add TestGroup tests; minor cleanup

src/ZODB/tests/racetest.py

@@ -200,7 +200,7 @@ def xrun(tg, tx, f, N):
             for i in range(N):
                 # print('%s.%d' % (f.__name__, i))
                 f(tg)
-                if tg.failed.is_set():
+                if tg.failed():
                     break
 
         # loop verify and modify concurrently.
@@ -308,7 +308,7 @@ def t_():
                 for i in range(N):
                     # print('T%s.%d' % (tx, i))
                     t_()
-                    if tg.failed.is_set():
+                    if tg.failed():
                         break
             finally:
                 db.close()
@@ -392,15 +392,15 @@ def work1(db):
                 db = self.dbopen()
                 try:
                     for i in range(4):
-                        if tg.failed.is_set():
+                        if tg.failed():
                             break
                         work1(db)
                 finally:
                     db.close()
 
             for i in range(N):
                 # print('T%s.%d' % (tx, i))
-                if tg.failed.is_set():
+                if tg.failed():
                     break
                 t_()
 
@@ -490,12 +490,13 @@ class TestGroup(object):
        - .go() adds test thread to the group.
        - .wait() waits for all spawned threads to finish and reports all
          collected failures to containing testcase.
-       - a test should indicate failure by call to .fail()
+       - a test should indicate failure by call to .fail(), it
+         can check for a failure with .failed()
     """
 
     def __init__(self, testcase):
         self.testcase = testcase
-        self.failed = threading.Event()
+        self.failed_event = threading.Event()
         self.fail_mu = threading.Lock()
         self.failv = []           # failures registerd by .fail
         self.threadv = []         # spawned threads
@@ -505,7 +506,11 @@ def fail(self, msg):
         """fail adds failure to test result."""
         with self.fail_mu:
             self.failv.append(msg)
-        self.failed.set()
+        self.failed_event.set()
+
+    def failed(self):
+        """did the thest already fail."""
+        return self.failed_event.is_set()
 
     def go(self, f, *argv, **kw):
         """go spawns f(self, #thread, *argv, **kw) in new test thread."""
@@ -517,11 +522,12 @@ def go(self, f, *argv, **kw):
         t.start()
 
     def _run(self, f, tx, argv, kw):
+        tname = self.threadv[tx].name
         try:
             f(self, tx, *argv, **kw)
         except Exception as e:
             self.fail("Unhandled exception %r in thread %s"
-                      % (e, self.threadv[tx].name))
+                      % (e, tname))
             raise
         finally:
             self.waitg.done()
@@ -537,13 +543,14 @@ def wait(self, timeout):
             try:
                 t.join(1)
             except AssertionError:
-                self.failed.set()
+                self.failed_event.set()
                 failed_to_finish.append(t.name)
         if failed_to_finish:
             self.fail("threads did not finish: %s" % failed_to_finish)
+        del self.threadv  # avoid cyclic garbage
 
-        if self.failed.is_set():
-            self.testcase.fail('\n\n'.join([_ for _ in self.failv if _]))
+        if self.failed():
+            self.testcase.fail('\n\n'.join(self.failv))
 
 
 class Daemon(threading.Thread):
@@ -616,7 +623,7 @@ def add(self, delta):
             if self.n < 0:
                 raise AssertionError("#workers is negative")
             if self.n == 0:
-                self.condition.notify()
+                self.condition.notify_all()
 
     def done(self):
         self.add(-1)