diff --git a/tests/gold_tests/autest-site/trafficserver.test.ext b/tests/gold_tests/autest-site/trafficserver.test.ext
index a6881f056a7..fc0acd90b30 100755
--- a/tests/gold_tests/autest-site/trafficserver.test.ext
+++ b/tests/gold_tests/autest-site/trafficserver.test.ext
@@ -40,7 +40,8 @@ default_log_data = {
 
 def MakeATSProcess(obj, name, command='traffic_server', select_ports=True,
                    enable_tls=False, enable_cache=True, enable_quic=False,
-                   block_for_debug=False, log_data=default_log_data):
+                   block_for_debug=False, log_data=default_log_data,
+                   use_traffic_out=True):
     #####################################
     # common locations
 
@@ -71,13 +72,28 @@ def MakeATSProcess(obj, name, command='traffic_server', select_ports=True,
     storage_dir = os.path.join(ts_dir, 'storage')
     cache_dir = os.path.join(ts_dir, 'cache')
 
+    ts_args = ''
+    if use_traffic_out:
+        # Bind stdout/err to traffic.out. This allows tests to wait upon
+        # content from the traffic.out file, something that cannot be done on
+        # process stdout/stderr in AuTest.
+        traffic_out = os.path.join(log_dir, 'traffic.out')
+        ts_args += f' --bind_stderr {traffic_out}'
+        ts_args += f' --bind_stdout {traffic_out}'
+
     if block_for_debug:
-        if command.startswith('traffic_server'):
-            command += ' --block'
-        elif command.startswith('traffic_manager'):
-            if '--tsArgs' not in command:
-                command += ' --tsArgs'
-            command += ' --block'
+        ts_args += ' --block'
+
+    if 'traffic_manager' in command:
+        if '--tsArgs' in command:
+            # None of our tests do this, but if we eventually pass in --tsArgs
+            # at some point from a test, we'll need to figure out how to mix
+            # that with the arguments we're assembling for --tsArgs here.
+            host.WriteError('Do not know how to assemble --tsArgs.')
+        if ts_args:
+            command += f' --tsArgs "{ts_args}"'
+    elif 'traffic_server' in command:
+        command += ts_args
 
     # create process
     p = obj.Processes.Process(name, command)
@@ -220,7 +236,12 @@ def MakeATSProcess(obj, name, command='traffic_server', select_ports=True,
         "Unrecognized configuration value",
         f"Diags log file {fname} should not contain a warning about an unrecognized configuration")
 
-    if command == "traffic_manager":
+    # traffic.out
+    fname = "traffic.out"
+    tmpname = os.path.join(log_dir, fname)
+    p.Disk.File(tmpname, id='traffic_out')
+
+    if "traffic_manager" in command:
         fname = log_data['manager']
         if fname == 'stdout':
             p.Disk.manager_log = p.Streams.stdout
@@ -364,7 +385,7 @@ def MakeATSProcess(obj, name, command='traffic_server', select_ports=True,
     p.Env['PROXY_CONFIG_ADMIN_AUTOCONF_PORT'] = str(
         p.Variables.admin_port)  # support pre ATS 6.x
 
-    if command == "traffic_manager":
+    if 'traffic_manager' in command:
         p.ReturnCode = 2
     else:
         p.ReturnCode = 0
diff --git a/tests/gold_tests/chunked_encoding/bad_chunked_encoding.test.py b/tests/gold_tests/chunked_encoding/bad_chunked_encoding.test.py
index f5c3002d042..ac4709186e8 100644
--- a/tests/gold_tests/chunked_encoding/bad_chunked_encoding.test.py
+++ b/tests/gold_tests/chunked_encoding/bad_chunked_encoding.test.py
@@ -160,7 +160,7 @@ def setupTS(self):
         self.ts.Disk.remap_config.AddLine(
             f"map / http://127.0.0.1:{self.server.Variables.http_port}/",
         )
-        self.ts.Streams.stderr += Testers.ContainsExpression(
+        self.ts.Disk.traffic_out.Content += Testers.ContainsExpression(
             "user agent post chunk decoding error",
             "Verify that ATS detected a problem parsing a chunk.")
 
diff --git a/tests/gold_tests/cont_schedule/schedule.test.py b/tests/gold_tests/cont_schedule/schedule.test.py
index d5e58ecafad..53a25995baa 100644
--- a/tests/gold_tests/cont_schedule/schedule.test.py
+++ b/tests/gold_tests/cont_schedule/schedule.test.py
@@ -45,5 +45,5 @@
 tr.Processes.Default.Command = 'printf "Test TSContSchedule API"'
 tr.Processes.Default.ReturnCode = 0
 tr.Processes.Default.StartBefore(ts)
-ts.Streams.All = "gold/schedule.gold"
-ts.Streams.All += Testers.ExcludesExpression('fail', 'should not contain "fail"')
+ts.Disk.traffic_out.Content = "gold/schedule.gold"
+ts.Disk.traffic_out.Content += Testers.ExcludesExpression('fail', 'should not contain "fail"')
diff --git a/tests/gold_tests/cont_schedule/schedule_on_pool.test.py b/tests/gold_tests/cont_schedule/schedule_on_pool.test.py
index 176478c6e77..633970cc360 100644
--- a/tests/gold_tests/cont_schedule/schedule_on_pool.test.py
+++ b/tests/gold_tests/cont_schedule/schedule_on_pool.test.py
@@ -45,5 +45,5 @@
 tr.Processes.Default.Command = 'printf "Test TSContScheduleOnPool API"'
 tr.Processes.Default.ReturnCode = 0
 tr.Processes.Default.StartBefore(ts)
-ts.Streams.All = "gold/schedule_on_pool.gold"
-ts.Streams.All += Testers.ExcludesExpression('fail', 'should not contain "fail"')
+ts.Disk.traffic_out.Content = "gold/schedule_on_pool.gold"
+ts.Disk.traffic_out.Content += Testers.ExcludesExpression('fail', 'should not contain "fail"')
diff --git a/tests/gold_tests/cont_schedule/schedule_on_thread.test.py b/tests/gold_tests/cont_schedule/schedule_on_thread.test.py
index f54dbe2c78d..10e99af1522 100644
--- a/tests/gold_tests/cont_schedule/schedule_on_thread.test.py
+++ b/tests/gold_tests/cont_schedule/schedule_on_thread.test.py
@@ -45,5 +45,5 @@
 tr.Processes.Default.Command = 'printf "Test TSContScheduleOnThread API"'
 tr.Processes.Default.ReturnCode = 0
 tr.Processes.Default.StartBefore(ts)
-ts.Streams.All = "gold/schedule_on_thread.gold"
-ts.Streams.All += Testers.ExcludesExpression('fail', 'should not contain "fail"')
+ts.Disk.traffic_out.Content = "gold/schedule_on_thread.gold"
+ts.Disk.traffic_out.Content += Testers.ExcludesExpression('fail', 'should not contain "fail"')
diff --git a/tests/gold_tests/cont_schedule/thread_affinity.test.py b/tests/gold_tests/cont_schedule/thread_affinity.test.py
index 3562eb46b03..3ac4e632674 100644
--- a/tests/gold_tests/cont_schedule/thread_affinity.test.py
+++ b/tests/gold_tests/cont_schedule/thread_affinity.test.py
@@ -45,5 +45,5 @@
 tr.Processes.Default.Command = 'printf "Test TSContThreadAffinity API"'
 tr.Processes.Default.ReturnCode = 0
 tr.Processes.Default.StartBefore(ts)
-ts.Streams.All = "gold/thread_affinity.gold"
-ts.Streams.All += Testers.ExcludesExpression('fail', 'should not contain "fail"')
+ts.Disk.traffic_out.Content = "gold/thread_affinity.gold"
+ts.Disk.traffic_out.Content += Testers.ExcludesExpression('fail', 'should not contain "fail"')
diff --git a/tests/gold_tests/continuations/session_id.test.py b/tests/gold_tests/continuations/session_id.test.py
index 9e8f90d761d..2114898e905 100644
--- a/tests/gold_tests/continuations/session_id.test.py
+++ b/tests/gold_tests/continuations/session_id.test.py
@@ -106,4 +106,4 @@ def verify_session_count(output):
     return ""
 
 
-ts.Streams.All += Testers.FileContentCallback(verify_session_count, 'verify_session_count')
+ts.Disk.traffic_out.Content += Testers.FileContentCallback(verify_session_count, 'verify_session_count')
diff --git a/tests/gold_tests/h2/nghttp.test.py b/tests/gold_tests/h2/nghttp.test.py
index 8cc94f749f2..d43581e6dce 100644
--- a/tests/gold_tests/h2/nghttp.test.py
+++ b/tests/gold_tests/h2/nghttp.test.py
@@ -90,4 +90,4 @@
 tr.StillRunningAfter = httpbin
 tr.StillRunningAfter = ts
 
-ts.Streams.stderr = "gold/nghttp_ts_stderr.gold"
+ts.Disk.traffic_out.Content = "gold/nghttp_ts_stderr.gold"
diff --git a/tests/gold_tests/ip_allow/ip_allow.test.py b/tests/gold_tests/ip_allow/ip_allow.test.py
index 5eb79396ccd..8ec30000c6a 100644
--- a/tests/gold_tests/ip_allow/ip_allow.test.py
+++ b/tests/gold_tests/ip_allow/ip_allow.test.py
@@ -131,10 +131,10 @@
 '''.split("\n")
 )
 
-ts.Streams.stderr += Testers.ContainsExpression(
+ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Line 1 denial for 'CONNECT' from 127.0.0.1",
     "The CONNECT request should be denied by ip_allow")
-ts.Streams.stderr += Testers.ContainsExpression(
+ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Line 1 denial for 'PUSH' from 127.0.0.1",
     "The PUSH request should be denied by ip_allow")
 
diff --git a/tests/gold_tests/logging/log-debug-client-ip.test.py b/tests/gold_tests/logging/log-debug-client-ip.test.py
index 705ed4920ce..53efbcd6872 100644
--- a/tests/gold_tests/logging/log-debug-client-ip.test.py
+++ b/tests/gold_tests/logging/log-debug-client-ip.test.py
@@ -37,16 +37,16 @@
 
 # Verify that the various aspects of the expected debug output for the
 # transaction are logged.
-ts.Streams.stderr = Testers.ContainsExpression(
+ts.Disk.traffic_out.Content = Testers.ContainsExpression(
     r"\+ Incoming Request \+",
     "Make sure the client request information is present.")
-ts.Streams.stderr += Testers.ContainsExpression(
+ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     r"\+ Proxy's Request after hooks \+",
     "Make sure the proxy request information is present.")
-ts.Streams.stderr += Testers.ContainsExpression(
+ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     r"\+ Incoming O.S. Response \+",
     "Make sure the server's response information is present.")
-ts.Streams.stderr += Testers.ContainsExpression(
+ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     r"\+ Proxy's Response 2 \+",
     "Make sure the proxy response information is present.")
 
