testing: Conform runner to Django architecture.

In Django, TestSuite can contain objects of type TestSuite as well
along with TestCases. This is why the run method of TestSuite is
responsible for iterating over items of TestSuite.

This also gives us access to result object which is used by unittest
to gather information about testcases.

zerver/lib/test_runner.py

@@ -5,6 +5,7 @@ from typing import Any, Callable, Iterable, List, Optional, Set, Tuple
 from django.test import TestCase
 from django.test.runner import DiscoverRunner
 from django.test.signals import template_rendered
+from unittest import loader  # type: ignore  # Mypy cannot pick this up.
 
 from zerver.lib.cache import bounce_key_prefix_for_testing
 from zerver.lib.sqlalchemy_utils import get_sqlalchemy_connection
@@ -19,6 +20,9 @@ import time
 import traceback
 import unittest
 
+if False:
+    from unittest.result import TextTestResult
+
 def slow(slowness_reason):
     # type: (str) -> Callable[[Callable], Callable]
     '''
@@ -146,7 +150,28 @@ def run_test(test):
     test._post_teardown()
     return failed
 
+class TestSuite(unittest.TestSuite):
+    def run(self, result, debug=False):
+        # type: (TextTestResult, Optional[bool]) -> TextTestResult
+        for test in self:  # type: ignore  # Mypy cannot recognize this but this is correct. Taken from unittest.
+            result.startTest(test)
+            # The attributes __unittest_skip__ and __unittest_skip_why__ are undocumented
+            if hasattr(test, '__unittest_skip__') and test.__unittest_skip__:  # type: ignore
+                print('Skipping', full_test_name(test), "(%s)" % (test.__unittest_skip_why__,))  # type: ignore
+            elif run_test(test):
+                if result.failfast:
+                    break
+            result.stopTest(test)
+
+        return result
+
+class TestLoader(loader.TestLoader):
+    suiteClass = TestSuite
+
 class Runner(DiscoverRunner):
+    test_suite = TestSuite
+    test_loader = TestLoader()
+
     def __init__(self, *args, **kwargs):
         # type: (*Any, **Any) -> None
         DiscoverRunner.__init__(self, *args, **kwargs)
@@ -174,19 +199,6 @@ class Runner(DiscoverRunner):
         # type: () -> Set[str]
         return self.shallow_tested_templates
 
-    def run_suite(self, suite, **kwargs):
-        # type: (Iterable[TestCase], **Any) -> bool
-        failed = False
-        for test in suite:
-            # The attributes __unittest_skip__ and __unittest_skip_why__ are undocumented
-            if hasattr(test, '__unittest_skip__') and test.__unittest_skip__:
-                print('Skipping', full_test_name(test), "(%s)" % (test.__unittest_skip_why__,))
-            elif run_test(test):
-                failed = True
-                if self.failfast:
-                    return failed
-        return failed
-
     def run_tests(self, test_labels, extra_tests=None,
                   full_suite=False, **kwargs):
         # type: (List[str], Optional[List[TestCase]], bool, **Any) -> bool
@@ -207,8 +219,9 @@ class Runner(DiscoverRunner):
         # run a single test and getting an SA connection causes data from
         # a Django connection to be rolled back mid-test.
         get_sqlalchemy_connection()
-        failed = self.run_suite(suite)
+        result = self.run_suite(suite)
         self.teardown_test_environment()
+        failed = self.suite_result(suite, result)
         if not failed:
             write_instrumentation_reports(full_suite=full_suite)
         return failed