diff --git a/api/group.py b/api/group.py
index 02cb03727..d1df69f1c 100644
--- a/api/group.py
+++ b/api/group.py
@@ -15,7 +15,7 @@
 # ===============================================================================
 
 from fastapi import Depends, APIRouter, Query
-from starlette import status
+from starlette.status import HTTP_201_CREATED, HTTP_204_NO_CONTENT
 
 from api.pagination import CustomPage
 from core.dependencies import (
@@ -25,10 +25,9 @@
     viewer_function,
 )
 from db import adder
-from db.group import Group, GroupThingAssociation
+from db.group import Group
 from schemas.group import UpdateGroup, CreateGroup, GroupResponse
-from schemas.location import CreateGroupThing
-from services.crud_helper import model_patcher
+from services.crud_helper import model_patcher, model_deleter
 from services.query_helper import (
     simple_get_by_id,
     paginated_all_getter,
@@ -38,8 +37,10 @@
     prefix="/group", tags=["group"], dependencies=[Depends(viewer_function)]
 )
 
+# POST =========================================================================
 
-@router.post("", summary="Create a new group", status_code=status.HTTP_201_CREATED)
+
+@router.post("", summary="Create a new group", status_code=HTTP_201_CREATED)
 def create_group(
     group_data: CreateGroup, session: session_dependency, user: admin_dependency
 ) -> GroupResponse:
@@ -110,4 +111,14 @@ async def update_group(
     return model_patcher(session, Group, group_id, group_data, user=user)
 
 
+# DELETE =======================================================================
+@router.delete(
+    "/{group_id}", summary="Delete a group by ID", status_code=HTTP_204_NO_CONTENT
+)
+async def delete_group(
+    user: admin_dependency, group_id: int, session: session_dependency
+):
+    return model_deleter(session, Group, group_id)
+
+
 # ============= EOF =============================================
diff --git a/api/location.py b/api/location.py
index 666e09fe3..3352168ae 100644
--- a/api/location.py
+++ b/api/location.py
@@ -13,17 +13,20 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 # ===============================================================================
-from fastapi import Depends, Query, Response
+from fastapi import Query, Response
 from fastapi_pagination.ext.sqlalchemy import paginate
 from sqlalchemy import select, func
-from sqlalchemy.orm import Session
 from starlette import status
 from api.pagination import CustomPage
 from constants import SRID_WGS84
-from core.dependencies import session_dependency
+from core.dependencies import (
+    session_dependency,
+    admin_dependency,
+    editor_dependency,
+    viewer_dependency,
+)
 from db import adder
 from db.location import Location
-from db.engine import get_db_session
 from schemas.location import CreateLocation, LocationResponse, UpdateLocation
 from services.geospatial_helper import make_within_wkt
 from services.query_helper import make_query, order_sort_filter, simple_get_by_id
@@ -41,12 +44,12 @@
     status_code=status.HTTP_201_CREATED,
 )
 def create_location(
-    location_data: CreateLocation, session: Session = Depends(get_db_session)
+    location_data: CreateLocation, session: session_dependency, user: admin_dependency
 ) -> LocationResponse:
     """
     Create a new sample location in the database.
     """
-    return adder(session, Location, location_data)
+    return adder(session, Location, location_data, user=user)
 
 
 @router.patch(
@@ -56,12 +59,13 @@ def create_location(
 def update_location(
     location_id: int,
     location_data: UpdateLocation,
-    session: Session = Depends(get_db_session),
+    session: session_dependency,
+    user: editor_dependency,
 ) -> LocationResponse:
     """
     Update a sample location in the database.
     """
-    return model_patcher(session, Location, location_id, location_data)
+    return model_patcher(session, Location, location_id, location_data, user=user)
 