diff --git a/tests/gold_tests/logging/log-filenames.test.py b/tests/gold_tests/logging/log-filenames.test.py
index 6744a8c0730..5f94f3236df 100644
--- a/tests/gold_tests/logging/log-filenames.test.py
+++ b/tests/gold_tests/logging/log-filenames.test.py
@@ -67,7 +67,7 @@ def __configure_traffic_manager(self, log_data):
         self._ts_name = f"ts{LogFilenamesTest.__ts_counter}"
         LogFilenamesTest.__ts_counter += 1
         self.ts = Test.MakeATSProcess(self._ts_name, command="traffic_manager",
-                                      log_data=log_data)
+                                      use_traffic_out=False, log_data=log_data)
         self.ts.Disk.records_config.update({
             'proxy.config.diags.debug.enabled': 0,
             'proxy.config.diags.debug.tags': 'log',
diff --git a/tests/gold_tests/logging/log_pipe.test.py b/tests/gold_tests/logging/log_pipe.test.py
index 7488c4031ea..0d6961ffb09 100644
--- a/tests/gold_tests/logging/log_pipe.test.py
+++ b/tests/gold_tests/logging/log_pipe.test.py
@@ -75,15 +75,15 @@ def get_ts(logging_config):
 
 pipe_path = os.path.join(ts.Variables.LOGDIR, pipe_name)
 
-ts.Streams.All += Testers.ContainsExpression(
+ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Created named pipe .*{}".format(pipe_name),
     "Verify that the named pipe was created")
 
-ts.Streams.All += Testers.ContainsExpression(
+ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "no readers for pipe .*{}".format(pipe_name),
     "Verify that no readers for the pipe was detected.")
 
-ts.Streams.All += Testers.ExcludesExpression(
+ts.Disk.traffic_out.Content += Testers.ExcludesExpression(
     "New buffer size for pipe".format(pipe_name),
     "Verify that the default pipe size was used.")
 
@@ -136,15 +136,15 @@ def get_ts(logging_config):
 
 pipe_path = os.path.join(ts.Variables.LOGDIR, pipe_name)
 
-ts.Streams.All += Testers.ContainsExpression(
+ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Created named pipe .*{}".format(pipe_name),
     "Verify that the named pipe was created")
 
-ts.Streams.All += Testers.ContainsExpression(
+ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "no readers for pipe .*{}".format(pipe_name),
     "Verify that no readers for the pipe was detected.")
 
-ts.Streams.All += Testers.ContainsExpression(
+ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Previous buffer size for pipe .*{}".format(pipe_name),
     "Verify that the named pipe's size was adjusted")
 
@@ -156,7 +156,7 @@ def get_ts(logging_config):
 # requested, but it should be at least that big. We use the
 # pipe_buffer_is_larger_than.py helper script to verify that the pipe grew in
 # size.
-ts.Streams.All += Testers.ContainsExpression(
+ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "New buffer size for pipe.*{}".format(pipe_name),
     "Verify that the named pipe's size was adjusted")
 buffer_verifier = "pipe_buffer_is_larger_than.py"
diff --git a/tests/gold_tests/logging/log_retention.test.py b/tests/gold_tests/logging/log_retention.test.py
index 605bfd84a26..453155653c9 100644
--- a/tests/gold_tests/logging/log_retention.test.py
+++ b/tests/gold_tests/logging/log_retention.test.py
@@ -174,23 +174,23 @@ def get_command_to_rotate_thrice(self):
 )
 
 # Verify that each log type was registered for auto-deletion.
-test.ts.Streams.stderr = Testers.ContainsExpression(
+test.ts.Disk.traffic_out.Content = Testers.ContainsExpression(
     "Registering rotated log deletion for test_deletion.log with min roll count 0",
     "Verify test_deletion.log auto-delete configuration")
-test.ts.Streams.stderr += Testers.ContainsExpression(
+test.ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Registering rotated log deletion for error.log with min roll count 0",
     "Verify error.log auto-delete configuration")
-test.ts.Streams.stderr += Testers.ContainsExpression(
+test.ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Registering rotated log deletion for traffic.out with min roll count 0",
     "Verify traffic.out auto-delete configuration")
-test.ts.Streams.stderr += Testers.ContainsExpression(
+test.ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Registering rotated log deletion for diags.log with min roll count 0",
     "Verify diags.log auto-delete configuration")
-test.ts.Streams.stderr += Testers.ContainsExpression(
+test.ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Registering rotated log deletion for manager.log with min roll count 0",
     "Verify manager.log auto-delete configuration")
 # Verify test_deletion was rotated and deleted.
-test.ts.Streams.stderr += Testers.ContainsExpression(
+test.ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     f"The rolled logfile.*test_deletion.log_{specified_hostname}.*was auto-deleted.*bytes were reclaimed",
     "Verify that space was reclaimed")
 
@@ -222,24 +222,24 @@ def get_command_to_rotate_thrice(self):
 )
 
 # Verify that each log type was registered for auto-deletion.
-test.ts.Streams.stderr = Testers.ContainsExpression(
+test.ts.Disk.traffic_out.Content = Testers.ContainsExpression(
     "Registering rotated log deletion for test_deletion.log with min roll count 1",
     "Verify test_deletion.log auto-delete configuration")
 # Only the test_deletion should have its min_count overridden.
-test.ts.Streams.stderr += Testers.ContainsExpression(
+test.ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Registering rotated log deletion for error.log with min roll count 0",
     "Verify error.log auto-delete configuration")
-test.ts.Streams.stderr += Testers.ContainsExpression(
+test.ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Registering rotated log deletion for traffic.out with min roll count 0",
     "Verify traffic.out auto-delete configuration")
-test.ts.Streams.stderr += Testers.ContainsExpression(
+test.ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Registering rotated log deletion for diags.log with min roll count 0",
     "Verify diags.log auto-delete configuration")
-test.ts.Streams.stderr += Testers.ContainsExpression(
+test.ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Registering rotated log deletion for manager.log with min roll count 0",
     "Verify manager.log auto-delete configuration")
 # Verify test_deletion was rotated and deleted.
-test.ts.Streams.stderr += Testers.ContainsExpression(
+test.ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     f"The rolled logfile.*test_deletion.log_{specified_hostname}.*was auto-deleted.*bytes were reclaimed",
     "Verify that space was reclaimed")
 
@@ -257,23 +257,23 @@ def get_command_to_rotate_thrice(self):
 Test.PrepareTestPlugin(os.path.join(Test.Variables.AtsTestPluginsDir, 'test_log_interface.so'), test.ts)
 
 # Verify that the plugin's logs and other core logs were registered for deletion.
-test.ts.Streams.stderr = Testers.ContainsExpression(
+test.ts.Disk.traffic_out.Content = Testers.ContainsExpression(
     "Registering rotated log deletion for test_log_interface.log with min roll count 0",
     "Verify test_log_interface.log auto-delete configuration")
-test.ts.Streams.stderr += Testers.ContainsExpression(
+test.ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Registering rotated log deletion for error.log with min roll count 0",
     "Verify error.log auto-delete configuration")
-test.ts.Streams.stderr += Testers.ContainsExpression(
+test.ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Registering rotated log deletion for traffic.out with min roll count 0",
     "Verify traffic.out auto-delete configuration")
-test.ts.Streams.stderr += Testers.ContainsExpression(
+test.ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Registering rotated log deletion for diags.log with min roll count 0",
     "Verify diags.log auto-delete configuration")
-test.ts.Streams.stderr += Testers.ContainsExpression(
+test.ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Registering rotated log deletion for manager.log with min roll count 0",
     "Verify manager.log auto-delete configuration")
 # Verify test_deletion was rotated and deleted.
-test.ts.Streams.stderr += Testers.ContainsExpression(
+test.ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "The rolled logfile.*test_log_interface.log_.*was auto-deleted.*bytes were reclaimed",
     "Verify that space was reclaimed")
 
@@ -313,34 +313,34 @@ def get_command_to_rotate_thrice(self):
 )
 
 # Verify that each log type was registered for auto-deletion.
-test.ts.Streams.stderr = Testers.ContainsExpression(
+test.ts.Disk.traffic_out.Content = Testers.ContainsExpression(
     "Registering rotated log deletion for test_low_priority_deletion.log with min roll count 5",
     "Verify test_low_priority_deletion.log auto-delete configuration")
-test.ts.Streams.stderr += Testers.ContainsExpression(
+test.ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Registering rotated log deletion for test_high_priority_deletion.log with min roll count 1",
     "Verify test_high_priority_deletion.log auto-delete configuration")
 # Only the test_deletion should have its min_count overridden.
-test.ts.Streams.stderr += Testers.ContainsExpression(
+test.ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Registering rotated log deletion for error.log with min roll count 0",
     "Verify error.log auto-delete configuration")
-test.ts.Streams.stderr += Testers.ContainsExpression(
+test.ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Registering rotated log deletion for traffic.out with min roll count 0",
     "Verify traffic.out auto-delete configuration")
-test.ts.Streams.stderr += Testers.ContainsExpression(
+test.ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Registering rotated log deletion for diags.log with min roll count 0",
     "Verify diags.log auto-delete configuration")
-test.ts.Streams.stderr += Testers.ContainsExpression(
+test.ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Registering rotated log deletion for manager.log with min roll count 0",
     "Verify manager.log auto-delete configuration")
 # Verify test_deletion was rotated and deleted.
-test.ts.Streams.stderr += Testers.ExcludesExpression(
+test.ts.Disk.traffic_out.Content += Testers.ExcludesExpression(
     "The rolled logfile.*test_low_priority_deletion.log_.*was auto-deleted.*bytes were reclaimed",
     "Verify that space was reclaimed from test_high_priority_deletion")
 
 # Verify that ATS derives the hostname correctly if the user does not specify a
 # hostname via 'proxy.config.log.hostname'.
 hostname = socket.gethostname()
-test.ts.Streams.stderr += Testers.ContainsExpression(
+test.ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     f"The rolled logfile.*test_high_priority_deletion.log_{hostname}.*was auto-deleted.*bytes were reclaimed",
     "Verify that space was reclaimed from test_high_priority_deletion")
 
@@ -362,21 +362,21 @@ def get_command_to_rotate_thrice(self):
                         "Verify that the various min_count configurations behave as expected")
 
