fix broken test

py-polars/tests/unit/io/test_lazy_csv.py

@@ -6,7 +6,6 @@
 import pytest
 
 import polars as pl
-from polars.exceptions import PolarsPanicError
 from polars.testing import assert_frame_equal
 
 if TYPE_CHECKING:
@@ -150,13 +149,14 @@ def test_scan_csv_schema_new_columns_dtypes(
         == df1.select(["sugars", pl.col("calories").cast(pl.Int64)]).rows()
     )
 
-    # expect same number of column names as there are columns in the file
-    with pytest.raises(PolarsPanicError, match="should be equal"):
-        pl.scan_csv(
-            file_path,
-            dtypes=[pl.Utf8, pl.Utf8],
-            new_columns=["category", "calories"],
-        ).collect()
+    # partially rename columns / overwrite dtypes
+    df4 = pl.scan_csv(
+        file_path,
+        dtypes=[pl.Utf8, pl.Utf8],
+        new_columns=["category", "calories"],
+    ).collect()
+    assert df4.dtypes == [pl.Utf8, pl.Utf8, pl.Float64, pl.Int64]
+    assert df4.columns == ["category", "calories", "fats_g", "sugars_g"]
 
     # cannot set both 'new_columns' and 'with_column_names'
     with pytest.raises(ValueError, match="mutually.exclusive"):