make pint optional for running tests

Author: DocOtak

gsw_xarray/tests/conftest.py

@@ -14,3 +14,9 @@ def ds():
     ds["SA"] = ds["id"] * 0.1 + 34
     ds["SA"].attrs = {"standard_name": "sea_water_absolute_salinity"}
     return ds
+
+
+@pytest.fixture(scope="session")
+def ureg():
+    pint = pytest.importorskip("pint")
+    return pint.UnitRegistry()

gsw_xarray/tests/test_units.py

@@ -6,13 +6,10 @@
 from .test_imports import gsw_base
 from gsw_xarray._attributes import _func_attrs
 
-from pint import UnitRegistry
-
-ureg = UnitRegistry()
-
 
 @pytest.mark.parametrize("func_name", gsw_base)
-def test_unit_pint(func_name):
+def test_unit_pint(func_name, ureg):
+
     if func_name in ["indexer", "match_args_return", "pchip_interp"]:
         # Internal gsw cookery or non wrapped functions
         return