racetest: Mark check_race_external_invalidate_vs_disconnect as long-running

And add a way to run tests without long tests:

	zope-testrunner --at-level=1

will run tests without those marked as being long.

By default tox continues to run all tests.

Suggested by @d-maurer with the idea to be able to skip long tests that
are unlikely to fail during development:

https://github.com/zopefoundation/ZODB/pull/368#discussion_r946386969

.meta.toml

@@ -14,6 +14,9 @@ with-sphinx-doctests = false
 
 [tox]
 use-flake8 = true
+testenv-commands = [
+    "zope-testrunner --test-path=src --all {posargs:-vc}",
+    ]
 testenv-setenv = [
     "ZOPE_INTERFACE_STRICT_IRO=1",
     ]

src/ZODB/tests/racetest.py

@@ -45,7 +45,7 @@ import transaction
 from ZODB import DB, POSException
 from ZODB.utils import tid_repr, at2before
 from ZODB.tests.MinPO import MinPO
-from ZODB.tests.util import with_high_concurrency
+from ZODB.tests.util import with_high_concurrency, long_test
 
 import threading
 from random import randint
@@ -352,6 +352,7 @@ class RaceTests(object):
     # state, or in new state after the next transaction. Contrary to that, with
     # T2ObjectsInc2Phase the invariant will be detected to be broken on the
     # next transaction.
+    @long_test
     def check_race_external_invalidate_vs_disconnect(self):
         return self._check_race_xxx_vs_external_disconnect(
                                                 T2ObjectsInc2Phase())

src/ZODB/tests/util.py

@@ -113,6 +113,23 @@ class TestCase(unittest.TestCase):
 
     tearDown = tearDown
 
+    # propagate .level from tested method to TestCase so that e.g. @long_test
+    # works
+    @property
+    def level(self):
+        f = getattr(self, self._testMethodName)
+        return getattr(f, 'level', 1)
+
+
+def long_test(f):
+    """
+    long_test decorates f to be marked as long-running test.
+
+    Use `zope-testrunner --at-level=1` to run tests without the long-ones.
+    """
+    f.level = 2
+    return f
+
 
 def pack(db):
     db.pack(time.time()+1)

tox.ini

@@ -23,7 +23,7 @@ deps =
 setenv =
     ZOPE_INTERFACE_STRICT_IRO=1
 commands =
-    zope-testrunner --test-path=src {posargs:-vc}
+    zope-testrunner --test-path=src --all {posargs:-vc}
 extras =
     test