utils: re-work the severity.db unit tests

This patch is a re-work of the severity_test.py tests, to break them
up into individual unit tests, and to add coverage for detecting
an invalid severity database (it does reduce the coverage for walking
profiles to find variable declarations, but that should be pulled out of
the severity handling code anyway).

Note that the last test case will fail, because even though the code
path in Severity.__init__() looks like it will return None if no path
is given, a Severity object in a half-state of initialization will
actually be returned.

Signed-off-by: Steve Beattie <steve@nxnw.org>
Acked-by: Christian Boltz <apparmor@cboltz.de>

utils/test/common_test.py

@@ -12,6 +12,7 @@
 #
 # ----------------------------------------------------------------------
 import unittest
+import os
 import re
 
 import apparmor.common
@@ -55,6 +56,13 @@ def setup_regex_tests(test_class):
         stub_test.__doc__ = "test '%s': %s" % (line, desc)
         setattr(test_class, 'test_%d' % (i), stub_test)
 
+def write_file(directory, file, contents):
+    '''construct path, write contents to it, and return the constructed path'''
+    path = os.path.join(directory, file)
+    with open(path, 'w+') as f:
+        f.write(contents)
+    return path
+
 if __name__ == "__main__":
     #import sys;sys.argv = ['', 'Test.test_RegexParser']
     unittest.main()