 # Only the test_deletion should have its min_count overridden.
-test.ts.Streams.stderr = Testers.ContainsExpression(
+test.ts.Disk.traffic_out.Content = Testers.ContainsExpression(
     "Registering rotated log deletion for error.log with min roll count 3",
     "Verify error.log auto-delete configuration")
-test.ts.Streams.stderr += Testers.ContainsExpression(
+test.ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Registering rotated log deletion for traffic.out with min roll count 4",
     "Verify traffic.out auto-delete configuration")
-test.ts.Streams.stderr += Testers.ContainsExpression(
+test.ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Registering rotated log deletion for diags.log with min roll count 5",
     "Verify diags.log auto-delete configuration")
-test.ts.Streams.stderr += Testers.ContainsExpression(
+test.ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Registering rotated log deletion for manager.log with min roll count 5",
     "Verify manager.log auto-delete configuration")
 # In case a future log is added, make sure the developer doesn't forget to
 # set the min count per configuration.
-test.ts.Streams.stderr += Testers.ExcludesExpression(
+test.ts.Disk.traffic_out.Content += Testers.ExcludesExpression(
     "Registering .* with min roll count 0",
     "Verify nothing has a default min roll count of 0 per configuration")
 
@@ -415,24 +415,24 @@ def get_command_to_rotate_thrice(self):
 )
 
 # Verify that each log type was registered for auto-deletion.
-test.ts.Streams.stderr = Testers.ExcludesExpression(
+test.ts.Disk.traffic_out.Content = Testers.ExcludesExpression(
     "Registering rotated log deletion for test_deletion.log with min roll count 1",
     "Verify test_deletion.log auto-delete configuration")
 # Only the test_deletion should have its min_count overridden.
-test.ts.Streams.stderr += Testers.ExcludesExpression(
+test.ts.Disk.traffic_out.Content += Testers.ExcludesExpression(
     "Registering rotated log deletion for error.log with min roll count 0",
     "Verify error.log auto-delete configuration")
-test.ts.Streams.stderr += Testers.ExcludesExpression(
+test.ts.Disk.traffic_out.Content += Testers.ExcludesExpression(
     "Registering rotated log deletion for traffic.out with min roll count 0",
     "Verify traffic.out auto-delete configuration")
-test.ts.Streams.stderr += Testers.ExcludesExpression(
+test.ts.Disk.traffic_out.Content += Testers.ExcludesExpression(
     "Registering rotated log deletion for diags.log with min roll count 0",
     "Verify diags.log auto-delete configuration")
-test.ts.Streams.stderr += Testers.ExcludesExpression(
+test.ts.Disk.traffic_out.Content += Testers.ExcludesExpression(
     "Registering rotated log deletion for manager.log with min roll count 0",
     "Verify manager.log auto-delete configuration")
 # Verify test_deletion was not deleted.
-test.ts.Streams.stderr += Testers.ExcludesExpression(
+test.ts.Disk.traffic_out.Content += Testers.ExcludesExpression(
     "The rolled logfile.*test_deletion.log_.*was auto-deleted.*bytes were reclaimed",
     "Verify that space was reclaimed")
 
@@ -472,7 +472,7 @@ def get_command_to_rotate_thrice(self):
 )
 
 # Verify that trim happened for the rolled file.
-test.ts.Streams.stderr = Testers.ContainsExpression(
+test.ts.Disk.traffic_out.Content = Testers.ContainsExpression(
     "rolled logfile.*test_deletion.log.*old.* was auto-deleted",
     "Verify test_deletion.log was trimmed")
 
@@ -500,23 +500,23 @@ def get_command_to_rotate_thrice(self):
 )
 
 # Verify that the plugin's logs and other core logs were registered for deletion.
-test.ts.Streams.stderr = Testers.ContainsExpression(
+test.ts.Disk.traffic_out.Content = Testers.ContainsExpression(
     "Registering rotated log deletion for test_deletion.log with min roll count 0",
     "Verify test_deletion.log auto-delete configuration")
-test.ts.Streams.stderr += Testers.ContainsExpression(
+test.ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Registering rotated log deletion for error.log with min roll count 0",
     "Verify error.log auto-delete configuration")
-test.ts.Streams.stderr += Testers.ContainsExpression(
+test.ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Registering rotated log deletion for traffic.out with min roll count 0",
     "Verify traffic.out auto-delete configuration")
-test.ts.Streams.stderr += Testers.ContainsExpression(
+test.ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Registering rotated log deletion for diags.log with min roll count 0",
     "Verify diags.log auto-delete configuration")
-test.ts.Streams.stderr += Testers.ContainsExpression(
+test.ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Registering rotated log deletion for manager.log with min roll count 0",
     "Verify manager.log auto-delete configuration")
 # Verify test_deletion was rotated and deleted.
-test.ts.Streams.stderr += Testers.ContainsExpression(
+test.ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "The rolled logfile.*test_deletion.log_.*was auto-deleted.*bytes were reclaimed",
     "Verify that space was reclaimed")
 
diff --git a/tests/gold_tests/next_hop/strategies_ch/strategies_ch.test.py b/tests/gold_tests/next_hop/strategies_ch/strategies_ch.test.py
index 88c8dde1807..4912007ed99 100644
--- a/tests/gold_tests/next_hop/strategies_ch/strategies_ch.test.py
+++ b/tests/gold_tests/next_hop/strategies_ch/strategies_ch.test.py
@@ -51,7 +51,7 @@
 num_nh = 8
 ts_nh = []
 for i in range(num_nh):
-    ts = Test.MakeATSProcess(f"ts_nh{i}", command=f"traffic_server 2>nh_trace{i}.log")
+    ts = Test.MakeATSProcess(f"ts_nh{i}", use_traffic_out=False, command=f"traffic_server 2>nh_trace{i}.log")
     ts.Disk.records_config.update({
         'proxy.config.diags.debug.enabled': 1,
         'proxy.config.diags.debug.tags': 'http|dns',
diff --git a/tests/gold_tests/next_hop/strategies_ch2/strategies_ch2.test.py b/tests/gold_tests/next_hop/strategies_ch2/strategies_ch2.test.py
index e451d42f981..9d7f9765298 100644
--- a/tests/gold_tests/next_hop/strategies_ch2/strategies_ch2.test.py
+++ b/tests/gold_tests/next_hop/strategies_ch2/strategies_ch2.test.py
@@ -63,7 +63,7 @@
     )
     ts_nh.append(ts)
 
-ts = Test.MakeATSProcess("ts", command="traffic_server 2> trace.log")
+ts = Test.MakeATSProcess("ts", use_traffic_out=False, command="traffic_server 2> trace.log")
 
 ts.Disk.records_config.update({
     'proxy.config.diags.debug.enabled': 1,
diff --git a/tests/gold_tests/next_hop/zzz_strategies_peer/zzz_strategies_peer.test.py b/tests/gold_tests/next_hop/zzz_strategies_peer/zzz_strategies_peer.test.py
index a6c262a584f..872d284e756 100644
--- a/tests/gold_tests/next_hop/zzz_strategies_peer/zzz_strategies_peer.test.py
+++ b/tests/gold_tests/next_hop/zzz_strategies_peer/zzz_strategies_peer.test.py
@@ -72,7 +72,7 @@
 num_peer = 8
 ts_peer = []
 for i in range(num_peer):
-    ts = Test.MakeATSProcess(f"ts_peer{i}", command=f"traffic_server 2> trace_peer{i}.log")
+    ts = Test.MakeATSProcess(f"ts_peer{i}", use_traffic_out=False, command=f"traffic_server 2> trace_peer{i}.log")
     ts_peer.append(ts)
 for i in range(num_peer):
     ts = ts_peer[i]
diff --git a/tests/gold_tests/next_hop/zzz_strategies_peer2/zzz_strategies_peer2.test.py b/tests/gold_tests/next_hop/zzz_strategies_peer2/zzz_strategies_peer2.test.py
index 20c4515e160..bf8edbb0047 100644
--- a/tests/gold_tests/next_hop/zzz_strategies_peer2/zzz_strategies_peer2.test.py
+++ b/tests/gold_tests/next_hop/zzz_strategies_peer2/zzz_strategies_peer2.test.py
@@ -72,7 +72,7 @@
 num_peer = 8
 ts_peer = []
 for i in range(num_peer):
-    ts = Test.MakeATSProcess(f"ts_peer{i}", command=f"traffic_server 2> trace_peer{i}.log")
+    ts = Test.MakeATSProcess(f"ts_peer{i}", use_traffic_out=False, command=f"traffic_server 2> trace_peer{i}.log")
     ts_peer.append(ts)
 for i in range(num_peer):
     ts = ts_peer[i]
diff --git a/tests/gold_tests/null_transform/null_transform.test.py b/tests/gold_tests/null_transform/null_transform.test.py
index 497c2c4dd11..25cd653e39f 100644
--- a/tests/gold_tests/null_transform/null_transform.test.py
+++ b/tests/gold_tests/null_transform/null_transform.test.py
@@ -67,4 +67,4 @@
 tr.StillRunningAfter = server
 
 # Check Plugin Loading Information
-ts.Streams.All = "gold/null_transform-tag.gold"
+ts.Disk.traffic_out.Content = "gold/null_transform-tag.gold"
diff --git a/tests/gold_tests/pluginTest/cert_update/cert_update.test.py b/tests/gold_tests/pluginTest/cert_update/cert_update.test.py
index dbda8bd335b..0b1af25e44b 100644
--- a/tests/gold_tests/pluginTest/cert_update/cert_update.test.py
+++ b/tests/gold_tests/pluginTest/cert_update/cert_update.test.py
@@ -93,7 +93,7 @@
 tr.Processes.Default.Command = (
     '{0}/traffic_ctl plugin msg cert_update.server {1}/server2.pem'.format(ts.Variables.BINDIR, ts.Variables.SSLDir)
 )
-ts.Streams.all = "gold/update.gold"
+ts.Disk.traffic_out.Content = "gold/update.gold"
 ts.StillRunningAfter = server
 
 # Server-Cert-After
@@ -127,7 +127,7 @@
     'mv {0}/client2.pem {0}/client1.pem && {1}/traffic_ctl plugin msg cert_update.client {0}/client1.pem'.format(
         ts.Variables.SSLDir, ts.Variables.BINDIR)
 )
-ts.Streams.all = "gold/update.gold"
+ts.Disk.traffic_out.Content = "gold/update.gold"
 ts.StillRunningAfter = server
 
