Fix flaky regrid test by clearing LRU cache after each test (#2322)

Co-authored-by: Manuel Schlund <[email protected]>

tests/unit/preprocessor/_regrid/test__stock_cube.py

@@ -85,6 +85,10 @@ def setUp(self):
  'iris.coords.DimCoord', return_value=self.mock_coord)
  self.mocks = [self.mock_Cube, self.mock_coord, self.mock_DimCoord]
 
+ def tearDown(self) -> None:
+ _global_stock_cube.cache_clear()
+ return super().tearDown()
+
  def test_invalid_cell_spec__alpha(self):
  emsg = 'Invalid MxN cell specification'
  with self.assertRaisesRegex(ValueError, emsg):

tests/unit/preprocessor/_regrid/test_extract_regional_grid.py

@@ -11,6 +11,18 @@
  regrid,
 )
 
+
+@pytest.fixture(autouse=True)
+def clear_lru_cache():
+ """Make sure to clear LRU cache for ``_global_stock_cube``.
+
+ See https://github.com/ESMValGroup/ESMValCore/issues/2320.
+
+ """
+ yield # execute tests
+ _global_stock_cube.cache_clear()
+
+
 SPEC_KEYS = ('start_longitude', 'end_longitude', 'step_longitude',
  'start_latitude', 'end_latitude', 'step_latitude')
 PASSING_SPECS = tuple(
@@ -44,7 +56,6 @@
  ))
 
 
-@pytest.mark.xfail
 @pytest.mark.parametrize('spec', PASSING_SPECS)
 def test_extract_regional_grid_passing(spec):
  """Test regridding with regional target spec."""