Issue #15302: Switch regrtest from using getopt to using argparse.

This is the first step in refactoring regrtest to use argparse.  The
regrtest module's main() function still expects a getopt-style return
value rather than an argparse.Namespace instance.

Lib/test/test_regrtest.py

@@ -0,0 +1,96 @@
+"""
+Tests of regrtest.py.
+"""
+
+import argparse
+import getopt
+import unittest
+from test import regrtest, support
+
+def old_parse_args(args):
+    """Parse arguments as regrtest did strictly prior to 3.4.
+
+    Raises getopt.GetoptError on bad arguments.
+    """
+    return getopt.getopt(args, 'hvqxsoS:rf:lu:t:TD:NLR:FdwWM:nj:Gm:',
+        ['help', 'verbose', 'verbose2', 'verbose3', 'quiet',
+         'exclude', 'single', 'slow', 'randomize', 'fromfile=', 'findleaks',
+         'use=', 'threshold=', 'coverdir=', 'nocoverdir',
+         'runleaks', 'huntrleaks=', 'memlimit=', 'randseed=',
+         'multiprocess=', 'coverage', 'slaveargs=', 'forever', 'debug',
+         'start=', 'nowindows', 'header', 'testdir=', 'timeout=', 'wait',
+         'failfast', 'match='])
+
+class ParseArgsTestCase(unittest.TestCase):
+
+    """Test that regrtest._parse_args() matches the prior getopt behavior."""
+
+    def _parse_args(self, args):
+        return regrtest._parse_args(args=args)
+
+    def _check_args(self, args, expected=None):
+        """
+        The expected parameter is for cases when the behavior of the new
+        parse_args differs from the old (but deliberately so).
+        """
+        if expected is None:
+            try:
+                expected = old_parse_args(args)
+            except getopt.GetoptError:
+                # Suppress usage string output when an argparse.ArgumentError
+                # error is raised.
+                with support.captured_stderr():
+                    self.assertRaises(SystemExit, self._parse_args, args)
+                return
+        # The new parse_args() sorts by long option string.
+        expected[0].sort()
+        actual = self._parse_args(args)
+        self.assertEqual(actual, expected)
+
+    def test_unrecognized_argument(self):
+        self._check_args(['--xxx'])
+
+    def test_value_not_provided(self):
+        self._check_args(['--start'])
+
+    def test_short_option(self):
+        # getopt returns the short option whereas argparse returns the long.
+        expected = ([('--quiet', '')], [])
+        self._check_args(['-q'], expected=expected)
+
+    def test_long_option(self):
+        self._check_args(['--quiet'])
+
+    def test_long_option__partial(self):
+        self._check_args(['--qui'])
+
+    def test_two_options(self):
+        self._check_args(['--quiet', '--exclude'])
+
+    def test_option_with_value(self):
+        self._check_args(['--start', 'foo'])
+
+    def test_option_with_empty_string_value(self):
+        self._check_args(['--start', ''])
+
+    def test_arg(self):
+        self._check_args(['foo'])
+
+    def test_option_and_arg(self):
+        self._check_args(['--quiet', 'foo'])
+
+    def test_fromfile(self):
+        self._check_args(['--fromfile', 'file'])
+
+    def test_match(self):
+        self._check_args(['--match', 'pattern'])
+
+    def test_randomize(self):
+        self._check_args(['--randomize'])
+
+
+def test_main():
+    support.run_unittest(__name__)
+
+if __name__ == '__main__':
+    test_main()