Refactor: Move clean_result out of TestEmails class

The `clean_result` method in `test/test.py` did not use any
instance-specific data, so it has been refactored into a
standalone function. This improves code clarity and modularity.

The associated regular expressions have also been moved to the
module level.

Author: mcepl

test/test.py

@@ -57,6 +57,51 @@ def load_tests(loader, tests, ignore):
 # This metaclass lets us generate the tests for each feed directory
 # separately. This lets us see which tests are being run more clearly than
 # if we had one big test that ran everything.
+MESSAGE_ID_REGEXP = _re.compile(
+    r'^Message-ID: <(.*)@{}>$'.format(_re.escape(platform.node())), _re.MULTILINE)
+USER_AGENT_REGEXP = _re.compile(
+    r'^User-Agent: rss2email/{0} \({1}\)$'.format(
+        _re.escape(_rss2email.__version__),
+        _re.escape(_rss2email.__url__)),
+    _re.MULTILINE)
+BOUNDARY_REGEXP = _re.compile('===============[^=]+==')
+
+
+def clean_result(text, regexes=None):
+    """Cleanup dynamic portions of the generated email headers
+
+    >>> text = (
+    ...      'Content-Type: multipart/digest;\\n'
+    ...      '  boundary="===============7509425281347501533=="\\n'
+    ...      'MIME-Version: 1.0\\n'
+    ...      'Date: Tue, 23 Aug 2011 15:57:37 -0000\\n'
+    ...      'Message-ID: <[email protected]>\\n'
+    ...      'User-Agent: rss2email/3.5 (https://github.com/rss2email/rss2email)\\n'
+    ...      )
+    >>> regexes = [
+    ...     (_re.compile(r'^Message-ID: <.*>$', _re.MULTILINE), 'Message-ID: <[email protected]>'),
+    ...     (_re.compile(r'^User-Agent: .*$', _re.MULTILINE), 'User-Agent: rss2email/...'),
+    ...     (_re.compile('===============[^=]+=='), '===============...=='),
+    ... ]
+    >>> print(clean_result(text, regexes).rstrip())
+    Content-Type: multipart/digest;
+      boundary="===============...=="
+    MIME-Version: 1.0
+    Date: Tue, 23 Aug 2011 15:57:37 -0000
+    Message-ID: <[email protected]>
+    User-Agent: rss2email/...
+    """
+    if regexes is None:
+        regexes = [
+            (MESSAGE_ID_REGEXP, 'Message-ID: <[email protected]>'),
+            (USER_AGENT_REGEXP, 'User-Agent: rss2email/...'),
+            (BOUNDARY_REGEXP, '===============...=='),
+        ]
+    for regexp,replacement in regexes:
+        text = regexp.sub(replacement, text)
+    return text
+
+
 class TestEmailsMeta(type):
     def __new__(cls, name, bases, attrs):
         # no paths on the command line, find all subdirectories
@@ -101,40 +146,6 @@ def __init__(self, *args, **kwargs):
         self.BASE_CONFIG_STRING = _stringio.getvalue()
         del _stringio
 
-        self.MESSAGE_ID_REGEXP = _re.compile(
-            r'^Message-ID: <(.*)@{}>$'.format(_re.escape(platform.node())), _re.MULTILINE)
-        self.USER_AGENT_REGEXP = _re.compile(
-            r'^User-Agent: rss2email/{0} \({1}\)$'.format(_re.escape(_rss2email.__version__), _re.escape(_rss2email.__url__)),
-            _re.MULTILINE)
-        self.BOUNDARY_REGEXP = _re.compile('===============[^=]+==')
-
-    def clean_result(self, text):
-        """Cleanup dynamic portions of the generated email headers
-
-        >>> text = (
-        ...      'Content-Type: multipart/digest;\\n'
-        ...      '  boundary="===============7509425281347501533=="\\n'
-        ...      'MIME-Version: 1.0\\n'
-        ...      'Date: Tue, 23 Aug 2011 15:57:37 -0000\\n'
-        ...      'Message-ID: <[email protected]>\\n'
-        ...      'User-Agent: rss2email/3.5 (https://github.com/rss2email/rss2email)\\n'
-        ...      )
-        >>> print(clean_result(text).rstrip())
-        Content-Type: multipart/digest;
-        boundary="===============...=="
-        MIME-Version: 1.0
-        Date: Tue, 23 Aug 2011 15:57:37 -0000
-        Message-ID: <[email protected]>
-        User-Agent: rss2email/...
-        """
-        for regexp,replacement in [
-                (self.MESSAGE_ID_REGEXP, 'Message-ID: <[email protected]>'),
-                (self.USER_AGENT_REGEXP, 'User-Agent: rss2email/...'),
-                (self.BOUNDARY_REGEXP, '===============...=='),
-        ]:
-            text = regexp.sub(replacement, text)
-        return text
-
     def run_single_test(self, dirname=None, config_path=None):
         if dirname is None:
             dirname = _os.path.dirname(config_path)
@@ -153,7 +164,7 @@ def run_single_test(self, dirname=None, config_path=None):
         feed._send = TestEmails.Send()
         feed.run()
         generated = feed._send.as_string()
-        generated = self.clean_result(generated)
+        generated = clean_result(generated)
 
         expected_path = config_path.replace('config', 'expected')
         if not _os.path.exists(expected_path):