 # Client-Cert-After
diff --git a/tests/gold_tests/pluginTest/header_rewrite/header_rewrite.test.py b/tests/gold_tests/pluginTest/header_rewrite/header_rewrite.test.py
index 923b8f1f3eb..c25b1841cea 100644
--- a/tests/gold_tests/pluginTest/header_rewrite/header_rewrite.test.py
+++ b/tests/gold_tests/pluginTest/header_rewrite/header_rewrite.test.py
@@ -58,4 +58,4 @@
 tr.Processes.Default.Streams.stderr = "gold/header_rewrite-303.gold"
 tr.StillRunningAfter = server
 
-ts.Streams.All = "gold/header_rewrite-tag.gold"
+ts.Disk.traffic_out.Content = "gold/header_rewrite-tag.gold"
diff --git a/tests/gold_tests/pluginTest/header_rewrite/header_rewrite_l_value.test.py b/tests/gold_tests/pluginTest/header_rewrite/header_rewrite_l_value.test.py
index 28247b02276..ead0a2323d4 100644
--- a/tests/gold_tests/pluginTest/header_rewrite/header_rewrite_l_value.test.py
+++ b/tests/gold_tests/pluginTest/header_rewrite/header_rewrite_l_value.test.py
@@ -61,4 +61,4 @@
 tr.Processes.Default.StartBefore(Test.Processes.ts)
 tr.Processes.Default.Streams.stderr = "gold/header_rewrite-l_value.gold"
 tr.StillRunningAfter = server
-ts.Streams.All = "gold/header_rewrite-tag.gold"
+ts.Disk.traffic_out.Content = "gold/header_rewrite-tag.gold"
diff --git a/tests/gold_tests/pluginTest/header_rewrite/header_rewrite_url.test.py b/tests/gold_tests/pluginTest/header_rewrite/header_rewrite_url.test.py
index 8f8427120e8..25ce462fc3b 100644
--- a/tests/gold_tests/pluginTest/header_rewrite/header_rewrite_url.test.py
+++ b/tests/gold_tests/pluginTest/header_rewrite/header_rewrite_url.test.py
@@ -68,7 +68,7 @@
 tr.Processes.Default.StartBefore(Test.Processes.ts)
 tr.Processes.Default.Streams.stderr = "gold/header_rewrite-client.gold"
 tr.StillRunningAfter = server
-ts.Streams.All = "gold/header_rewrite-tag.gold"
+ts.Disk.traffic_out.Content = "gold/header_rewrite-tag.gold"
 
 # Test TO-URL in a set-redirect operator.
 tr = Test.AddTestRun()
@@ -77,4 +77,4 @@
 tr.Processes.Default.ReturnCode = 0
 tr.Processes.Default.Streams.stderr = "gold/set-redirect.gold"
 tr.StillRunningAfter = server
-ts.Streams.All = "gold/header_rewrite-tag.gold"
+ts.Disk.traffic_out.Content = "gold/header_rewrite-tag.gold"
diff --git a/tests/gold_tests/pluginTest/lua/lifecycle_stats.sh b/tests/gold_tests/pluginTest/lua/lifecycle_stats.sh
index 764a1015d74..ad49469b4d4 100755
--- a/tests/gold_tests/pluginTest/lua/lifecycle_stats.sh
+++ b/tests/gold_tests/pluginTest/lua/lifecycle_stats.sh
@@ -20,7 +20,7 @@ while (( N > 0 ))
 do
     sleep 1
     rm -f lifecycle.out
-    grep -F ' ts_lua ' ts.stderr.txt | \
+    grep -F ' ts_lua ' ${PROXY_CONFIG_LOG_LOGFILE_DIR}/traffic.out | \
         sed -e 's/^.* ts_lua //' -e 's/ gc_kb:.*gc_kb_max:.*threads:.*threads_max:.*$//' > lifecycle.out
     if diff lifecycle.out ${AUTEST_TEST_DIR}/gold/lifecycle.gold > /dev/null
     then
diff --git a/tests/gold_tests/pluginTest/lua/lua_states_stats.test.py b/tests/gold_tests/pluginTest/lua/lua_states_stats.test.py
index 47dc09b6b01..7061f5eb83c 100644
--- a/tests/gold_tests/pluginTest/lua/lua_states_stats.test.py
+++ b/tests/gold_tests/pluginTest/lua/lua_states_stats.test.py
@@ -28,12 +28,7 @@
 # Define default ATS
 server = Test.MakeOriginServer("server")
 
-# It is necessary to redirect stderr to a file so it will be available for examination by a test run.
-ts = Test.MakeATSProcess(
-    "ts", command="traffic_manager 2> " + Test.RunDirectory + "/ts.stderr.txt", select_ports=True
-)
-# For unknown reasons, traffic_manager returns 2 instead of 0 on exit with stderr redirect here.
-ts.ReturnCode = 2
+ts = Test.MakeATSProcess("ts", command="traffic_manager", select_ports=True)
 
 Test.testName = "Lua states and stats"
 
diff --git a/tests/gold_tests/pluginTest/lua/lua_watermark.test.py b/tests/gold_tests/pluginTest/lua/lua_watermark.test.py
index b44004c37f5..b241cebae1f 100644
--- a/tests/gold_tests/pluginTest/lua/lua_watermark.test.py
+++ b/tests/gold_tests/pluginTest/lua/lua_watermark.test.py
@@ -55,7 +55,7 @@
 })
 
 # Test for watermark debug output
-ts.Streams.All = Testers.ContainsExpression(r"WMbytes\(31337\)", "Upstream watermark should be properly set")
+ts.Disk.traffic_out.Content = Testers.ContainsExpression(r"WMbytes\(31337\)", "Upstream watermark should be properly set")
 
 # Test if watermark upstream is set
 tr = Test.AddTestRun("Lua Watermark")
diff --git a/tests/gold_tests/pluginTest/parent_select/parent_select.test.py b/tests/gold_tests/pluginTest/parent_select/parent_select.test.py
index d93c8862687..1903e0722d2 100755
--- a/tests/gold_tests/pluginTest/parent_select/parent_select.test.py
+++ b/tests/gold_tests/pluginTest/parent_select/parent_select.test.py
@@ -56,7 +56,7 @@
 num_nh = 8
 ts_nh = []
 for i in range(num_nh):
-    ts = Test.MakeATSProcess(f"ts_nh{i}", command=f"traffic_server 2>nh_trace{i}.log")
+    ts = Test.MakeATSProcess(f"ts_nh{i}", use_traffic_out=False, command=f"traffic_server 2>nh_trace{i}.log")
     ts.Disk.records_config.update({
         'proxy.config.diags.debug.enabled': 1,
         'proxy.config.diags.debug.tags': 'http|dns',
diff --git a/tests/gold_tests/pluginTest/parent_select/parent_select_optional_scheme_matching.test.py b/tests/gold_tests/pluginTest/parent_select/parent_select_optional_scheme_matching.test.py
index c1754da0f99..4df05036b20 100755
--- a/tests/gold_tests/pluginTest/parent_select/parent_select_optional_scheme_matching.test.py
+++ b/tests/gold_tests/pluginTest/parent_select/parent_select_optional_scheme_matching.test.py
@@ -56,7 +56,7 @@
 num_nh = 8
 ts_nh = []
 for i in range(num_nh):
-    ts = Test.MakeATSProcess(f"ts_nh{i}", command=f"traffic_server 2>nh_trace{i}.log")
+    ts = Test.MakeATSProcess(f"ts_nh{i}", use_traffic_out=False, command=f"traffic_server 2>nh_trace{i}.log")
     ts.Disk.records_config.update({
         'proxy.config.diags.debug.enabled': 1,
         'proxy.config.diags.debug.tags': 'http|dns',
diff --git a/tests/gold_tests/pluginTest/parent_select/parent_select_peer.test.py b/tests/gold_tests/pluginTest/parent_select/parent_select_peer.test.py
index 989cd0f5b52..deec6a2d346 100644
--- a/tests/gold_tests/pluginTest/parent_select/parent_select_peer.test.py
+++ b/tests/gold_tests/pluginTest/parent_select/parent_select_peer.test.py
@@ -72,7 +72,7 @@
 num_peer = 8
 ts_peer = []
 for i in range(num_peer):
-    ts = Test.MakeATSProcess(f"ts_peer{i}", command=f"traffic_server 2> trace_peer{i}.log")
+    ts = Test.MakeATSProcess(f"ts_peer{i}", use_traffic_out=False, command=f"traffic_server 2> trace_peer{i}.log")
     ts_peer.append(ts)
 for i in range(num_peer):
     ts = ts_peer[i]
diff --git a/tests/gold_tests/pluginTest/parent_select/parent_select_peer2.test.py b/tests/gold_tests/pluginTest/parent_select/parent_select_peer2.test.py
index 1f25447f91e..25a7f9f6346 100644
--- a/tests/gold_tests/pluginTest/parent_select/parent_select_peer2.test.py
+++ b/tests/gold_tests/pluginTest/parent_select/parent_select_peer2.test.py
@@ -72,7 +72,7 @@
 num_peer = 8
 ts_peer = []
 for i in range(num_peer):
-    ts = Test.MakeATSProcess(f"ts_peer{i}", command=f"traffic_server 2> trace_peer{i}.log")
+    ts = Test.MakeATSProcess(f"ts_peer{i}", use_traffic_out=False, command=f"traffic_server 2> trace_peer{i}.log")
     ts_peer.append(ts)
 for i in range(num_peer):
     ts = ts_peer[i]
diff --git a/tests/gold_tests/pluginTest/prefetch_simple/prefetch_simple.test.py b/tests/gold_tests/pluginTest/prefetch_simple/prefetch_simple.test.py
index 70b0246e03c..79357f0285b 100644
--- a/tests/gold_tests/pluginTest/prefetch_simple/prefetch_simple.test.py
+++ b/tests/gold_tests/pluginTest/prefetch_simple/prefetch_simple.test.py
@@ -43,7 +43,7 @@
 
 dns = Test.MakeDNServer("dns")
 
