test-bots: Load and discover unit tests from specific modules.

Instead of discovering unit tests using loader.discover() by passing
it a set of starting and top level directories, we now discover
unit tests by loading them from specific test module objects. This
makes it easier to include and exclude specific bots from testing.

tools/test-bots

@@ -1,72 +1,80 @@
 #!/usr/bin/env python
 
-from __future__ import absolute_import
-from __future__ import print_function
-
+from os.path import dirname, basename
+from importlib import import_module
 import argparse
 import os
-import sys
+import glob
 import unittest
 import logging
-from unittest import TestCase
 
-def dir_join(dir1, dir2):
-    # type: (str, str) -> str
-    return os.path.abspath(os.path.join(dir1, dir2))
+
+def load_tests_from_modules(names, template):
+    loader = unittest.defaultTestLoader
+    test_suites = []
+
+    for name in names:
+        module = import_module(template.format(name=name))
+        test_suites.append(loader.loadTestsFromModule(module))
+
+    return test_suites
+
+
+def parse_args(available_bots):
+    description = """
+Script to run test_<bot_name>.py files in the
+zulip_bot/zulip_bots/bots/<bot_name> directories.
+
+Running tests for all bots:
+
+./test-bots
+
+Running tests for specific bots:
+
+./test-bots define thesaurus
+
+Running tests for all bots excluding certain bots (the
+following command would run tests for all bots except
+the tests for xkcd and wikipedia bots):
+
+./test-bots --exclude xkcd wikipedia
+"""
+    parser = argparse.ArgumentParser(description=description)
+
+    parser.add_argument('bots_to_test',
+                        metavar='bot',
+                        nargs='*',
+                        default=available_bots,
+                        help='specific bots to test (default is all)')
+
+    parser.add_argument('--exclude',
+                        metavar='bot',
+                        nargs='*',
+                        default=[],
+                        help='bot(s) to exclude')
+    return parser.parse_args()
+
+
+def main():
+    glob_pattern = os.path.abspath('../zulip_bots/zulip_bots/bots/*/test_*.py')
+    test_modules = glob.glob(glob_pattern)
+
+    # get only the names of bots that have tests
+    available_bots = map(lambda path: basename(dirname(path)), test_modules)
+
+    options = parse_args(available_bots)
+
+    bots_to_test = filter(lambda bot: bot not in options.exclude,
+                          options.bots_to_test)
+    test_suites = load_tests_from_modules(
+        bots_to_test,
+        template='zulip_bots.bots.{name}.test_{name}'
+    )
+
+    suite = unittest.TestSuite(test_suites)
+    runner = unittest.TextTestRunner(verbosity=2)
+    runner.run(suite)
 
 
 if __name__ == '__main__':
-
-    tools_dir = os.path.dirname(os.path.abspath(__file__))
-    bots_dir = os.path.join(tools_dir, '..', 'zulip_bots', 'zulip_bots')
-    bots_test_dir = dir_join(bots_dir, 'bots')
-
-    sys.path.insert(0, bots_dir)
-    sys.path.insert(0, bots_test_dir)
-
-    btd = bots_test_dir
-    available_bots = [b for b in os.listdir(btd) if os.path.isdir(dir_join(btd, b))]
-
-    description = 'Script to run test_<bot>.py files in api/bots/<bot> directories'
-    parser = argparse.ArgumentParser(description=description)
-    parser.add_argument('bots_to_test', metavar='bot', nargs='*', default=available_bots,
-                        help='specific bots to test (default is all)')
-    parser.add_argument('--exclude', metavar='bot', action='append', default=[],
-                        help='specific bot to exclude (can be used multiple times)')
-    args = parser.parse_args()
-
-    failed = False
-    if args.bots_to_test != available_bots and len(args.bots_to_test) > 0:
-        for n in args.bots_to_test:
-            if n not in available_bots:
-                logging.warning("Bot with name '%s' is unavailable for testing." % (n))
-                args.bots_to_test.remove(n)
-                failed = True
-
-    for to_exclude in args.exclude:
-        if to_exclude in args.bots_to_test:
-            args.bots_to_test.remove(to_exclude)
-
-    # mypy doesn't recognize the TestLoader attribute, even though the code
-    # is executable
-    loader = unittest.TestLoader()  # type: ignore
-
-    suites = []
-    for bot_to_test in args.bots_to_test:
-        dep_path = os.path.join(bots_test_dir, bot_to_test, 'bot_dependencies')
-        sys.path.insert(0, dep_path)
-        try:
-            suites.append(loader.discover(start_dir = dir_join(bots_test_dir, bot_to_test),
-                                          top_level_dir = bots_dir))
-        except ImportError:
-            logging.error("Bot %s requires __init__.py to be added" % (bot_to_test))
-            failed = True
-
-    suite = unittest.TestSuite(suites)
-    runner = unittest.TextTestRunner(verbosity=2)
-    # same issue as for TestLoader
-    result = runner.run(suite)  # type: ignore
-    if result.errors or result.failures:
-        raise Exception('Test failed!')
-
-    sys.exit(failed)
+    main()