diff --git a/tests/base.py b/tests/base.py
index 2912337b2b..46c05b635e 100644
--- a/tests/base.py
+++ b/tests/base.py
@@ -2106,10 +2106,16 @@ class TestConfig:
     def __init__(self, testobj):
         test_name = testobj.id().split('.')[-1]
         test = getattr(testobj, test_name)
+        default_okay_tracebacks = [
+            # We log git merge errors at debug level with tracebacks;
+            # these are typically safe to ignore
+            'ERROR: content conflict',
+        ]
         self.simple_layout = getattr(test, '__simple_layout__', None)
         self.gerrit_config = getattr(test, '__gerrit_config__', {})
         self.never_capture = getattr(test, '__never_capture__', None)
-        self.okay_tracebacks = getattr(test, '__okay_tracebacks__', [])
+        self.okay_tracebacks = getattr(test, '__okay_tracebacks__',
+                                       default_okay_tracebacks)
         self.enable_nodepool = getattr(test, '__enable_nodepool__', False)
         self.return_data = getattr(test, '__return_data__', [])
         self.changes = FakeChangeDB()
diff --git a/tests/unit/test_executor.py b/tests/unit/test_executor.py
index 71974319bd..5d16d1dc2e 100644
--- a/tests/unit/test_executor.py
+++ b/tests/unit/test_executor.py
@@ -24,12 +24,13 @@ import time
 from unittest import mock
 
 from tests.base import (
-    BaseTestCase,
-    ZuulTestCase,
     AnsibleZuulTestCase,
+    BaseTestCase,
     FIXTURE_DIR,
+    ZuulTestCase,
+    iterate_timeout,
+    okay_tracebacks,
     simple_layout,
-    iterate_timeout
 )
 
 from zuul.executor.sensors.startingbuilds import StartingBuildsSensor
@@ -1258,6 +1259,7 @@ class TestExecutorFailure(ZuulTestCase):
     tenant_config_file = 'config/single-tenant/main.yaml'
 
     @mock.patch('zuul.executor.server.ExecutorServer.executeJob')
+    @okay_tracebacks('Failed to start')
     def test_executor_job_start_failure(self, execute_job_mock):
         execute_job_mock.side_effect = Exception('Failed to start')
         A = self.fake_gerrit.addFakeChange('org/project1', 'master', 'A')
@@ -1268,6 +1270,7 @@ class TestExecutorFailure(ZuulTestCase):
             '- project-merge .* ERROR',
             A.messages[-1]))
 
+    @okay_tracebacks("Transient error")
     def test_executor_transient_error(self):
         self.hold_jobs_in_queue = True
         A = self.fake_gerrit.addFakeChange('org/project1', 'master', 'A')
diff --git a/tests/unit/test_gerrit_awskinesis.py b/tests/unit/test_gerrit_awskinesis.py
index 8967f25518..7b56b008df 100644
--- a/tests/unit/test_gerrit_awskinesis.py
+++ b/tests/unit/test_gerrit_awskinesis.py
@@ -23,6 +23,7 @@ import tests.base
 from tests.base import (
     ZuulTestCase,
     iterate_timeout,
+    okay_tracebacks,
     simple_layout,
 )
 
@@ -110,6 +111,7 @@ class TestGerritEventSourceAWSKinesis(ZuulTestCase):
         self.assertEqual(B.reported, 1, "B should be reported")
 
     @simple_layout('layouts/simple.yaml')
+    @okay_tracebacks("invalid literal for int() with base 10: 'nope'")
     def test_kinesis_bad_checkpoint(self):
         listener = self.fake_gerrit.event_thread
 
diff --git a/tests/unit/test_gerrit_gcloud_pubsub.py b/tests/unit/test_gerrit_gcloud_pubsub.py
index cd069ad483..311daf1242 100644
--- a/tests/unit/test_gerrit_gcloud_pubsub.py
+++ b/tests/unit/test_gerrit_gcloud_pubsub.py
@@ -25,6 +25,7 @@ import tests.base
 from tests.base import (
     ZuulTestCase,
     iterate_timeout,
+    okay_tracebacks,
     simple_layout,
 )
 
@@ -120,6 +121,7 @@ class TestGerritEventSourceGcloudPubsub(ZuulTestCase):
         super().setUp()
 
     @simple_layout('layouts/simple.yaml')
+    @okay_tracebacks('Test error')
     def test_gcloud_pubsub(self):
         A = self.fake_gerrit.addFakeChange('org/project', 'master', 'A')
         subscriber = self.fake_gerrit.event_thread.subscriber
diff --git a/tests/unit/test_gerrit_kafka.py b/tests/unit/test_gerrit_kafka.py
index 6ee649b2e5..0fa642f775 100644
--- a/tests/unit/test_gerrit_kafka.py
+++ b/tests/unit/test_gerrit_kafka.py
@@ -24,6 +24,7 @@ import tests.base
 from tests.base import (
     ZuulTestCase,
     iterate_timeout,
+    okay_tracebacks,
     simple_layout,
 )
 