-ts = Test.MakeATSProcess("ts", command="traffic_server 2> trace.log")
+ts = Test.MakeATSProcess("ts", use_traffic_out=False, command="traffic_server 2> trace.log")
 ts.Disk.records_config.update({
     'proxy.config.diags.debug.enabled': 1,
     'proxy.config.diags.debug.tags': 'http|dns|prefetch',
diff --git a/tests/gold_tests/pluginTest/stek_share/stek_share.test.py b/tests/gold_tests/pluginTest/stek_share/stek_share.test.py
index 50f2010022e..91c1b763a64 100644
--- a/tests/gold_tests/pluginTest/stek_share/stek_share.test.py
+++ b/tests/gold_tests/pluginTest/stek_share/stek_share.test.py
@@ -222,11 +222,11 @@ def check_session(ev, test):
 tr1.Processes.Default.StartBefore(ts4)
 tr1.Processes.Default.StartBefore(ts5)
 tr1.Processes.Default.Streams.All = Testers.ContainsExpression('curl test', 'Making sure the basics still work')
-ts1.Streams.All = Testers.ContainsExpression('Generate initial STEK succeeded', 'should succeed')
-ts2.Streams.All = Testers.ContainsExpression('Generate initial STEK succeeded', 'should succeed')
-ts3.Streams.All = Testers.ContainsExpression('Generate initial STEK succeeded', 'should succeed')
-ts4.Streams.All = Testers.ContainsExpression('Generate initial STEK succeeded', 'should succeed')
-ts5.Streams.All = Testers.ContainsExpression('Generate initial STEK succeeded', 'should succeed')
+ts1.Disk.traffic_out.Content = Testers.ContainsExpression('Generate initial STEK succeeded', 'should succeed')
+ts1.Disk.traffic_out.Content = Testers.ContainsExpression('Generate initial STEK succeeded', 'should succeed')
+ts1.Disk.traffic_out.Content = Testers.ContainsExpression('Generate initial STEK succeeded', 'should succeed')
+ts1.Disk.traffic_out.Content = Testers.ContainsExpression('Generate initial STEK succeeded', 'should succeed')
+ts1.Disk.traffic_out.Content = Testers.ContainsExpression('Generate initial STEK succeeded', 'should succeed')
 tr1.StillRunningAfter = server
 tr1.StillRunningAfter += ts1
 tr1.StillRunningAfter += ts2
diff --git a/tests/gold_tests/pluginTest/test_hooks/hook_add.test.py b/tests/gold_tests/pluginTest/test_hooks/hook_add.test.py
index 43e824247f5..3abac58b2e2 100644
--- a/tests/gold_tests/pluginTest/test_hooks/hook_add.test.py
+++ b/tests/gold_tests/pluginTest/test_hooks/hook_add.test.py
@@ -55,4 +55,4 @@
 tr.Processes.Default.ReturnCode = 0
 
 # Look at the debug output from the plugin
-ts.Streams.All = "hook_add.gold"
+ts.Disk.traffic_out.Content = "hook_add.gold"
diff --git a/tests/gold_tests/pluginTest/test_hooks/ssn_start_delay_hook.test.py b/tests/gold_tests/pluginTest/test_hooks/ssn_start_delay_hook.test.py
index 738630fdb4f..391f80ffada 100644
--- a/tests/gold_tests/pluginTest/test_hooks/ssn_start_delay_hook.test.py
+++ b/tests/gold_tests/pluginTest/test_hooks/ssn_start_delay_hook.test.py
@@ -57,4 +57,4 @@
 tr.Processes.Default.ReturnCode = 0
 
 # Look at the debug output from the plugin
-ts.Streams.All = "ssn_delay.gold"
+ts.Disk.traffic_out.Content = "ssn_delay.gold"
diff --git a/tests/gold_tests/pluginTest/traffic_dump/traffic_dump.test.py b/tests/gold_tests/pluginTest/traffic_dump/traffic_dump.test.py
index 1aa57e47f1a..620ec857ba3 100644
--- a/tests/gold_tests/pluginTest/traffic_dump/traffic_dump.test.py
+++ b/tests/gold_tests/pluginTest/traffic_dump/traffic_dump.test.py
@@ -98,16 +98,16 @@
 ts.Disk.diags_log.Content = Testers.ContainsExpression(
     "loading plugin.*traffic_dump.so",
     "Verify the traffic_dump plugin got loaded.")
-ts.Streams.stderr = Testers.ContainsExpression(
+ts.Disk.traffic_out.Content = Testers.ContainsExpression(
     f"Initialized with log directory: {replay_dir}",
     "Verify traffic_dump initialized with the configured directory.")
-ts.Streams.stderr += Testers.ContainsExpression(
+ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Initialized with sample pool size 1 bytes and disk limit 1000000000 bytes",
     "Verify traffic_dump initialized with the configured disk limit.")
-ts.Streams.stderr += Testers.ContainsExpression(
+ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Finish a session with log file of.*bytes",
     "Verify traffic_dump sees the end of sessions and accounts for it.")
-ts.Streams.stderr += Testers.ContainsExpression(
+ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Dumping body bytes: false",
     "Verify that dumping body bytes is enabled.")
 
diff --git a/tests/gold_tests/pluginTest/traffic_dump/traffic_dump_http3.test.py b/tests/gold_tests/pluginTest/traffic_dump/traffic_dump_http3.test.py
index c4c9bbfaaed..fa67411ad17 100644
--- a/tests/gold_tests/pluginTest/traffic_dump/traffic_dump_http3.test.py
+++ b/tests/gold_tests/pluginTest/traffic_dump/traffic_dump_http3.test.py
@@ -101,13 +101,13 @@
 ts.Disk.diags_log.Content = Testers.ContainsExpression(
     "loading plugin.*traffic_dump.so",
     "Verify the traffic_dump plugin got loaded.")
-ts.Streams.stderr = Testers.ContainsExpression(
+ts.Disk.traffic_out.Content = Testers.ContainsExpression(
     f"Initialized with log directory: {ts_log_dir}",
     "Verify traffic_dump initialized with the configured directory.")
-ts.Streams.stderr += Testers.ContainsExpression(
+ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Initialized with sample pool size 1 bytes and disk limit 1000000000 bytes",
     "Verify traffic_dump initialized with the configured disk limit.")
-ts.Streams.stderr += Testers.ContainsExpression(
+ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Finish a session with log file of.*bytes",
     "Verify traffic_dump sees the end of sessions and accounts for it.")
 
diff --git a/tests/gold_tests/pluginTest/traffic_dump/traffic_dump_ip_filter.test.py b/tests/gold_tests/pluginTest/traffic_dump/traffic_dump_ip_filter.test.py
index 12eeae0e15c..220e81249ea 100644
--- a/tests/gold_tests/pluginTest/traffic_dump/traffic_dump_ip_filter.test.py
+++ b/tests/gold_tests/pluginTest/traffic_dump/traffic_dump_ip_filter.test.py
@@ -75,7 +75,7 @@ def get_common_ats_process(name, plugin_command, replay_exists):
     "ts1",
     'traffic_dump.so --logdir {0} --sample 1 --limit 1000000000 -4 127.0.0.1',
     replay_exists=True)
-ts1.Streams.stderr += Testers.ContainsExpression(
+ts1.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Filtering to only dump connections with ip: 127.0.0.1",
     "Verify the IP filter status message.")
 tr.AddVerifierClientProcess(
@@ -103,7 +103,7 @@ def get_common_ats_process(name, plugin_command, replay_exists):
     "ts2",
     'traffic_dump.so --logdir {0} --sample 1 --limit 1000000000 -4 1.2.3.4',
     replay_exists=False)
-ts2.Streams.stderr += Testers.ContainsExpression(
+ts2.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Filtering to only dump connections with ip: 1.2.3.4",
     "Verify the IP filter status message.")
 tr.AddVerifierClientProcess(
diff --git a/tests/gold_tests/pluginTest/traffic_dump/traffic_dump_response_body.test.py b/tests/gold_tests/pluginTest/traffic_dump/traffic_dump_response_body.test.py
index 61538d13b71..a8e2be4e419 100644
--- a/tests/gold_tests/pluginTest/traffic_dump/traffic_dump_response_body.test.py
+++ b/tests/gold_tests/pluginTest/traffic_dump/traffic_dump_response_body.test.py
@@ -79,7 +79,7 @@
 ts_dump_3 = os.path.join(replay_dir, "127", "0000000000000003")
 ts.Disk.File(ts_dump_3, exists=True)
 
-ts.Streams.stderr = Testers.ContainsExpression(
+ts.Disk.traffic_out.Content = Testers.ContainsExpression(
     "Dumping body bytes: true",
     "Verify that dumping body bytes is enabled.")
 
diff --git a/tests/gold_tests/pluginTest/traffic_dump/traffic_dump_sni_filter.test.py b/tests/gold_tests/pluginTest/traffic_dump/traffic_dump_sni_filter.test.py
index 3f8b89c1b89..f1eac6bb883 100644
--- a/tests/gold_tests/pluginTest/traffic_dump/traffic_dump_sni_filter.test.py
+++ b/tests/gold_tests/pluginTest/traffic_dump/traffic_dump_sni_filter.test.py
@@ -79,11 +79,11 @@
 )
 
 # Set up trafficserver expectations.
-ts.Streams.stderr += Testers.ContainsExpression(
+ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     f"Filtering to only dump connections with SNI: {sni_filter}",
     "Verify filtering for the expected SNI.")
 
-ts.Streams.stderr += Testers.ContainsExpression(
+ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Ignore HTTPS session with non-filtered SNI: dave",
     "Verify that the non-desired SNI session was filtered out.")
 
diff --git a/tests/gold_tests/pluginTest/transform/transaction_data_sink.test.py b/tests/gold_tests/pluginTest/transform/transaction_data_sink.test.py
index 8162d62ae20..172cc1c8738 100644
--- a/tests/gold_tests/pluginTest/transform/transaction_data_sink.test.py
+++ b/tests/gold_tests/pluginTest/transform/transaction_data_sink.test.py
@@ -41,7 +41,7 @@
 
 # Verify that the various aspects of the expected debug output for the
 # transaction are logged.
-ts.Streams.stderr = Testers.ContainsExpression(
+ts.Disk.traffic_out.Content = Testers.ContainsExpression(
     '"http1.1_response_body"',
     "The response body should be printed by the plugin.")
 
