diff --git a/tests/test_bundler.py b/tests/test_bundler.py
index f7369e2..82a6a93 100644
--- a/tests/test_bundler.py
+++ b/tests/test_bundler.py
@@ -1,6 +1,18 @@
 # test_bundler.py
 """Unit tests for lta/bundler.py."""
 
+# -----------------------------------------------------------------------------
+# reset prometheus registry for unit tests
+from prometheus_client import REGISTRY
+collectors = list(REGISTRY._collector_to_names.keys())
+for collector in collectors:
+    REGISTRY.unregister(collector)
+from prometheus_client import gc_collector, platform_collector, process_collector
+process_collector.ProcessCollector()
+platform_collector.PlatformCollector()
+gc_collector.GCCollector()
+# -----------------------------------------------------------------------------
+
 import os
 from typing import Dict
 from unittest.mock import AsyncMock, call, mock_open, patch
diff --git a/tests/test_deleter.py b/tests/test_deleter.py
index 91403ed..f660218 100644
--- a/tests/test_deleter.py
+++ b/tests/test_deleter.py
@@ -1,6 +1,18 @@
 # test_deleter.py
 """Unit tests for lta/deleter.py."""
 
+# -----------------------------------------------------------------------------
+# reset prometheus registry for unit tests
+from prometheus_client import REGISTRY
+collectors = list(REGISTRY._collector_to_names.keys())
+for collector in collectors:
+    REGISTRY.unregister(collector)
+from prometheus_client import gc_collector, platform_collector, process_collector
+process_collector.ProcessCollector()
+platform_collector.PlatformCollector()
+gc_collector.GCCollector()
+# -----------------------------------------------------------------------------
+
 from typing import Dict
 from unittest.mock import AsyncMock, call, MagicMock
 
diff --git a/tests/test_desy_move_verifier.py b/tests/test_desy_move_verifier.py
index 0cd1ca9..7c13957 100644
--- a/tests/test_desy_move_verifier.py
+++ b/tests/test_desy_move_verifier.py
@@ -1,6 +1,18 @@
 # test_desy_move_verifier.py
 """Unit tests for lta/desy_move_verifier.py."""
 
+# -----------------------------------------------------------------------------
+# reset prometheus registry for unit tests
+from prometheus_client import REGISTRY
+collectors = list(REGISTRY._collector_to_names.keys())
+for collector in collectors:
+    REGISTRY.unregister(collector)
+from prometheus_client import gc_collector, platform_collector, process_collector
+process_collector.ProcessCollector()
+platform_collector.PlatformCollector()
+gc_collector.GCCollector()
+# -----------------------------------------------------------------------------
+
 from typing import Dict
 from unittest.mock import AsyncMock, call
 
diff --git a/tests/test_desy_verifier.py b/tests/test_desy_verifier.py
index a3a046a..8cfc1cf 100644
--- a/tests/test_desy_verifier.py
+++ b/tests/test_desy_verifier.py
@@ -1,6 +1,18 @@
 # test_desy_verifier.py
 """Unit tests for lta/desy_verifier.py."""
 
+# -----------------------------------------------------------------------------
+# reset prometheus registry for unit tests
+from prometheus_client import REGISTRY
+collectors = list(REGISTRY._collector_to_names.keys())
+for collector in collectors:
+    REGISTRY.unregister(collector)
+from prometheus_client import gc_collector, platform_collector, process_collector
+process_collector.ProcessCollector()
+platform_collector.PlatformCollector()
+gc_collector.GCCollector()
+# -----------------------------------------------------------------------------
+
 from typing import Dict
 from unittest.mock import AsyncMock, call
 from uuid import uuid1
diff --git a/tests/test_locator.py b/tests/test_locator.py
index a80dc41..1cf4fc3 100644
--- a/tests/test_locator.py
+++ b/tests/test_locator.py
@@ -1,6 +1,18 @@
 # test_locator.py
 """Unit tests for lta/locator.py."""
 