@@ -102,6 +103,7 @@ class TestGerritEventSourceKafka(ZuulTestCase):
         super().setUp()
 
     @simple_layout('layouts/simple.yaml')
+    @okay_tracebacks('Broker disconnected before response received')
     def test_kafka(self):
         A = self.fake_gerrit.addFakeChange('org/project', 'master', 'A')
         consumer = self.fake_gerrit.event_thread.consumer
diff --git a/tests/unit/test_github_driver.py b/tests/unit/test_github_driver.py
index 23d1e232a8..a51d4f7247 100644
--- a/tests/unit/test_github_driver.py
+++ b/tests/unit/test_github_driver.py
@@ -37,9 +37,15 @@ from zuul.model import MergeRequest, EnqueueEvent, DequeueEvent
 from zuul.zk.change_cache import ChangeKey
 
 from tests.util import random_sha1
-from tests.base import (AnsibleZuulTestCase, BaseTestCase,
-                        ZuulGithubAppTestCase, ZuulTestCase,
-                        simple_layout, iterate_timeout)
+from tests.base import (
+    AnsibleZuulTestCase,
+    BaseTestCase,
+    ZuulGithubAppTestCase,
+    ZuulTestCase,
+    iterate_timeout,
+    okay_tracebacks,
+    simple_layout,
+)
 from tests.base import ZuulWebFixture
 
 EMPTY_LAYOUT_STATE = LayoutState("", "", 0, None, {}, -1)
@@ -688,6 +694,8 @@ class TestGithubDriver(ZuulTestCase):
         self.assertIn(expected_warning, A.comments[1])
 
     @simple_layout('layouts/merging-github.yaml', driver='github')
+    @okay_tracebacks('Unknown merge failure',
+                     'Method not allowed')
     def test_report_pull_merge(self):
         # pipeline merges the pull request on success
         A = self.fake_github.openFakePullRequest('org/project', 'master',
@@ -1458,6 +1466,7 @@ class TestGithubDriver(ZuulTestCase):
         self.assertEqual(A.merge_message, pr_description)
 
     @simple_layout('layouts/basic-github.yaml', driver='github')
+    @okay_tracebacks('AttributeError')
     def test_invalid_event(self):
         # Regression test to make sure the event forwarder thread continues
         # running in case the event from the GithubEventProcessor is None.
@@ -2774,6 +2783,7 @@ class TestGithubDriverEnterpriseCache(ZuulGithubAppTestCase):
             git.refs.Reference.create(cache, ref, obj, force=True)
 
     @simple_layout('layouts/merging-github.yaml', driver='github')
+    @okay_tracebacks('find remote ref')
     def test_github_repo_cache(self):
         # Test that we fetch and configure retries correctly when
         # using a github enterprise repo cache (the cache can be
diff --git a/tests/unit/test_merger_repo.py b/tests/unit/test_merger_repo.py
index 2796d8c9d4..5897d6ee18 100644
--- a/tests/unit/test_merger_repo.py
+++ b/tests/unit/test_merger_repo.py
@@ -27,7 +27,12 @@ from zuul.merger.merger import MergerTree, Repo
 import zuul.model
 from zuul.model import MergeRequest
 from tests.base import (
-    BaseTestCase, ZuulTestCase, FIXTURE_DIR, simple_layout, iterate_timeout
+    BaseTestCase,
+    FIXTURE_DIR,
+    ZuulTestCase,
+    iterate_timeout,
+    okay_tracebacks,
+    simple_layout,
 )
 
 
@@ -289,6 +294,7 @@ class TestMergerRepo(ZuulTestCase):
         self.assertEqual(repo.remotes.origin.refs.missing.commit.hexsha,
                          commit_sha)
 
+    @okay_tracebacks('exit code')
     def test_clone_timeout(self):
         parent_path = os.path.join(self.upstream_root, 'org/project1')
         self.patch(git.Git, 'GIT_PYTHON_GIT_EXECUTABLE',
@@ -316,6 +322,7 @@ class TestMergerRepo(ZuulTestCase):
                                          r'.*exit code\(-9\)'):
             work_repo.update()
 
+    @okay_tracebacks('git_fetch_error.sh')
     def test_fetch_retry(self):
         parent_path = os.path.join(self.upstream_root, 'org/project1')
         self.patch(Repo, 'retry_interval', 1)
@@ -364,6 +371,7 @@ class TestMergerRepo(ZuulTestCase):
         # And now reset the repo. This should not crash
         work_repo.reset()
 