diff --git a/tests/gold_tests/pluginTest/uri_signing/uri_signing.test.py b/tests/gold_tests/pluginTest/uri_signing/uri_signing.test.py
index b85f9872562..1208cbf632b 100644
--- a/tests/gold_tests/pluginTest/uri_signing/uri_signing.test.py
+++ b/tests/gold_tests/pluginTest/uri_signing/uri_signing.test.py
@@ -211,6 +211,8 @@
 ps.Command = curl_and_args + '"http://somehost/someasset.ts?URISigningPackage=ewogICJ0eXAiOiAiSldUIiwKICAiYWxnIjogIkhTMjU2Igp9.ewogICJleHAiOiAxOTIzMDU2MDg0Cn0.zw_wFQ-wvrWmfPLGj3hAUWn-GOHkiJZi2but4KV0paY"'
 ps.ReturnCode = 0
 ps.Streams.stderr = "gold/403.gold"
-ts.Streams.stderr = Testers.ContainsExpression("Initial JWT Failure: iss is missing, must be present", "should fail the validation")
+ts.Disk.traffic_out.Content = Testers.ContainsExpression(
+    "Initial JWT Failure: iss is missing, must be present",
+    "should fail the validation")
 tr.StillRunningAfter = server
 tr.StillRunningAfter = ts
diff --git a/tests/gold_tests/session_sharing/session_match.test.py b/tests/gold_tests/session_sharing/session_match.test.py
index 2d95d7c3ebf..b7409b086de 100644
--- a/tests/gold_tests/session_sharing/session_match.test.py
+++ b/tests/gold_tests/session_sharing/session_match.test.py
@@ -82,13 +82,13 @@ def _runTraffic(self):
 
     def runAndExpectSharing(self):
         self._runTraffic()
-        self._ts.Streams.stderr = Testers.ContainsExpression(
+        self._ts.Disk.traffic_out.Content = Testers.ContainsExpression(
             "global pool search successful",
             "Verify that sessions got shared")
 
     def runAndExpectNoSharing(self):
         self._runTraffic()
-        self._ts.Streams.stderr = Testers.ExcludesExpression(
+        self._ts.Disk.traffic_out.Content = Testers.ExcludesExpression(
             "global pool search successful",
             "Verify that sessions did not get shared")
 
diff --git a/tests/gold_tests/shutdown/emergency.test.py b/tests/gold_tests/shutdown/emergency.test.py
index 343ca2606ff..3e4d9abdef4 100644
--- a/tests/gold_tests/shutdown/emergency.test.py
+++ b/tests/gold_tests/shutdown/emergency.test.py
@@ -47,5 +47,5 @@
 tr.Processes.Default.StartBefore(ts)
 ts.ReturnCode = 33
 ts.Ready = 0  # Need this to be 0 because we are testing shutdown, this is to make autest not think ats went away for a bad reason.
-ts.Streams.All = Testers.ExcludesExpression('failed to shutdown', 'should NOT contain "failed to shutdown"')
+ts.Disk.traffic_out.Content = Testers.ExcludesExpression('failed to shutdown', 'should NOT contain "failed to shutdown"')
 ts.Disk.diags_log.Content = Testers.IncludesExpression('testing emergency shutdown', 'should contain "testing emergency shutdown"')
diff --git a/tests/gold_tests/shutdown/fatal.test.py b/tests/gold_tests/shutdown/fatal.test.py
index 972a73a3fe8..a36ea44e515 100644
--- a/tests/gold_tests/shutdown/fatal.test.py
+++ b/tests/gold_tests/shutdown/fatal.test.py
@@ -47,5 +47,5 @@
 tr.Processes.Default.StartBefore(ts)
 ts.ReturnCode = 70
 ts.Ready = 0  # Need this to be 0 because we are testing shutdown, this is to make autest not think ats went away for a bad reason.
-ts.Streams.All = Testers.ExcludesExpression('failed to shutdown', 'should NOT contain "failed to shutdown"')
+ts.Disk.traffic_out.Content = Testers.ExcludesExpression('failed to shutdown', 'should NOT contain "failed to shutdown"')
 ts.Disk.diags_log.Content = Testers.IncludesExpression('testing fatal shutdown', 'should contain "testing fatal shutdown"')
diff --git a/tests/gold_tests/tls/ssl_multicert_loader.test.py b/tests/gold_tests/tls/ssl_multicert_loader.test.py
index 1c79e7cd082..6d8b2f5a006 100644
--- a/tests/gold_tests/tls/ssl_multicert_loader.test.py
+++ b/tests/gold_tests/tls/ssl_multicert_loader.test.py
@@ -107,7 +107,7 @@
 
 ts2.ReturnCode = 2
 ts2.Ready = 0  # Need this to be 0 because we are testing shutdown, this is to make autest not think ats went away for a bad reason.
-ts2.Streams.All = Testers.ExcludesExpression(
+ts.Disk.traffic_out.Content = Testers.ExcludesExpression(
     'Traffic Server is fully initialized',
     'process should fail when invalid certificate specified')
 ts2.Disk.diags_log.Content = Testers.IncludesExpression('FATAL: failed to load SSL certificate file', 'check diags.log"')
diff --git a/tests/gold_tests/tls/tls_engine.test.py b/tests/gold_tests/tls/tls_engine.test.py
index 7ff16b3328f..493ece17c4b 100644
--- a/tests/gold_tests/tls/tls_engine.test.py
+++ b/tests/gold_tests/tls/tls_engine.test.py
@@ -99,4 +99,4 @@
 tr.Processes.Default.Streams.All = Testers.ContainsExpression(r"HTTP/(2|1\.1) 200", "Request succeeds")
 tr.StillRunningAfter = server
 
-ts.Streams.All += Testers.ContainsExpression("Send signal to ", "The Async engine triggers")
+ts.Disk.traffic_out.Content += Testers.ContainsExpression("Send signal to ", "The Async engine triggers")
diff --git a/tests/gold_tests/tls/tls_hooks_client_verify.test.py b/tests/gold_tests/tls/tls_hooks_client_verify.test.py
index cd428dc2f8b..94838625a59 100644
--- a/tests/gold_tests/tls/tls_hooks_client_verify.test.py
+++ b/tests/gold_tests/tls/tls_hooks_client_verify.test.py
@@ -104,11 +104,11 @@
 tr3.Processes.Default.ReturnCode = 35
 tr3.Processes.Default.Streams.all = Testers.ContainsExpression("error", "Curl attempt should have failed")
 
-ts.Streams.All += Testers.ContainsExpression(
+ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Client verify callback 0 [\da-fx]+? - event is good good HS", "verify callback happens 2 times")
-ts.Streams.All += Testers.ContainsExpression(
+ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Client verify callback 1 [\da-fx]+? - event is good good HS", "verify callback happens 2 times")
-ts.Streams.All += Testers.ContainsExpression(
+ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Client verify callback 0 [\da-fx]+? - event is good error HS", "verify callback happens 2 times")
-ts.Streams.All += Testers.ContainsExpression(
+ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Client verify callback 1 [\da-fx]+? - event is good error HS", "verify callback happens 2 times")
diff --git a/tests/gold_tests/tls/tls_hooks_verify.test.py b/tests/gold_tests/tls/tls_hooks_verify.test.py
index 7df8ec0eca3..6d5c39d8a30 100644
--- a/tests/gold_tests/tls/tls_hooks_verify.test.py
+++ b/tests/gold_tests/tls/tls_hooks_verify.test.py
@@ -101,16 +101,16 @@
     "bar.com should fail but continue")
 ts.Disk.diags_log.Content += Testers.ExcludesExpression("SNI=foo.com", "foo.com should not fail in any way")
 
-ts.Streams.All += Testers.ContainsExpression(
+ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Server verify callback 0 [\da-fx]+? - event is good SNI=foo.com good HS", "verify callback happens 2 times")
-ts.Streams.All += Testers.ContainsExpression(
+ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Server verify callback 1 [\da-fx]+? - event is good SNI=foo.com good HS", "verify callback happens 2 times")
-ts.Streams.All += Testers.ContainsExpression(
+ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Server verify callback 0 [\da-fx]+? - event is good SNI=random.com error HS", "verify callback happens 2 times")
-ts.Streams.All += Testers.ContainsExpression(
+ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Server verify callback 1 [\da-fx]+? - event is good SNI=random.com error HS", "verify callback happens 2 times")
-ts.Streams.All += Testers.ContainsExpression(
+ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Server verify callback 0 [\da-fx]+? - event is good SNI=bar.com error HS", "verify callback happens 2 times")
-ts.Streams.All += Testers.ContainsExpression(
+ts.Disk.traffic_out.Content += Testers.ContainsExpression(
     "Server verify callback 1 [\da-fx]+? - event is good SNI=bar.com error HS", "verify callback happens 2 times")
-ts.Streams.All += Testers.ContainsExpression("Server verify callback SNI APIs match=true", "verify SNI names match")
+ts.Disk.traffic_out.Content += Testers.ContainsExpression("Server verify callback SNI APIs match=true", "verify SNI names match")
diff --git a/tests/gold_tests/tls/tls_origin_session_reuse.test.py b/tests/gold_tests/tls/tls_origin_session_reuse.test.py
index 0595d6ecdf3..6c4a95bf69c 100644
--- a/tests/gold_tests/tls/tls_origin_session_reuse.test.py
+++ b/tests/gold_tests/tls/tls_origin_session_reuse.test.py
@@ -155,8 +155,8 @@
 tr.Processes.Default.StartBefore(ts1)
 tr.Processes.Default.StartBefore(ts2)
 tr.Processes.Default.Streams.All = Testers.ContainsExpression('curl test', 'Making sure the basics still work')
-ts2.Streams.All = Testers.ContainsExpression('new session to origin', '')
-ts2.Streams.All += Testers.ContainsExpression('reused session to origin', '')
+ts2.Disk.traffic_out.Content = Testers.ContainsExpression('new session to origin', '')
+ts2.Disk.traffic_out.Content += Testers.ContainsExpression('reused session to origin', '')
 tr.StillRunningAfter = server
 tr.StillRunningAfter += ts1
 tr.StillRunningAfter += ts2
@@ -166,9 +166,9 @@
     ts2.Variables.ssl_port)
 tr.Processes.Default.ReturnCode = 0
 tr.Processes.Default.Streams.All = Testers.ContainsExpression('curl test', 'Making sure the basics still work')
-ts2.Streams.All = Testers.ContainsExpression('remove oldest session', '')
-ts2.Streams.All += Testers.ContainsExpression('new session to origin', '')
-ts2.Streams.All += Testers.ContainsExpression('reused session to origin', '')
+ts2.Disk.traffic_out.Content = Testers.ContainsExpression('remove oldest session', '')
+ts2.Disk.traffic_out.Content += Testers.ContainsExpression('new session to origin', '')
+ts2.Disk.traffic_out.Content += Testers.ContainsExpression('reused session to origin', '')
 tr.StillRunningAfter = server
 
 tr = Test.AddTestRun('disable origin session reuse, reuse should fail')
@@ -177,5 +177,5 @@
 tr.Processes.Default.StartBefore(ts3)
 tr.Processes.Default.StartBefore(ts4)
 tr.Processes.Default.Streams.All = Testers.ContainsExpression('curl test', 'Making sure the basics still work')
-ts4.Streams.All = Testers.ContainsExpression('new session to origin', '')
-ts4.Streams.All += Testers.ExcludesExpression('reused session to origin', '')
+ts4.Disk.traffic_out.Content = Testers.ContainsExpression('new session to origin', '')
+ts4.Disk.traffic_out.Content += Testers.ExcludesExpression('reused session to origin', '')
diff --git a/tests/gold_tests/tls_hooks/gold/ts-close-out-close.gold b/tests/gold_tests/tls_hooks/gold/ts-close-out-close.gold
index c03962ead36..1025be21614 100644
--- a/tests/gold_tests/tls_hooks/gold/ts-close-out-close.gold
+++ b/tests/gold_tests/tls_hooks/gold/ts-close-out-close.gold
@@ -1,3 +1,4 @@
 `` DIAG: (ssl_hook_test) Outbound close callback `` - event is good
 `` DIAG: (ssl_hook_test) Close callback 0 `` - event is good
 `` DIAG: (ssl_hook_test) Close callback 1 `` - event is good
+``
diff --git a/tests/gold_tests/tls_hooks/tls_hooks.test.py b/tests/gold_tests/tls_hooks/tls_hooks.test.py
index 8d1ae9ce267..72c08bd6730 100644
--- a/tests/gold_tests/tls_hooks/tls_hooks.test.py
+++ b/tests/gold_tests/tls_hooks/tls_hooks.test.py
@@ -62,11 +62,11 @@
 tr.Processes.Default.Streams.All = Testers.ExcludesExpression(
     "TLSv1.3 (IN), TLS handshake, Finished (20):", "Should not negotiate a TLSv1.3 connection")
 
