Add support for selective test execution.

If there are any positional arguments to test/run-tests.py, they are matched
(verbatim, not as regular expressions) against each test's name.  Only those
tests whose names contain at least one of the positional arguments will be
run.  Thus, for instance, you can run just the webpage tests with

    ./test/run-tests.py module/webpage

or one specific test with

    ./test/run-tests.py exact/name/of/test.js

or the basics and standards tests with

    ./test/run-tests.py basics standards

If no tests at all match, run-tests.py will print "ALL TESTS SKIPPED" and
exit unsuccessfully.

Ongoing work on issue #12439.

test/run-tests.py

@@ -184,12 +184,14 @@ def init():
     www_path = os.path.join(base_path, 'www')
 
     parser = optparse.OptionParser(
-        usage='%prog [options]',
+        usage='%prog [options] [tests to run...]',
         description='Run PhantomJS tests.'
     )
     parser.add_option('--verbose', action='store_true', default=False, help='Show a verbose log')
     (options, args) = parser.parse_args(sys.argv[1:])
 
+    options.to_run = args
+
     if options.verbose:
         returncode, version = run_phantomjs('--version')
         print 'Checking PhantomJS version %s' % version
@@ -245,30 +247,45 @@ def run_test(script, name):
 def run_tests():
     setup_server()
     if not http_running:
-        return
+        return 1
 
     start = time.time()
     if options.verbose:
         print 'Starting the tests...'
-        print
 
     result = 0
+    any_executed = False
     for test_group in TESTS:
         test_group_name = os.path.dirname(test_group)
         test_glob = os.path.normpath(base_path + '/' + test_group)
 
         if options.verbose:
-            print 'Test group: %s...' % test_group_name
             print
+            print 'Test group: %s...' % test_group_name
 
         for test_script in glob.glob(test_glob):
             tname = test_group_name + '/' + os.path.basename(test_script)
+            if options.to_run:
+                for to_run in options.to_run:
+                    if to_run in tname:
+                        break
+                else:
+                    if options.verbose:
+                        print "%s: skipped" % tname
+                    continue
+
+            any_executed = True
             ret = run_test(test_script, tname)
             if ret != 0:
                 print 'The test %s FAILED' % tname
                 print
                 result = 1
 
+    if not any_executed:
+        result = 1
+        print
+        print 'ALL TESTS SKIPPED.'
+
     if result == 0:
         print
         print 'No failure. Finished in %d seconds.' % (time.time() - start)