+    @okay_tracebacks('exit code')
     def test_broken_cache(self):
         parent_path = os.path.join(self.upstream_root, 'org/project1')
         work_repo = Repo(parent_path, self.workspace_root,
@@ -1339,6 +1347,7 @@ class TestMergerSchemes(ZuulTestCase):
         self._assertScheme(self.work_root, 'flat')
 
     @simple_layout('layouts/overlapping-repos.yaml')
+    @okay_tracebacks('collides with')
     def test_golang_collision(self):
         merger = self._getMerger(scheme=zuul.model.SCHEME_GOLANG)
         repo = merger.getRepo('gerrit', 'component')
@@ -1347,6 +1356,7 @@ class TestMergerSchemes(ZuulTestCase):
         self.assertIsNone(repo)
 
     @simple_layout('layouts/overlapping-repos.yaml')
+    @okay_tracebacks('collides with')
     def test_flat_collision(self):
         merger = self._getMerger(scheme=zuul.model.SCHEME_FLAT)
         repo = merger.getRepo('gerrit', 'component')
diff --git a/tests/unit/test_scheduler.py b/tests/unit/test_scheduler.py
index 1ae39fbda7..d5b751d0b1 100644
--- a/tests/unit/test_scheduler.py
+++ b/tests/unit/test_scheduler.py
@@ -41,14 +41,15 @@ import zuul.merger.merger
 from zuul.lib import yamlutil as yaml
 
 from tests.base import (
+    FIXTURE_DIR,
+    RecordingExecutorServer,
     SSLZuulTestCase,
+    TestConnectionRegistry,
     ZuulTestCase,
+    iterate_timeout,
+    okay_tracebacks,
     repack_repo,
     simple_layout,
-    iterate_timeout,
-    RecordingExecutorServer,
-    TestConnectionRegistry,
-    FIXTURE_DIR,
     skipIfMultiScheduler,
 )
 from zuul.zk.change_cache import ChangeKey
@@ -4815,6 +4816,7 @@ class TestScheduler(ZuulTestCase):
 
     @simple_layout('layouts/smtp.yaml')
     @mock.patch('zuul.driver.gerrit.gerritreporter.GerritReporter.report')
+    @okay_tracebacks('Gerrit failed to report')
     def test_failed_reporter(self, report_mock):
         '''Test that one failed reporter doesn't break other reporters'''
         # Warning hacks. We sort the reports here so that the test is
@@ -6568,6 +6570,7 @@ For CI problems and help debugging, contact ci@example.org"""
         self.assertTrue('YAY' in A.messages[0])
         self.assertTrue('BOO' in A.messages[0])
 
+    @okay_tracebacks('git_fail.sh')
     def test_merge_error(self):
         # Test we don't get stuck on a merger error
         self.waitUntilSettled()
diff --git a/tests/unit/test_sos.py b/tests/unit/test_sos.py
index dd7818686f..eca6bdc715 100644
--- a/tests/unit/test_sos.py
+++ b/tests/unit/test_sos.py
@@ -19,7 +19,12 @@ from unittest import mock
 
 import zuul.model
 
-from tests.base import iterate_timeout, ZuulTestCase, simple_layout
+from tests.base import (
+    ZuulTestCase,
+    iterate_timeout,
+    okay_tracebacks,
+    simple_layout,
+)
 from zuul.zk.locks import SessionAwareWriteLock, TENANT_LOCK_ROOT
 from zuul.scheduler import PendingReconfiguration
 
@@ -456,6 +461,7 @@ class TestScaleOutScheduler(ZuulTestCase):
             dict(name='project-test2', result='SUCCESS', changes='1,1 2,1'),
         ], ordered=False)
 
+    @okay_tracebacks('Unterminated string starting at')
     def test_pipeline_summary(self):
         # Test that we can deal with a truncated pipeline summary
         self.executor_server.hold_jobs_in_build = True
diff --git a/tests/unit/test_v3.py b/tests/unit/test_v3.py
index c23f4affcb..0ecd98c2db 100644
--- a/tests/unit/test_v3.py
+++ b/tests/unit/test_v3.py
@@ -36,10 +36,10 @@ from zuul.zk.blob_store import BlobStore
 
 from tests.base import (
     AnsibleZuulTestCase,
-    ZuulTestCase,
     FIXTURE_DIR,
-    simple_layout,
+    ZuulTestCase,
     iterate_timeout,
+    simple_layout,
     skipIfMultiScheduler,
 )
 from tests.util import random_sha1