fix version comparison checks in tests.

Author: jswhit2

Changelog

@@ -2,6 +2,8 @@
  =================================
  * make sure zstd compression filter test always runs unless specifically disabled, fix cli test so it runs on
  32-bit x86.  New wheels for linux that include plugins (they were left out of the 1.7.5 release).
+ * fix version comparison logic that was broken when using netcdf-c >= 4.10.0 - this was the cause of 
+ issue #1515 (diskless persisted datasets are no longer persisted).
 
  version 1.7.5 (tag v1.7.5rel)
  =============================

test/test_masked5.py

@@ -1,6 +1,7 @@
 import unittest
 import os
 import tempfile
+from packaging.version import Version
 
 import numpy as np
 from numpy import ma
@@ -55,7 +56,7 @@ def test_scaled(self):
         # issue 730
         # this part fails with netcdf 4.1.3
         # a bug in vlen strings?
-        if __netcdf4libversion__ >= '4.4.0':
+        if Version(__netcdf4libversion__) >= Version('4.4.0'):
             assert v2[0] == 'first'
             assert v2[1] == '<missing>'
 

test/test_vlen.py

@@ -2,6 +2,7 @@
 import unittest
 import os
 import tempfile
+from packaging.version import Version
 from netCDF4 import Dataset
 import numpy as np
 from numpy.testing import assert_array_equal
@@ -163,7 +164,7 @@ class VlenAppendTestCase(unittest.TestCase):
     def setUp(self):
 
         import netCDF4
-        if netCDF4.__netcdf4libversion__ < "4.4.1":
+        if Version(netCDF4.__netcdf4libversion__) < Version("4.4.1"):
             self.skip = True
             try:
                 self.skipTest("This test requires NetCDF 4.4.1 or later.")