 
 # @router.get("/shapefile", summary="Get location as shapefile")
@@ -125,6 +129,7 @@ def update_location(
 )
 async def get_location(
     session: session_dependency,
+    user: viewer_dependency,
     nearby_point: str = None,
     nearby_distance_km: float = 1,
     within: str = None,
@@ -160,7 +165,7 @@ async def get_location(
     summary="Get location by ID",
 )
 async def get_location_by_id(
-    location_id: int, session: Session = Depends(get_db_session)
+    location_id: int, session: session_dependency, user: viewer_dependency
 ) -> LocationResponse:
     """
     Retrieve a sample location by ID from the database.
@@ -171,7 +176,7 @@ async def get_location_by_id(
 
 @router.delete("/{location_id}", summary="Delete location by ID")
 async def delete_location(
-    location_id: int, session: Session = Depends(get_db_session)
+    location_id: int, session: session_dependency, user: admin_dependency
 ) -> Response:
     """
     Delete a sample location by ID from the database.
diff --git a/api/sample.py b/api/sample.py
index 9a3755093..c9107237c 100644
--- a/api/sample.py
+++ b/api/sample.py
@@ -14,15 +14,18 @@
 # limitations under the License.
 # ===============================================================================
 
-from fastapi import APIRouter, Depends, Query, Response
+from fastapi import APIRouter, Query, Response
 from sqlalchemy.exc import IntegrityError, ProgrammingError
-from sqlalchemy.orm import Session
 from starlette.status import HTTP_201_CREATED, HTTP_409_CONFLICT
 
 from api.pagination import CustomPage
-from core.dependencies import session_dependency
+from core.dependencies import (
+    session_dependency,
+    admin_dependency,
+    editor_dependency,
+    viewer_dependency,
+)
 from db import adder
-from db.engine import get_db_session
 from db.sample import Sample
 from schemas import ResourceNotFoundResponse
 from schemas.sample import SampleResponse, CreateSample, UpdateSample
@@ -70,13 +73,13 @@ def database_error_handler(
 # ============= Post =============================================
 @router.post("", status_code=HTTP_201_CREATED)
 def add_sample(
-    sample_data: CreateSample, session: session_dependency
+    sample_data: CreateSample, session: session_dependency, user: admin_dependency
 ) -> SampleResponse:
     """
     Endpoint to add a sample.
     """
     try:
-        return adder(session, Sample, sample_data)
+        return adder(session, Sample, sample_data, user=user)
     except (IntegrityError, ProgrammingError) as e:
         database_error_handler(sample_data, e)
 
@@ -86,7 +89,8 @@ def add_sample(
 def update_sample(
     sample_id: int,
     sample_data: UpdateSample,
-    session: Session = Depends(get_db_session),
+    session: session_dependency,
+    user: editor_dependency,
 ) -> SampleResponse | ResourceNotFoundResponse:
     """
     Endpoint to update a sample.
@@ -105,7 +109,7 @@ def update_sample(
     the update.
     """
     try:
-        return model_patcher(session, Sample, sample_id, sample_data)
+        return model_patcher(session, Sample, sample_id, sample_data, user=user)
     except (IntegrityError, ProgrammingError) as e:
         database_error_handler(sample_data, e)
 
@@ -114,6 +118,7 @@ def update_sample(
 @router.get("", summary="Get Samples")
 def get_samples(
     session: session_dependency,
+    user: viewer_dependency,
     sort: str = None,
     order: str = None,
     filter_: str = Query(alias="filter", default=None),
@@ -129,7 +134,7 @@ def get_samples(
 
 @router.get("/{sample_id}", summary="Get Sample by ID")
 def get_sample_by_id(
-    sample_id: int, session: session_dependency
+    sample_id: int, session: session_dependency, user: viewer_dependency
 ) -> SampleResponse | ResourceNotFoundResponse:
     """
     Endpoint to retrieve a sample by its ID.
@@ -141,7 +146,9 @@ def get_sample_by_id(
 