+# -----------------------------------------------------------------------------
+# reset prometheus registry for unit tests
+from prometheus_client import REGISTRY
+collectors = list(REGISTRY._collector_to_names.keys())
+for collector in collectors:
+    REGISTRY.unregister(collector)
+from prometheus_client import gc_collector, platform_collector, process_collector
+process_collector.ProcessCollector()
+platform_collector.PlatformCollector()
+gc_collector.GCCollector()
+# -----------------------------------------------------------------------------
+
 from math import floor
 from secrets import token_hex
 from typing import Any, Dict, List, Union
diff --git a/tests/test_nersc_mover.py b/tests/test_nersc_mover.py
index ceb80e3..6341c4f 100644
--- a/tests/test_nersc_mover.py
+++ b/tests/test_nersc_mover.py
@@ -1,6 +1,18 @@
 # test_nersc_mover.py
 """Unit tests for lta/nersc_mover.py."""
 
+# -----------------------------------------------------------------------------
+# reset prometheus registry for unit tests
+from prometheus_client import REGISTRY
+collectors = list(REGISTRY._collector_to_names.keys())
+for collector in collectors:
+    REGISTRY.unregister(collector)
+from prometheus_client import gc_collector, platform_collector, process_collector
+process_collector.ProcessCollector()
+platform_collector.PlatformCollector()
+gc_collector.GCCollector()
+# -----------------------------------------------------------------------------
+
 from typing import Dict
 from unittest.mock import AsyncMock, call, MagicMock
 
diff --git a/tests/test_nersc_retriever.py b/tests/test_nersc_retriever.py
index 795564f..8bc29ea 100644
--- a/tests/test_nersc_retriever.py
+++ b/tests/test_nersc_retriever.py
@@ -1,6 +1,18 @@
 # test_nersc_retriever.py
 """Unit tests for lta/nersc_retriever.py."""
 
+# -----------------------------------------------------------------------------
+# reset prometheus registry for unit tests
+from prometheus_client import REGISTRY
+collectors = list(REGISTRY._collector_to_names.keys())
+for collector in collectors:
+    REGISTRY.unregister(collector)
+from prometheus_client import gc_collector, platform_collector, process_collector
+process_collector.ProcessCollector()
+platform_collector.PlatformCollector()
+gc_collector.GCCollector()
+# -----------------------------------------------------------------------------
+
 from typing import Dict
 from unittest.mock import AsyncMock, call, MagicMock
 
diff --git a/tests/test_nersc_verifier.py b/tests/test_nersc_verifier.py
index e1b16fa..2f5763b 100644
--- a/tests/test_nersc_verifier.py
+++ b/tests/test_nersc_verifier.py
@@ -1,6 +1,18 @@
 # test_nersc_verifier.py
 """Unit tests for lta/nersc_verifier.py."""
 
+# -----------------------------------------------------------------------------
+# reset prometheus registry for unit tests
+from prometheus_client import REGISTRY
+collectors = list(REGISTRY._collector_to_names.keys())
+for collector in collectors:
+    REGISTRY.unregister(collector)
+from prometheus_client import gc_collector, platform_collector, process_collector
+process_collector.ProcessCollector()
+platform_collector.PlatformCollector()
+gc_collector.GCCollector()
+# -----------------------------------------------------------------------------
+
 from typing import Dict
 from unittest.mock import AsyncMock, call, MagicMock
 from uuid import uuid1
diff --git a/tests/test_picker.py b/tests/test_picker.py
index 6e3f64b..87d7092 100644
--- a/tests/test_picker.py
+++ b/tests/test_picker.py
@@ -1,6 +1,18 @@
 # test_picker.py
 """Unit tests for lta/picker.py."""
 