-ts.Streams.stderr = "gold/ts-preaccept-1.gold"
+ts.Disk.traffic_out.Content = "gold/ts-preaccept-1.gold"
 
 # the preaccept may get triggered twice because the test framework creates a TCP connection before handing off to traffic_server
 preacceptstring = "Pre accept callback 0"
-ts.Streams.All = Testers.ContainsExpression(
+ts.Disk.traffic_out.Content = Testers.ContainsExpression(
     r"\A(?:(?!{0}).)*{0}.*({0})?(?!.*{0}).*\Z".format(preacceptstring),
     "Pre accept message appears only once or twice",
     reflags=re.S | re.M)
diff --git a/tests/gold_tests/tls_hooks/tls_hooks10.test.py b/tests/gold_tests/tls_hooks/tls_hooks10.test.py
index e225e04ae65..8664240195c 100644
--- a/tests/gold_tests/tls_hooks/tls_hooks10.test.py
+++ b/tests/gold_tests/tls_hooks/tls_hooks10.test.py
@@ -56,7 +56,7 @@
 tr.Processes.Default.Command = 'curl -k -H \'host:example.com:{0}\' https://127.0.0.1:{0}'.format(ts.Variables.ssl_port)
 tr.Processes.Default.ReturnCode = 0
 
-ts.Streams.stderr = "gold/ts-cert-1-im-2.gold"
+ts.Disk.traffic_out.Content = "gold/ts-cert-1-im-2.gold"
 
 tr.Processes.Default.TimeOut = 15
 tr.TimeOut = 15
diff --git a/tests/gold_tests/tls_hooks/tls_hooks11.test.py b/tests/gold_tests/tls_hooks/tls_hooks11.test.py
index 1bc434a343d..1edf8d6a906 100644
--- a/tests/gold_tests/tls_hooks/tls_hooks11.test.py
+++ b/tests/gold_tests/tls_hooks/tls_hooks11.test.py
@@ -58,10 +58,10 @@
 tr.Processes.Default.ReturnCode = 0
 tr.Processes.Default.Streams.stdout = "gold/preaccept-1.gold"
 
-ts.Streams.stderr = "gold/ts-preaccept-delayed-1.gold"
+ts.Disk.traffic_out.Content = "gold/ts-preaccept-delayed-1.gold"
 
 preacceptstring = "Pre accept delay callback 0"
-ts.Streams.All = Testers.ContainsExpression(
+ts.Disk.traffic_out.Content = Testers.ContainsExpression(
     r"\A(?:(?!{0}).)*{0}.*({0})?(?!.*{0}).*\Z".format(preacceptstring),
     "Pre accept message appears only once or twice",
     reflags=re.S | re.M)
diff --git a/tests/gold_tests/tls_hooks/tls_hooks12.test.py b/tests/gold_tests/tls_hooks/tls_hooks12.test.py
index 0b1490f15ed..13b2a432d97 100644
--- a/tests/gold_tests/tls_hooks/tls_hooks12.test.py
+++ b/tests/gold_tests/tls_hooks/tls_hooks12.test.py
@@ -56,7 +56,7 @@
 tr.Processes.Default.Command = 'curl -k -H \'host:example.com:{0}\' https://127.0.0.1:{0}'.format(ts.Variables.ssl_port)
 tr.Processes.Default.ReturnCode = 0
 
-ts.Streams.stderr = "gold/ts-preaccept-delayed-1-immdate-2.gold"
+ts.Disk.traffic_out.Content = "gold/ts-preaccept-delayed-1-immdate-2.gold"
 
 tr.Processes.Default.TimeOut = 15
 tr.TimeOut = 15
diff --git a/tests/gold_tests/tls_hooks/tls_hooks13.test.py b/tests/gold_tests/tls_hooks/tls_hooks13.test.py
index cb69bbf9b64..cf72317e1c4 100644
--- a/tests/gold_tests/tls_hooks/tls_hooks13.test.py
+++ b/tests/gold_tests/tls_hooks/tls_hooks13.test.py
@@ -56,7 +56,7 @@
 tr.Processes.Default.Command = 'curl -k -H \'host:example.com:{0}\' https://127.0.0.1:{0}'.format(ts.Variables.ssl_port)
 tr.Processes.Default.ReturnCode = 0
 
-ts.Streams.stderr = "gold/ts-out-start-close-2.gold"
+ts.Disk.traffic_out.Content = "gold/ts-out-start-close-2.gold"
 
 tr.Processes.Default.TimeOut = 15
 tr.TimeOut = 15
diff --git a/tests/gold_tests/tls_hooks/tls_hooks14.test.py b/tests/gold_tests/tls_hooks/tls_hooks14.test.py
index e6c9ca06670..224069d241b 100644
--- a/tests/gold_tests/tls_hooks/tls_hooks14.test.py
+++ b/tests/gold_tests/tls_hooks/tls_hooks14.test.py
@@ -57,7 +57,7 @@
 tr.Processes.Default.Command = 'curl -k -H \'host:example.com:{0}\' https://127.0.0.1:{0}'.format(ts.Variables.ssl_port)
 tr.Processes.Default.ReturnCode = 0
 
-ts.Streams.stderr = "gold/ts-out-delay-start-2.gold"
+ts.Disk.traffic_out.Content = "gold/ts-out-delay-start-2.gold"
 
 tr.Processes.Default.TimeOut = 15
 tr.TimeOut = 15
diff --git a/tests/gold_tests/tls_hooks/tls_hooks15.test.py b/tests/gold_tests/tls_hooks/tls_hooks15.test.py
index 1c3cbd32e09..ba474006305 100644
--- a/tests/gold_tests/tls_hooks/tls_hooks15.test.py
+++ b/tests/gold_tests/tls_hooks/tls_hooks15.test.py
@@ -56,7 +56,7 @@
 tr.Processes.Default.Command = 'curl -k -H \'host:example.com:{0}\' https://127.0.0.1:{0}'.format(ts.Variables.ssl_port)
 tr.Processes.Default.ReturnCode = 0
 
-ts.Streams.stderr = "gold/ts-close-out-close.gold"
+ts.Disk.traffic_out.Content = "gold/ts-close-out-close.gold"
 
 tr.Processes.Default.TimeOut = 15
 tr.TimeOut = 15
diff --git a/tests/gold_tests/tls_hooks/tls_hooks16.test.py b/tests/gold_tests/tls_hooks/tls_hooks16.test.py
index 844330f20a8..84b96c68d55 100644
--- a/tests/gold_tests/tls_hooks/tls_hooks16.test.py
+++ b/tests/gold_tests/tls_hooks/tls_hooks16.test.py
@@ -62,10 +62,10 @@
 tr.Processes.Default.ReturnCode = 0
 tr.Processes.Default.Streams.stdout = "gold/client-hello-1.gold"
 
-ts.Streams.stderr = "gold/ts-client-hello-1.gold"
+ts.Disk.traffic_out.Content = "gold/ts-client-hello-1.gold"
 
 snistring = "Client Hello callback 0"
-ts.Streams.All = Testers.ContainsExpression(
+ts.Disk.traffic_out.Content = Testers.ContainsExpression(
     "\A(?:(?!{0}).)*{0}(?!.*{0}).*\Z".format(snistring), "Client Hello message appears only once", reflags=re.S | re.M)
 
 tr.Processes.Default.TimeOut = 15
diff --git a/tests/gold_tests/tls_hooks/tls_hooks17.test.py b/tests/gold_tests/tls_hooks/tls_hooks17.test.py
index e368168f645..4d78a00c6a7 100644
--- a/tests/gold_tests/tls_hooks/tls_hooks17.test.py
+++ b/tests/gold_tests/tls_hooks/tls_hooks17.test.py
@@ -63,10 +63,10 @@
 tr.Processes.Default.ReturnCode = 0
 tr.Processes.Default.Streams.stdout = "gold/client-hello-1.gold"
 
-ts.Streams.stderr = "gold/ts-client-hello-delayed-1.gold"
+ts.Disk.traffic_out.Content = "gold/ts-client-hello-delayed-1.gold"
 
 snistring = "Client Hello callback 0"
-ts.Streams.All = Testers.ContainsExpression(
+ts.Disk.traffic_out.Content = Testers.ContainsExpression(
     "\A(?:(?!{0}).)*{0}(?!.*{0}).*\Z".format(snistring), "Client Hello message appears only once", reflags=re.S | re.M)
 
 tr.Processes.Default.TimeOut = 15
diff --git a/tests/gold_tests/tls_hooks/tls_hooks18.test.py b/tests/gold_tests/tls_hooks/tls_hooks18.test.py
index 5b49a3ce27f..b4c028d79d4 100644
--- a/tests/gold_tests/tls_hooks/tls_hooks18.test.py
+++ b/tests/gold_tests/tls_hooks/tls_hooks18.test.py
@@ -63,13 +63,13 @@
 tr.Processes.Default.ReturnCode = 0
 tr.Processes.Default.Streams.stdout = "gold/preaccept-1.gold"
 