 
 @router.delete("/{sample_id}", summary="Delete Sample by ID")
-def delete_sample_by_id(sample_id: int, session: session_dependency) -> Response:
+def delete_sample_by_id(
+    sample_id: int, session: session_dependency, user: admin_dependency
+) -> Response:
     return model_deleter(session, Sample, sample_id)
 
 
diff --git a/api/sensor.py b/api/sensor.py
index bb92c4232..5239f3175 100644
--- a/api/sensor.py
+++ b/api/sensor.py
@@ -20,7 +20,12 @@
 from starlette import status
 
 from api.pagination import CustomPage
-from core.dependencies import session_dependency
+from core.dependencies import (
+    session_dependency,
+    admin_dependency,
+    editor_dependency,
+    viewer_dependency,
+)
 from db import adder, Observation, Sample
 from db.sensor import Sensor
 from schemas.sensor import SensorResponse, CreateSensor, UpdateSensor
@@ -35,12 +40,12 @@
 
 @router.post("", status_code=status.HTTP_201_CREATED)
 def add_sensor(
-    sensor_data: CreateSensor, session: session_dependency
+    sensor_data: CreateSensor, session: session_dependency, user: admin_dependency
 ) -> SensorResponse:
     """
     Add a sensor to the system.
     """
-    return adder(session, Sensor, sensor_data)
+    return adder(session, Sensor, sensor_data, user=user)
 
 
 # ====== PATCH =================================================================
@@ -48,7 +53,10 @@ def add_sensor(
 
 @router.patch("/{sensor_id}", status_code=status.HTTP_200_OK)
 def update_sensor(
-    sensor_id: int, sensor_data: UpdateSensor, session: session_dependency
+    sensor_id: int,
+    sensor_data: UpdateSensor,
+    session: session_dependency,
+    user: editor_dependency,
 ) -> SensorResponse:
     """
     Update a sensor in the system.
@@ -97,14 +105,16 @@ def update_sensor(
                 status_code=status.HTTP_409_CONFLICT, detail=[detail]
             )
 
-    return model_patcher(session, Sensor, sensor_id, sensor_data)
+    return model_patcher(session, Sensor, sensor_id, sensor_data, user=user)
 
 
 # ====== DELETE ================================================================
 
 
 @router.delete("/{sensor_id}")
-def delete_sensor(sensor_id: int, session: session_dependency) -> Response:
+def delete_sensor(
+    sensor_id: int, session: session_dependency, user: admin_dependency
+) -> Response:
     """
     Delete a sensor in the system
     """
@@ -117,6 +127,7 @@ def delete_sensor(sensor_id: int, session: session_dependency) -> Response:
 @router.get("", status_code=status.HTTP_200_OK)
 def get_sensors(
     session: session_dependency,
+    user: viewer_dependency,
     thing_id: int = None,  # Optional filter for thing_id
     observed_property: str = None,  # Optional filter for observed_property
     sort: str | None = None,
@@ -151,7 +162,9 @@ def get_sensors(
 
 
 @router.get("/{sensor_id}", status_code=status.HTTP_200_OK)
-def get_sensor(sensor_id: int, session: session_dependency) -> SensorResponse:
+def get_sensor(
+    sensor_id: int, session: session_dependency, user: viewer_dependency
+) -> SensorResponse:
     """
     Retrieve a sensor by its ID.
     """
diff --git a/schemas/group.py b/schemas/group.py
index f61282331..c5f525748 100644
--- a/schemas/group.py
+++ b/schemas/group.py
@@ -15,7 +15,8 @@
 # ===============================================================================
 from geoalchemy2 import WKBElement
 from geoalchemy2.shape import to_shape
-from pydantic import BaseModel, field_validator
+from pydantic import BaseModel, field_validator, model_validator
+from typing_extensions import Self
 
 from schemas import ORMBaseModel
 from services.validation.geospatial import validate_wkt_geometry
@@ -23,14 +24,16 @@
 
 class ValidateGroup(BaseModel):
     project_area: str | None = None
-
     description: str | None = None
     parent_group_id: int | None = None
 
-    @classmethod
     @field_validator("project_area")
     def validate_area_is_wkt(cls, wkt):
-        return validate_wkt_geometry(wkt)
+        valid_wkt = validate_wkt_geometry(wkt)
+        if "MULTIPOLYGON" not in valid_wkt:
+            raise ValueError("WKT must be a valid MULTIPOLYGON")
+
+        return valid_wkt
 
