Refactor assertGivesWarning into separate methods

lib/iris/tests/__init__.py

@@ -539,26 +539,37 @@ def assertRaisesRegexp(self, *args, **kwargs):
                                      *args, **kwargs)
 
     @contextlib.contextmanager
-    def assertGivesWarning(self, expected_regexp='', expect_warning=True):
-        # Check that a warning is raised matching a given expression, or that
-        # no warning matching the given expression is raised.
+    def _recordWarningMatches(self, expected_regexp=''):
+        # Record warnings raised matching a given expression.
+        matches = []
         with warnings.catch_warnings(record=True) as w:
             warnings.simplefilter('always')
-            yield
+            yield matches
         messages = [str(warning.message) for warning in w]
         expr = re.compile(expected_regexp)
-        matches = [message for message in messages if expr.search(message)]
-        warning_raised = any(matches)
-        if expect_warning:
-            if not warning_raised:
-                msg = "Warning matching '{}' not raised."
-                msg = msg.format(expected_regexp)
-                self.assertEqual(expect_warning, warning_raised, msg)
-        else:
-            if warning_raised:
-                msg = "Unexpected warning(s) raised, matching '{}' : {!r}."
-                msg = msg.format(expected_regexp, matches)
-                self.assertEqual(expect_warning, warning_raised, msg)
+        matches.extend(message for message in messages
+                        if expr.search(message))
+
+    @contextlib.contextmanager
+    def assertGivesWarning(self, expected_regexp=''):
+        # Check that a warning is raised matching a given expression.
+        with self._recordWarningMatches(expected_regexp) as matches:
+            yield
+
+        msg = "Warning matching '{}' not raised."
+        msg = msg.format(expected_regexp)
+        self.assertTrue(matches, msg)
+
+
+    @contextlib.contextmanager
+    def assertDoesNotGiveWarning(self, expected_regexp=''):
+        # Check that no warning matching the given expression is raised.
+        with self._recordWarningMatches(expected_regexp) as matches:
+            yield
+
+        msg = "Unexpected warning(s) raised, matching '{}' : {!r}."
+        msg = msg.format(expected_regexp, matches)
+        self.assertFalse(matches, msg)
 
     def _assertMaskedArray(self, assertion, a, b, strict, **kwargs):
         # Define helper function to extract unmasked values as a 1d

lib/iris/tests/unit/fileformats/netcdf/test_Saver.py

@@ -440,7 +440,7 @@ def test_contains_default_fill_value_byte(self):
         # value if no fill_value argument is supplied when the data is of a
         # byte type.
         cube = self._make_cube('>i1')
-        with self.assertGivesWarning(r'\(fill\|mask\)', expect_warning=False):
+        with self.assertDoesNotGiveWarning(r'\(fill\|mask\)'):
             with self._netCDF_var(cube):
                 pass
 
@@ -449,15 +449,15 @@ def test_contains_masked_fill_value(self):
         # a masked point.
         fill_value = 1
         cube = self._make_cube('>f4', masked_value=fill_value)
-        with self.assertGivesWarning(r'\(fill\|mask\)', expect_warning=False):
+        with self.assertDoesNotGiveWarning(r'\(fill\|mask\)'):
             with self._netCDF_var(cube, fill_value=fill_value):
                 pass
 
     def test_masked_byte_default_fill_value(self):
         # Test that a warning is raised when saving masked byte data with no
         # fill value supplied.
         cube = self._make_cube('>i1', masked_value=1)
-        with self.assertGivesWarning(r'\(fill\|mask\)', expect_warning=False):
+        with self.assertDoesNotGiveWarning(r'\(fill\|mask\)'):
             with self._netCDF_var(cube):
                 pass
 
@@ -466,7 +466,7 @@ def test_masked_byte_fill_value_passed(self):
         # fill value supplied if the the data does not contain the fill_value.
         fill_value = 100
         cube = self._make_cube('>i1', masked_value=2)
-        with self.assertGivesWarning(r'\(fill\|mask\)', expect_warning=False):
+        with self.assertDoesNotGiveWarning(r'\(fill\|mask\)'):
             with self._netCDF_var(cube, fill_value=fill_value):
                 pass
 

lib/iris/tests/unit/fileformats/pp/test_PPField.py

@@ -146,7 +146,7 @@ def test_mdi_masked_value_nowarning(self):
         # Set underlying data value at masked point to BMDI value.
         field.data.data[1] = field.bmdi
         self.assertArrayAllClose(field.data.data[1], field.bmdi)
-        with self.assertGivesWarning(r'\(mask\|fill\)', expect_warning=False):
+        with self.assertDoesNotGiveWarning(r'\(mask\|fill\)'):
             with self.temp_filename('.pp') as temp_filename:
                 with open(temp_filename, 'wb') as pp_file:
                     field.save(pp_file)