diff --git a/test/unit/data/model/test_mapping.py b/test/unit/data/model/test_mapping.py
index 6c4a765ca7b7..d29432075f30 100644
--- a/test/unit/data/model/test_mapping.py
+++ b/test/unit/data/model/test_mapping.py
@@ -67,6 +67,7 @@ def test_relationships(self, session, cls_, star, satellite):  # satellite is a
 import pytest
 from sqlalchemy import (
     delete,
+    func,
     select,
     UniqueConstraint,
 )
@@ -4537,6 +4538,8 @@ def test_columns(self, session, cls_):
             assert stored_obj.parent_id == parent_tag.id
             assert stored_obj.name == name
 
+        delete_from_database(session, parent_tag)
+
     def test_relationships(
         self,
         session,
@@ -4557,6 +4560,8 @@ def add_association(assoc_object, assoc_attribute):
             assert stored_obj.parent.id == parent_tag.id
             assert stored_obj.children == [child_tag]
 
+        delete_from_database(session, [parent_tag, child_tag])
+
 
 class TestTask(BaseTest):
 
@@ -4775,8 +4780,12 @@ def test_relationships(
         stored_workflow,
         stored_workflow_menu_entry_factory,
     ):
+        cleanup = []
+
         history1 = history_factory(deleted=False)
+        cleanup.append(history1)
         history2 = history_factory(deleted=True)
+        cleanup.append(history2)
 
         obj = cls_()
 
@@ -4796,14 +4805,24 @@ def test_relationships(
         obj.social_auth.append(user_authnz_token)
 
         _private_role = role_factory(name=obj.email)
+        cleanup.append(_private_role)
+
         private_user_role = user_role_association_factory(obj, _private_role)
+        cleanup.append(private_user_role)
+
         obj.roles.append(private_user_role)
 
         _non_private_role = role_factory(name='a')
+        cleanup.append(_non_private_role)
+
         non_private_user_role = user_role_association_factory(obj, _non_private_role)
+        cleanup.append(non_private_user_role)
+
         obj.roles.append(non_private_user_role)
 
         swme = stored_workflow_menu_entry_factory()
+        cleanup.append(swme)
+
         swme.stored_workflow = stored_workflow
         swme.user = obj
 
@@ -4835,7 +4854,7 @@ def test_relationships(
             assert stored_obj.non_private_roles == [non_private_user_role]
             assert stored_obj.stored_workflows == [stored_workflow]
 
-        delete_from_database(session, [history1, history2, swme, private_user_role, non_private_user_role])
+        delete_from_database(session, cleanup)
 
 
 class TestUserAction(BaseTest):
@@ -6386,6 +6405,25 @@ def test_relationships(self, session, cls_, workflow_step, tag, user):
 
 
 # Misc. helper fixtures.
+@pytest.fixture(autouse=True)
+def ensure_database_is_empty(session, model):
+    """
+    Auto-runs before each test and any unscoped fixtures, except session and model on
+    which it depends. Verifies that all model tables in the database are empty. This
+    ensures that a test is not affected by data leftover from a previous test run.
+    For fixture instantiation order, see:
+    https://docs.pytest.org/en/6.2.x/fixture.html#fixture-instantiation-order
+    """
+    # Created indirectrly (via db trigger and at Job instantiation): can't cleanup up automatically
+    exceptions = ['HistoryAudit', 'JobStateHistory']
+    models = (cls_ for cls_ in model.__dict__.values()
+        if hasattr(cls_, '__mapper__') and cls_.__name__ not in exceptions)
+    # For each mapped class, check that the database table to which it is mapped is empty
+    for m in models:
+        stmt = select(func.count()).select_from(m)
+        result = session.execute(stmt).scalar()
+        assert result == 0
+
 
 @pytest.fixture(scope='module')
 def model():