 
 # -------- CREATE ----------
@@ -49,25 +52,16 @@ class GroupResponse(ORMBaseModel):
     This model can be extended to include additional fields as needed.
     """
 
-    id: int
     name: str
-    description: str | None = None
-    parent_group_id: int | None = None
-
-    @classmethod
-    @field_validator("project_area", mode="before")
-    def project_area_to_wkt(cls, value):
-        if not value:
-            return value
-
-        if isinstance(value, WKBElement):
-            return to_shape(value).wkt
-
-        # If the value is a string, assume it's already in WKT format
-        if isinstance(value, str):
-            return value
-
-        return None
+    project_area: str | None
+    description: str | None
+    parent_group_id: int | None
+
+    @model_validator(mode="before")
+    def project_area_to_wkt(self: Self) -> Self:
+        if isinstance(self.project_area, WKBElement):
+            self.project_area = to_shape(self.project_area).wkt
+        return self
 
 
 # -------- UPDATE ----------
diff --git a/tests/conftest.py b/tests/conftest.py
index 0fc57fb1f..db72abf53 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -18,6 +18,21 @@ def location():
         session.close()
 
 
+@pytest.fixture(scope="function")
+def second_location():
+    with session_ctx() as session:
+        location = Location(
+            name="second location",
+            point="POINT (10.2 10.2)",
+            release_status="draft",
+        )
+        session.add(location)
+        session.commit()
+        yield location
+        session.delete(location)
+        session.commit()
+
+
 @pytest.fixture(scope="session")
 def thing(location):
     with session_ctx() as session:
@@ -53,6 +68,26 @@ def sensor():
         session.close()
 
 
+@pytest.fixture(scope="function")
+def second_sensor():
+    with session_ctx() as session:
+        sensor = Sensor(
+            name="Test Sensor 2",
+            model="Model X",
+            serial_no="123456",
+            datetime_installed="2023-01-01T00:00:00Z",
+            datetime_removed="2023-01-02T00:00:00Z",
+            recording_interval=60,
+            notes="Test equipment",
+        )
+        session.add(sensor)
+        session.commit()
+        yield sensor
+        session.delete(sensor)
+        session.commit()
+        session.close()
+
+
 @pytest.fixture(scope="session")
 def sample(thing, sensor):
     with session_ctx() as session:
@@ -78,6 +113,32 @@ def sample(thing, sensor):
         session.close()
 
 
+@pytest.fixture(scope="function")
+def second_sample(thing, sensor):
+    with session_ctx() as session:
+        sample = Sample(
+            thing_id=thing.id,
+            sample_type="groundwater",
+            field_sample_id="FS-9999999",
+            sample_date="2025-01-01T00:00:00Z",
+            release_status="draft",
+            sampler_name="Test Sampler",
+            qc_sample="Duplicate",
+            sensor_id=sensor.id,
+            sample_matrix="water",
+            sample_method="manual",
+            duplicate_sample_number=3,
+            sample_top=2,
+            sample_bottom=3,
+        )
+        session.add(sample)
+        session.commit()
+        yield sample
+        session.delete(sample)
+        session.commit()
+        session.close()
+
+
 @pytest.fixture(scope="session")
 def contact(thing):
     with session_ctx() as session:
@@ -148,6 +209,80 @@ def phone(contact):
         session.close()
 