+# -----------------------------------------------------------------------------
+# reset prometheus registry for unit tests
+from prometheus_client import REGISTRY
+collectors = list(REGISTRY._collector_to_names.keys())
+for collector in collectors:
+    REGISTRY.unregister(collector)
+from prometheus_client import gc_collector, platform_collector, process_collector
+process_collector.ProcessCollector()
+platform_collector.PlatformCollector()
+gc_collector.GCCollector()
+# -----------------------------------------------------------------------------
+
 from secrets import token_hex
 from typing import Any, Dict, List, Union
 from unittest.mock import AsyncMock, call, MagicMock
diff --git a/tests/test_rate_limiter.py b/tests/test_rate_limiter.py
index c484082..74a1c45 100644
--- a/tests/test_rate_limiter.py
+++ b/tests/test_rate_limiter.py
@@ -1,6 +1,18 @@
 # test_rate_limiter.py
 """Unit tests for lta/rate_limiter.py."""
 
+# -----------------------------------------------------------------------------
+# reset prometheus registry for unit tests
+from prometheus_client import REGISTRY
+collectors = list(REGISTRY._collector_to_names.keys())
+for collector in collectors:
+    REGISTRY.unregister(collector)
+from prometheus_client import gc_collector, platform_collector, process_collector
+process_collector.ProcessCollector()
+platform_collector.PlatformCollector()
+gc_collector.GCCollector()
+# -----------------------------------------------------------------------------
+
 from typing import Dict
 from unittest.mock import AsyncMock, call, MagicMock
 
diff --git a/tests/test_site_move_verifier.py b/tests/test_site_move_verifier.py
index 5587e6f..af25bd2 100644
--- a/tests/test_site_move_verifier.py
+++ b/tests/test_site_move_verifier.py
@@ -1,6 +1,18 @@
 # test_site_move_verifier.py
 """Unit tests for lta/site_move_verifier.py."""
 
+# -----------------------------------------------------------------------------
+# reset prometheus registry for unit tests
+from prometheus_client import REGISTRY
+collectors = list(REGISTRY._collector_to_names.keys())
+for collector in collectors:
+    REGISTRY.unregister(collector)
+from prometheus_client import gc_collector, platform_collector, process_collector
+process_collector.ProcessCollector()
+platform_collector.PlatformCollector()
+gc_collector.GCCollector()
+# -----------------------------------------------------------------------------
+
 from typing import Dict
 from unittest.mock import AsyncMock, call, MagicMock
 
diff --git a/tests/test_transfer_request_finisher.py b/tests/test_transfer_request_finisher.py
index 4050e47..d0dbf22 100644
--- a/tests/test_transfer_request_finisher.py
+++ b/tests/test_transfer_request_finisher.py
@@ -1,6 +1,18 @@
 # test_transfer_request_finisher.py
 """Unit tests for lta/transfer_request_finisher.py."""
 
+# -----------------------------------------------------------------------------
+# reset prometheus registry for unit tests
+from prometheus_client import REGISTRY
+collectors = list(REGISTRY._collector_to_names.keys())
+for collector in collectors:
+    REGISTRY.unregister(collector)
+from prometheus_client import gc_collector, platform_collector, process_collector
+process_collector.ProcessCollector()
+platform_collector.PlatformCollector()
+gc_collector.GCCollector()
+# -----------------------------------------------------------------------------
+
 from typing import Dict
 from unittest.mock import AsyncMock, call
 
diff --git a/tests/test_unpacker.py b/tests/test_unpacker.py
index 75c7996..247fbe0 100644
--- a/tests/test_unpacker.py
+++ b/tests/test_unpacker.py
@@ -1,6 +1,18 @@
 # test_unpacker.py
 """Unit tests for lta/unpacker.py."""
 
+# -----------------------------------------------------------------------------
+# reset prometheus registry for unit tests
+from prometheus_client import REGISTRY
+collectors = list(REGISTRY._collector_to_names.keys())
+for collector in collectors:
+    REGISTRY.unregister(collector)
+from prometheus_client import gc_collector, platform_collector, process_collector
+process_collector.ProcessCollector()
+platform_collector.PlatformCollector()
+gc_collector.GCCollector()
+# -----------------------------------------------------------------------------
+
 from typing import Any, Dict
 from unittest.mock import AsyncMock, call, MagicMock, mock_open, patch