diff --git a/atst/domain/workspace_users.py b/atst/domain/workspace_users.py
index 9ff139cd..857be057 100644
--- a/atst/domain/workspace_users.py
+++ b/atst/domain/workspace_users.py
@@ -1,17 +1,23 @@
 from sqlalchemy.orm.exc import NoResultFound
 from sqlalchemy.dialects.postgresql import insert
 
-from atst.models import User, WorkspaceRole, Role
+from atst.models.workspace_role import WorkspaceRole
+from atst.models.workspace_user import WorkspaceUser
+from atst.models.user import User
+from .roles import Roles
+from .users import Users
 from .exceptions import NotFoundError
 
 class WorkspaceUsers(object):
 
     def __init__(self, db_session):
         self.db_session = db_session
+        self.roles_repo = Roles(db_session)
+        self.users_repo = Users(db_session)
 
     def get(self, workspace_id, user_id):
         try:
-            user = User.query.filter_by(id=user_id).one()
+            user = self.users_repo.get(user_id)
         except NoResultFound:
             raise NotFoundError("user")
 
@@ -31,18 +37,18 @@ class WorkspaceUsers(object):
 
         for user_dict in workspace_user_dicts:
             try:
-                user = User.query.filter_by(id=user_dict["id"]).one()
+                user = self.users_repo.get(user_dict["id"])
             except NoResultFound:
-                default_role = Role.query.filter_by(name="developer").one_or_none()
+                default_role = self.roles_repo.get("developer")
                 user = User(id=user_dict["id"], atat_role=default_role)
 
             try:
-                role = Role.query.filter_by(name=user_dict["workspace_role"]).one()
+                role = self.roles_repo.get(user_dict["workspace_role"])
             except NoResultFound:
                 raise NotFoundError("role")
 
             try:
-                existing_workspace_role = WorkspaceRole.query.filter(
+                existing_workspace_role = self.db_session.query(WorkspaceRole).filter(
                     WorkspaceRole.user == user,
                     WorkspaceRole.workspace_id == workspace_id,
                 ).one()
diff --git a/tests/domain/test_workspace_users.py b/tests/domain/test_workspace_users.py
new file mode 100644
index 00000000..e86662f3
--- /dev/null
+++ b/tests/domain/test_workspace_users.py
@@ -0,0 +1,43 @@
+import pytest
+from uuid import uuid4
+
+from atst.domain.workspace_users import WorkspaceUsers
+from atst.domain.users import Users
+
+
+@pytest.fixture()
+def users_repo(db):
+    return Users(db)
+
+@pytest.fixture()
+def workspace_users_repo(db):
+    return WorkspaceUsers(db)
+
+def test_can_create_new_workspace_user(users_repo, workspace_users_repo):
+    workspace_id = uuid4()
+    user = users_repo.create(uuid4(), "developer")
+
+    workspace_user_dicts = [
+        {"id": user.id, "workspace_role": "owner"}
+    ]
+
+    workspace_users = workspace_users_repo.add_many(workspace_id, workspace_user_dicts)
+
+    assert workspace_users[0].user.id == user.id
+    assert workspace_users[0].user.atat_role.name == "developer"
+    assert workspace_users[0].workspace_role.role.name == "owner"
+
+
+def test_can_update_existing_workspace_user(users_repo, workspace_users_repo):
+    workspace_id = uuid4()
+    user = users_repo.create(uuid4(), "developer")
+
+    workspace_users_repo.add_many(workspace_id, [
+        {"id": user.id, "workspace_role": "owner"}
+    ])
+    workspace_users = workspace_users_repo.add_many(workspace_id, [
+        {"id": user.id, "workspace_role": "developer"}
+    ])
+
+    assert workspace_users[0].user.id == user.id
+    assert workspace_users[0].workspace_role.role.name == "developer"