 
+@pytest.fixture(scope="function")
+def second_contact():
+    with session_ctx() as session:
+        contact = Contact(
+            name="Test Second Contact",
+            role="Owner",
+        )
+        session.add(contact)
+        session.commit()
+        session.refresh(contact)
+
+        yield contact
+
+        session.delete(contact)
+        session.commit()
+        session.close()
+
+
+@pytest.fixture(scope="function")
+def second_email(second_contact):
+    with session_ctx() as session:
+        email = Email(
+            email="testsecondcontact@gmail.com",
+            email_type="Primary",
+            contact_id=second_contact.id,
+        )
+        session.add(email)
+        session.commit()
+        session.refresh(email)
+        yield email
+        session.delete(email)
+        session.commit()
+        session.close()
+
+
+@pytest.fixture(scope="function")
+def second_phone(second_contact):
+    with session_ctx() as session:
+        phone = Phone(
+            phone_number="123-456-7890",
+            phone_type="Primary",
+            contact_id=second_contact.id,
+        )
+        session.add(phone)
+        session.commit()
+        session.refresh(phone)
+        yield phone
+        session.delete(phone)
+        session.commit()
+        session.close()
+
+
+@pytest.fixture(scope="function")
+def second_address(second_contact):
+    with session_ctx() as session:
+        address = Address(
+            address_line_1="456 Secondary St",
+            address_line_2="Apt 12A",
+            city="Test Metropolis",
+            state="NM",
+            postal_code="87501",
+            country="United States",
+            address_type="Primary",
+            contact_id=second_contact.id,
+        )
+        session.add(address)
+        session.commit()
+        session.refresh(address)
+        yield address
+        session.delete(address)
+        session.commit()
+        session.close()
+
+
 @pytest.fixture(scope="session")
 def asset():
     with session_ctx() as session:
@@ -274,3 +409,70 @@ def geothermal_observation(sensor, sample):
         yield observation
 
         session.close()
+
+
+@pytest.fixture(scope="function")
+def observation_to_delete(sample, sensor):
+    with session_ctx() as session:
+        observation = Observation(
+            observation_datetime="2019-01-01T00:03:00Z",
+            sample_id=sample.id,
+            sensor_id=sensor.id,
+            observed_property="water chemistry:pH",
+            release_status="draft",
+            value=4.0,
+            unit="dimensionless",
+        )
+        session.add(observation)
+        session.commit()
+        yield observation
+
+
+@pytest.fixture(scope="session")
+def group(thing):
+    with session_ctx() as session:
+        group = Group(
+            name="Test Group",
+            description="This is a test group.",
+            project_area="MULTIPOLYGON(((-107.2 33.6, -106.6 33.6, -106.6 34.2, -107.2 34.2, -107.2 33.6)))",
+        )
+
+        session.add(group)
+        session.commit()
+        session.refresh(group)
+
+        group_thing_association = GroupThingAssociation(
+            group_id=group.id, thing_id=thing.id
+        )
+        session.add(group_thing_association)
+        session.commit()
+        session.refresh(group_thing_association)
+
+        yield group
+
+        session.close()
+
+
+@pytest.fixture(scope="function")
+def second_group(thing):
+    with session_ctx() as session:
+        group = Group(
+            name="Second Test Group",
+            description="This is a second test group.",
+            project_area="MULTIPOLYGON(((-107.2 33.6, -106.6 33.6, -106.6 34.2, 0 0, -107.2 34.2, -107.2 33.6)))",
+        )
+
+        session.add(group)
+        session.commit()
+        session.refresh(group)
+
+        group_thing_association = GroupThingAssociation(
+            group_id=group.id, thing_id=thing.id
+        )
+        session.add(group_thing_association)
+        session.commit()
+        session.refresh(group_thing_association)
+
+        yield group
+
+        session.close()
diff --git a/tests/test_contact.py b/tests/test_contact.py
index dd80ffea6..19ec570e4 100644
--- a/tests/test_contact.py
+++ b/tests/test_contact.py
@@ -4,7 +4,6 @@
     amp_admin_function,
 )
 from db import Contact, Address, Email, Phone
-from db.engine import session_ctx
 from main import app
 from tests import client, cleanup_post_test, cleanup_patch_test, override_authentication
 from schemas.contact import ValidateEmail, ValidatePhone
@@ -30,98 +29,6 @@ def override_authentication_dependency_fixture():
     app.dependency_overrides = {}
 
