Use unittest.mock.patch.dict to set envvar

tests/test_coverity.py

@@ -2,7 +2,7 @@
 import os
 from io import StringIO
 from pathlib import Path
-from unittest import TestCase
+from unittest import TestCase, mock
 from unittest.mock import patch
 
 from mlx.warnings import WarningsPlugin, warnings_wrapper
@@ -19,19 +19,12 @@ def ordered(obj):
     else:
         return obj
 
-
+@mock.patch.dict(os.environ, {"MIN_COV_WARNINGS": "1", "MAX_COV_WARNINGS": "2"})
 class TestCoverityWarnings(TestCase):
     def setUp(self):
-        os.environ["MIN_COV_WARNINGS"] = "1"
-        os.environ["MAX_COV_WARNINGS"] = "2"
         self.warnings = WarningsPlugin(verbose=True)
         self.warnings.activate_checker_name('coverity')
 
-    def tearDown(self):
-        for var in ('MIN_POLY_WARNINGS', 'MAX_POLY_WARNINGS'):
-            if var in os.environ:
-                del os.environ[var]
-
     def test_no_warning_normal_text(self):
         dut = 'This should not be treated as warning'
         self.warnings.check(dut)
@@ -79,9 +72,9 @@ def test_code_quality_without_config(self):
             str(TEST_IN_DIR / 'defects.txt'),
         ])
         self.assertEqual(8, retval)
-        with open(out_file) as file:
+        with open(out_file) as file:
             cq_out = json.load(file)
-        with open(ref_file) as file:
+        with open(ref_file) as file:
             cq_ref = json.load(file)
         self.assertEqual(ordered(cq_out), ordered(cq_ref))
 
@@ -95,8 +88,8 @@ def test_code_quality_with_config(self):
             str(TEST_IN_DIR / 'defects.txt'),
         ])
         self.assertEqual(3, retval)
-        with open(out_file) as file:
+        with open(out_file) as file:
             cq_out = json.load(file)
-        with open(ref_file) as file:
+        with open(ref_file) as file:
             cq_ref = json.load(file)
         self.assertEqual(ordered(cq_out), ordered(cq_ref))