):
     pandas.testing.assert_frame_equal(bf_result, pd_result.astype("boolean"))
 
 
+def test_df_isin_list_wo_null(scalars_dfs):
+    scalars_df, scalars_pandas_df = scalars_dfs
+    values = ["Hello, World!", 55555, 2.51, True]
+    bf_result = (
+        scalars_df[["int64_col", "float64_col", "string_col", "bool_col"]]
+        .isin(values)
+        .to_pandas()
+    )
+    pd_result = scalars_pandas_df[
+        ["int64_col", "float64_col", "string_col", "bool_col"]
+    ].isin(values)
+
+    pandas.testing.assert_frame_equal(bf_result, pd_result.astype("boolean"))
+
+
 def test_df_isin_dict(scalars_dfs):
     scalars_df, scalars_pandas_df = scalars_dfs
     values = {