 
-# ============= module & function fixtures =======================================
-
-
-@pytest.fixture(scope="function")
-def second_contact():
-    with session_ctx() as session:
-        contact = Contact(
-            name="Test Second Contact",
-            role="Owner",
-        )
-        session.add(contact)
-        session.commit()
-        session.refresh(contact)
-
-        yield contact
-
-        session.delete(contact)
-        session.commit()
-        session.close()
-
-
-@pytest.fixture(scope="function")
-def second_email(second_contact):
-    with session_ctx() as session:
-        email = Email(
-            email="testsecondcontact@gmail.com",
-            email_type="Primary",
-            contact_id=second_contact.id,
-        )
-        session.add(email)
-        session.commit()
-        session.refresh(email)
-        yield email
-        session.delete(email)
-        session.commit()
-        session.close()
-
-
-@pytest.fixture(scope="function")
-def second_phone(second_contact):
-    with session_ctx() as session:
-        phone = Phone(
-            phone_number="123-456-7890",
-            phone_type="Primary",
-            contact_id=second_contact.id,
-        )
-        session.add(phone)
-        session.commit()
-        session.refresh(phone)
-        yield phone
-        session.delete(phone)
-        session.commit()
-        session.close()
-
-
-@pytest.fixture(scope="function")
-def second_address(second_contact):
-    with session_ctx() as session:
-        address = Address(
-            address_line_1="456 Secondary St",
-            address_line_2="Apt 12A",
-            city="Test Metropolis",
-            state="NM",
-            postal_code="87501",
-            country="United States",
-            address_type="Primary",
-            contact_id=second_contact.id,
-        )
-        session.add(address)
-        session.commit()
-        session.refresh(address)
-        yield address
-        session.delete(address)
-        session.commit()
-        session.close()
-
-
-# @pytest.fixture(scope="function")
-# def second_thing_contact_association(thing, second_contact):
-#     with session_ctx() as session:
-#         association = ThingContactAssociation(
-#             thing_id=thing.id, contact_id=second_contact.id
-#         )
-#         session.add(association)
-#         session.commit()
-#         session.refresh(association)
-#         yield association
-#         session.delete(association)
-#         session.commit()
-#         session.close()
-
-
 # VALIDATION tests =============================================================
 
 
diff --git a/tests/test_group.py b/tests/test_group.py
index e652339a7..4b9095591 100644
--- a/tests/test_group.py
+++ b/tests/test_group.py
@@ -1,8 +1,12 @@
+from geoalchemy2.shape import to_shape
+from pydantic import ValidationError
 import pytest
 
+from db import Group
 from core.dependencies import admin_function, viewer_function, editor_function
 from main import app
-from tests import client, override_authentication
+from schemas.group import ValidateGroup
+from tests import client, override_authentication, cleanup_post_test, cleanup_patch_test
 
 
 @pytest.fixture(scope="module", autouse=True)
@@ -21,82 +25,144 @@ def override_authentication_dependency_fixture():
     app.dependency_overrides = {}
 
 
+# VALIDATION tests =============================================================
+
+
+def test_project_area_not_topologically_valid():
+    wkt = "MULTIPOLYGON(((0 0, 1 1, 2 2, 0 0)))"
+    with pytest.raises(
+        ValidationError, match="WKT geometry is not topologically valid"
+    ):
+        ValidateGroup(project_area=wkt)
+
+
+def test_project_area_invalid_wkt():
+    for wkt in [
+        "MULTIPOLYGON((0 0, 1 1, 2 2, 0 0))",
+        "0 0, 1 1, 2 2, 3 3, 4 5, 0 0",
+    ]:
+        with pytest.raises(ValidationError, match=r"Invalid WKT geometry: "):
+            ValidateGroup(project_area=wkt)
+
+
+def test_project_area_not_multipolygon():
+    for wkt in [
+        "POINT (0 0)",
+        "LINESTRING (0 0, 1 1, 2 2, 3 3)",
+        "POLYGON ((0 0, 1 1, 2 2, 1 2, 0 0))",
+    ]:
+        with pytest.raises(ValidationError, match="WKT must be a valid MULTIPOLYGON"):
+            ValidateGroup(project_area=wkt)
+
+
 #  ADD tests ======================================================
 
