Make use of argparse groups and add some tests

This change makes use of argparse groups to generate error
messages when the user specifies invalid command line option
combinations.  For example if the user specified --pretty
and --no-pretty before it would not complain, but now it
will.

Change-Id: I07e1edb5c43ff7b0a81879f388770fb732fed43b

os_testr/os_testr.py

@@ -23,7 +23,7 @@ from subunit import run as subunit_run
 from testtools import run as testtools_run
 
 
-def parse_args():
+def get_parser():
     parser = argparse.ArgumentParser(
         description='Tool to run openstack tests')
     parser.add_argument('--blacklist_file', '-b',
@@ -42,27 +42,30 @@ def parse_args():
                             "discover and just excute the test specified. "
                             "A file name may be used in place of a test "
                             "name.")
-    parser.add_argument('--pretty', '-p', dest='pretty', action='store_true',
+    pretty = parser.add_mutually_exclusive_group()
+    pretty.add_argument('--pretty', '-p', dest='pretty', action='store_true',
                         help='Print pretty output from subunit-trace. This is '
                              'mutually exclusive with --subunit')
-    parser.add_argument('--no-pretty', dest='pretty', action='store_false',
+    pretty.add_argument('--no-pretty', dest='pretty', action='store_false',
                         help='Disable the pretty output with subunit-trace')
     parser.add_argument('--subunit', '-s', action='store_true',
                         help='output the raw subunit v2 from the test run '
-                             'this is mutuall exclusive with --pretty')
+                             'this is mutually exclusive with --pretty')
     parser.add_argument('--list', '-l', action='store_true',
                         help='List all the tests which will be run.')
-    parser.add_argument('--slowest', dest='slowest', action='store_true',
-                        help="after the test run print the slowest tests")
-    parser.add_argument('--no-slowest', dest='slowest', action='store_false',
-                        help="after the test run don't print the slowest "
-                             "tests")
+    slowest = parser.add_mutually_exclusive_group()
+    slowest.add_argument('--slowest', dest='slowest', action='store_true',
+                         help="after the test run print the slowest tests")
+    slowest.add_argument('--no-slowest', dest='slowest', action='store_false',
+                         help="after the test run don't print the slowest "
+                              "tests")
     parser.add_argument('--pdb', metavar='TEST_ID',
                         help='Run a single test that has pdb traces added')
-    parser.add_argument('--parallel', dest='parallel', action='store_true',
-                        help='Run tests in parallel (this is the default)')
-    parser.add_argument('--serial', dest='parallel', action='store_false',
-                        help='Run tests serially')
+    parallel = parser.add_mutually_exclusive_group()
+    parallel.add_argument('--parallel', dest='parallel', action='store_true',
+                          help='Run tests in parallel (this is the default)')
+    parallel.add_argument('--serial', dest='parallel', action='store_false',
+                          help='Run tests serially')
     parser.add_argument('--concurrency', '-c', type=int, metavar='WORKERS',
                         help='The number of workers to use when running in '
                              'parallel. By default this is the number of cpus')
@@ -76,8 +79,7 @@ def parse_args():
                              'prints the comment from the same line and all '
                              'skipped tests before the test run')
     parser.set_defaults(pretty=True, slowest=True, parallel=True)
-    opts = parser.parse_args()
-    return opts
+    return parser
 
 
 def _get_test_list(regex, env=None):
@@ -239,7 +241,7 @@ def call_testtools_run(test_id):
 
 
 def main():
-    opts = parse_args()
+    opts = get_parser().parse_args()
     if opts.pretty and opts.subunit:
         msg = ('Subunit output and pretty output cannot be specified at the '
                'same time')

os_testr/tests/test_os_testr.py

@@ -23,10 +23,36 @@ from os_testr import os_testr
 from os_testr.tests import base
 
 
-class Test_Construct_Regex(base.TestCase):
+class TestPathToRegex(base.TestCase):
 
     def test_file_name(self):
         result = os_testr.path_to_regex("tests/network/v2/test_net.py")
         self.assertEqual("tests.network.v2.test_net", result)
         result = os_testr.path_to_regex("openstack/tests/network/v2")
         self.assertEqual("openstack.tests.network.v2", result)
+
+
+class TestGetParser(base.TestCase):
+    def test_pretty(self):
+        namespace = os_testr.get_parser().parse_args(['--pretty'])
+        self.assertEqual(True, namespace.pretty)
+        namespace = os_testr.get_parser().parse_args(['--no-pretty'])
+        self.assertEqual(False, namespace.pretty)
+        self.assertRaises(SystemExit, os_testr.get_parser().parse_args,
+                          ['--no-pretty', '--pretty'])
+
+    def test_slowest(self):
+        namespace = os_testr.get_parser().parse_args(['--slowest'])
+        self.assertEqual(True, namespace.slowest)
+        namespace = os_testr.get_parser().parse_args(['--no-slowest'])
+        self.assertEqual(False, namespace.slowest)
+        self.assertRaises(SystemExit, os_testr.get_parser().parse_args,
+                          ['--no-slowest', '--slowest'])
+
+    def test_parallel(self):
+        namespace = os_testr.get_parser().parse_args(['--parallel'])
+        self.assertEqual(True, namespace.parallel)
+        namespace = os_testr.get_parser().parse_args(['--serial'])
+        self.assertEqual(False, namespace.parallel)
+        self.assertRaises(SystemExit, os_testr.get_parser().parse_args,
+                          ['--parallel', '--serial'])