Filter for only allowed engine keywords

src/rechunk_data/tests/test_rechunk_netcdf.py

 """Test the actual rechunk method."""
 import logging
-from tempfile import NamedTemporaryFile, TemporaryDirectory
 from pathlib import Path
+import time
+from tempfile import NamedTemporaryFile, TemporaryDirectory
 
 import dask
+import pytest
 from rechunk_data import rechunk_netcdf_file, rechunk_dataset
 from rechunk_data._rechunk import _save_dataset
 
@@ -30,10 +32,11 @@ def test_rechunk_data_dir_without_overwrite(data_dir: Path) -> None:
 def test_rechunk_single_data_file(data_file: Path) -> None:
     """Testing rechunking of single data files."""
 
-    a_time = float(data_file.stat().st_atime)
+    a_time = float(data_file.stat().st_mtime)
+    time.sleep(0.5)
     with dask.config.set({"array.chunk-size": "1MiB"}):
         rechunk_netcdf_file(data_file)
-        assert a_time < float(data_file.stat().st_atime)
+        assert a_time < float(data_file.stat().st_mtime)
         with NamedTemporaryFile(suffix=".nc") as temp_file:
             rechunk_netcdf_file(data_file, Path(temp_file.name))
             assert Path(temp_file.name).exists()
@@ -61,3 +64,9 @@ def test_wrong_or_format(small_chunk_data, caplog) -> None:
         _save_dataset(small_chunk_data, temp_file, {"foo": "bar"}, "foo")
         _, loglevel, message = caplog.record_tuples[-1]
         assert loglevel == logging.ERROR
+
+
+def test_wrong_engine(small_chunk_data) -> None:
+
+    with pytest.raises(ValueError):
+        rechunk_dataset(small_chunk_data, engine="foo")