-ts.Streams.stderr = "gold/ts-client-hello-2.gold"
+ts.Disk.traffic_out.Content = "gold/ts-client-hello-2.gold"
 
 certstring0 = "Client Hello callback 0"
 certstring1 = "Client Hello callback 1"
-ts.Streams.All = Testers.ContainsExpression(
+ts.Disk.traffic_out.Content = Testers.ContainsExpression(
     "\A(?:(?!{0}).)*{0}(?!.*{0}).*\Z".format(certstring0), "Cert message appears only once", reflags=re.S | re.M)
-ts.Streams.All = Testers.ContainsExpression(
+ts.Disk.traffic_out.Content = Testers.ContainsExpression(
     "\A(?:(?!{0}).)*{0}(?!.*{0}).*\Z".format(certstring1), "Cert message appears only once", reflags=re.S | re.M)
 
 tr.Processes.Default.TimeOut = 15
diff --git a/tests/gold_tests/tls_hooks/tls_hooks2.test.py b/tests/gold_tests/tls_hooks/tls_hooks2.test.py
index 6b248c38c48..19a5c9f2d6a 100644
--- a/tests/gold_tests/tls_hooks/tls_hooks2.test.py
+++ b/tests/gold_tests/tls_hooks/tls_hooks2.test.py
@@ -58,10 +58,10 @@
 tr.Processes.Default.ReturnCode = 0
 tr.Processes.Default.Streams.stdout = "gold/preaccept-1.gold"
 
-ts.Streams.stderr = "gold/ts-sni-1.gold"
+ts.Disk.traffic_out.Content = "gold/ts-sni-1.gold"
 
 snistring = "SNI callback 0"
-ts.Streams.All = Testers.ContainsExpression(
+ts.Disk.traffic_out.Content = Testers.ContainsExpression(
     "\A(?:(?!{0}).)*{0}(?!.*{0}).*\Z".format(snistring), "SNI message appears only once", reflags=re.S | re.M)
 
 tr.Processes.Default.TimeOut = 15
diff --git a/tests/gold_tests/tls_hooks/tls_hooks3.test.py b/tests/gold_tests/tls_hooks/tls_hooks3.test.py
index 36cac3cfba3..9a39c4b31a9 100644
--- a/tests/gold_tests/tls_hooks/tls_hooks3.test.py
+++ b/tests/gold_tests/tls_hooks/tls_hooks3.test.py
@@ -58,10 +58,10 @@
 tr.Processes.Default.ReturnCode = 0
 tr.Processes.Default.Streams.stdout = "gold/preaccept-1.gold"
 
-ts.Streams.stderr = "gold/ts-cert-1.gold"
+ts.Disk.traffic_out.Content = "gold/ts-cert-1.gold"
 
 certstring = "Cert callback 0"
-ts.Streams.All = Testers.ContainsExpression(
+ts.Disk.traffic_out.Content = Testers.ContainsExpression(
     "\A(?:(?!{0}).)*{0}(?!.*{0}).*\Z".format(certstring), "Cert message appears only once", reflags=re.S | re.M)
 
 tr.Processes.Default.TimeOut = 15
diff --git a/tests/gold_tests/tls_hooks/tls_hooks4.test.py b/tests/gold_tests/tls_hooks/tls_hooks4.test.py
index 2cf5c95aa1b..085b870b01a 100644
--- a/tests/gold_tests/tls_hooks/tls_hooks4.test.py
+++ b/tests/gold_tests/tls_hooks/tls_hooks4.test.py
@@ -58,17 +58,17 @@
 tr.Processes.Default.ReturnCode = 0
 tr.Processes.Default.Streams.stdout = "gold/preaccept-1.gold"
 
-ts.Streams.stderr = "gold/ts-preaccept1-sni1-cert1.gold"
+ts.Disk.traffic_out.Content = "gold/ts-preaccept1-sni1-cert1.gold"
 snistring = "SNI callback 0"
 preacceptstring = "Pre accept callback 0"
 certstring = "Cert callback 0"
-ts.Streams.All = Testers.ContainsExpression(
+ts.Disk.traffic_out.Content = Testers.ContainsExpression(
     "\A(?:(?!{0}).)*{0}(?!.*{0}).*\Z".format(snistring), "SNI message appears only once", reflags=re.S | re.M)
 # the preaccept may get triggered twice because the test framework creates a TCP connection before handing off to traffic_server
-ts.Streams.All += Testers.ContainsExpression("\A(?:(?!{0}).)*{0}.*({0})?(?!.*{0}).*\Z".format(
+ts.Disk.traffic_out.Content += Testers.ContainsExpression("\A(?:(?!{0}).)*{0}.*({0})?(?!.*{0}).*\Z".format(
     preacceptstring), "Pre accept message appears only once or twice", reflags=re.S | re.M)
-ts.Streams.All += Testers.ContainsExpression("\A(?:(?!{0}).)*{0}(?!.*{0}).*\Z".format(certstring),
-                                             "Cert message appears only once", reflags=re.S | re.M)
+ts.Disk.traffic_out.Content += Testers.ContainsExpression("\A(?:(?!{0}).)*{0}(?!.*{0}).*\Z".format(certstring),
+                                                          "Cert message appears only once", reflags=re.S | re.M)
 
 tr.Processes.Default.TimeOut = 15
 tr.TimeOut = 15
diff --git a/tests/gold_tests/tls_hooks/tls_hooks6.test.py b/tests/gold_tests/tls_hooks/tls_hooks6.test.py
index a95974c997b..85038bdff62 100644
--- a/tests/gold_tests/tls_hooks/tls_hooks6.test.py
+++ b/tests/gold_tests/tls_hooks/tls_hooks6.test.py
@@ -58,16 +58,16 @@
 tr.Processes.Default.ReturnCode = 0
 tr.Processes.Default.Streams.stdout = "gold/preaccept-1.gold"
 
-ts.Streams.stderr = "gold/ts-preaccept-2.gold"
+ts.Disk.traffic_out.Content = "gold/ts-preaccept-2.gold"
 
 # the preaccept may get triggered twice because the test framework creates a TCP connection before handing off to traffic_server
 preacceptstring0 = "Pre accept callback 0"
 preacceptstring1 = "Pre accept callback 1"
-ts.Streams.All = Testers.ContainsExpression(
+ts.Disk.traffic_out.Content = Testers.ContainsExpression(
     r"\A(?:(?!{0}).)*{0}.*({0})?(?!.*{0}).*\Z".format(preacceptstring0),
     "Pre accept message appears only once or twice",
     reflags=re.S | re.M)
-ts.Streams.All = Testers.ContainsExpression(
+ts.Disk.traffic_out.Content = Testers.ContainsExpression(
     r"\A(?:(?!{0}).)*{0}.*({0})?(?!.*{0}).*\Z".format(preacceptstring1),
     "Pre accept message appears only once or twice",
     reflags=re.S | re.M)
diff --git a/tests/gold_tests/tls_hooks/tls_hooks7.test.py b/tests/gold_tests/tls_hooks/tls_hooks7.test.py
index fa5fb680c69..477aa256e24 100644
--- a/tests/gold_tests/tls_hooks/tls_hooks7.test.py
+++ b/tests/gold_tests/tls_hooks/tls_hooks7.test.py
@@ -58,13 +58,13 @@
 tr.Processes.Default.ReturnCode = 0
 tr.Processes.Default.Streams.stdout = "gold/preaccept-1.gold"
 
-ts.Streams.stderr = "gold/ts-sni-2.gold"
+ts.Disk.traffic_out.Content = "gold/ts-sni-2.gold"
 
 snistring0 = "SNI callback 0"
 snistring1 = "SNI callback 1"
-ts.Streams.All = Testers.ContainsExpression(
+ts.Disk.traffic_out.Content = Testers.ContainsExpression(
     "\A(?:(?!{0}).)*{0}(?!.*{0}).*\Z".format(snistring0), "SNI message appears only once", reflags=re.S | re.M)
-ts.Streams.All = Testers.ContainsExpression(
+ts.Disk.traffic_out.Content = Testers.ContainsExpression(
     "\A(?:(?!{0}).)*{0}(?!.*{0}).*\Z".format(snistring1), "SNI message appears only once", reflags=re.S | re.M)
 
 tr.Processes.Default.TimeOut = 15
diff --git a/tests/gold_tests/tls_hooks/tls_hooks8.test.py b/tests/gold_tests/tls_hooks/tls_hooks8.test.py
index 2df7639dfdb..a3c101c97f6 100644
--- a/tests/gold_tests/tls_hooks/tls_hooks8.test.py
+++ b/tests/gold_tests/tls_hooks/tls_hooks8.test.py
@@ -58,13 +58,13 @@
 tr.Processes.Default.ReturnCode = 0
 tr.Processes.Default.Streams.stdout = "gold/preaccept-1.gold"
 
-ts.Streams.stderr = "gold/ts-cert-2.gold"
+ts.Disk.traffic_out.Content = "gold/ts-cert-2.gold"
 
 certstring0 = "Cert callback 0"
 certstring1 = "Cert callback 1"
-ts.Streams.All = Testers.ContainsExpression(
+ts.Disk.traffic_out.Content = Testers.ContainsExpression(
     "\A(?:(?!{0}).)*{0}(?!.*{0}).*\Z".format(certstring0), "Cert message appears only once", reflags=re.S | re.M)
-ts.Streams.All = Testers.ContainsExpression(
+ts.Disk.traffic_out.Content = Testers.ContainsExpression(
     "\A(?:(?!{0}).)*{0}(?!.*{0}).*\Z".format(certstring1), "Cert message appears only once", reflags=re.S | re.M)
 
 tr.Processes.Default.TimeOut = 15
diff --git a/tests/gold_tests/tls_hooks/tls_hooks9.test.py b/tests/gold_tests/tls_hooks/tls_hooks9.test.py
index 6407a7bec6e..b934f29f55f 100644
--- a/tests/gold_tests/tls_hooks/tls_hooks9.test.py
+++ b/tests/gold_tests/tls_hooks/tls_hooks9.test.py
@@ -58,10 +58,10 @@
 tr.Processes.Default.ReturnCode = 0
 tr.Processes.Default.Streams.stdout = "gold/preaccept-1.gold"
 
-ts.Streams.stderr = "gold/ts-cert-im-1.gold"
+ts.Disk.traffic_out.Content = "gold/ts-cert-im-1.gold"
 
 certstring0 = "Cert callback 0"
-ts.Streams.All = Testers.ContainsExpression(
+ts.Disk.traffic_out.Content = Testers.ContainsExpression(
     "\A(?:(?!{0}).)*{0}(?!.*{0}).*\Z".format(certstring0), "Cert message appears only once", reflags=re.S | re.M)
 tr.Processes.Default.TimeOut = 15
 tr.TimeOut = 15