 
 def test_add_group():
-    response = client.post("/group", json={"name": "Test Group"})
+    payload = {
+        "name": "Test Group",
+        "description": "This is a test group.",
+        "project_area": "MULTIPOLYGON (((0 0, 1 1, 2 2, 3 3, 4 4, 1 2, 0 0)))",
+    }
+    response = client.post("/group", json=payload)
     assert response.status_code == 201
     data = response.json()
     assert "id" in data
-    assert data["name"] == "Test Group"
+    assert "created_at" in data
+    assert data["name"] == payload["name"]
+    assert data["description"] == payload["description"]
+    assert data["project_area"] == payload["project_area"]
 
-
-def test_add_group_with_area():
-    response = client.post(
-        "/group",
-        json={
-            "name": "Test Group with Project Area",
-            "project_area": "MULTIPOLYGON(((-107.2 33.6, -106.6 33.6, -106.6 34.2, -107.2 34.2, -107.2 33.6)))",
-        },
-    )
-    assert response.status_code == 201
-    data = response.json()
-
-
-# def test_add_group_thing(location, thing):
-#     response = client.post(
-#         "/group/association", json={"group_id": 2, "thing_id": thing.id}
-#     )
-#     assert response.status_code == 201
-#
-#     data = response.json()
-#     assert "id" in data
-#     assert data["group_id"] == 2
-#     assert data["thing_id"] == thing.id
+    cleanup_post_test(Group, data["id"])
 
 
 # GET tests ======================================================
 
 
-def test_get_groups():
+def test_get_groups(group):
     response = client.get("/group")
     assert response.status_code == 200
-    assert len(response.json()) > 0
+    data = response.json()
+    assert data["total"] == 1
+    assert data["items"][0]["id"] == group.id
+    assert data["items"][0]["created_at"] == group.created_at.isoformat().replace(
+        "+00:00", "Z"
+    )
+    assert data["items"][0]["name"] == group.name
+    assert data["items"][0]["project_area"] == to_shape(group.project_area).wkt
+    assert data["items"][0]["description"] == group.description
+    assert data["items"][0]["parent_group_id"] == group.parent_group_id
 
 
-@pytest.mark.skip
+def test_get_group_by_id(group):
+    response = client.get(f"/group/{group.id}")
+    assert response.status_code == 200
+    data = response.json()
+    assert data["id"] == group.id
+    assert data["created_at"] == group.created_at.isoformat().replace("+00:00", "Z")
+    assert data["name"] == group.name
+    assert data["project_area"] == to_shape(group.project_area).wkt
+    assert data["description"] == group.description
+    assert data["parent_group_id"] == group.parent_group_id
+
+
+def test_get_group_by_id_404_not_found(group):
+    bad_id = 99999
+    response = client.get(f"/group/{bad_id}")
+    assert response.status_code == 404
+    data = response.json()
+    assert data["detail"] == f"Group with ID {bad_id} not found."
+
+
+@pytest.mark.skip("associations not yet implemented")
 def test_get_group_things():
     response = client.get("/group/association")
     assert response.status_code == 200
     assert len(response.json()) > 0
 
 
-# test item retrieval via filter ===========================================
+# PATCH tests ==================================================================
 
 
-# Test item retrieval ======================================================
-# @pytest.mark.skip
-# def test_item_get_spring():
-#     response = client.get("/thing/spring/1")
-#     assert response.status_code == 200
-#     data = response.json()
-#     assert data["id"] == 1
-#     assert data["location_id"] == 1
+def test_patch_group(group):
+    payload = {
+        "name": "Updated Group",
+    }
+    response = client.patch(f"/group/{group.id}", json=payload)
+    assert response.status_code == 200
+    data = response.json()
+    assert data["id"] == group.id
+    assert data["name"] == payload["name"]
 
+    cleanup_patch_test(Group, payload, group)
 
-def test_item_get_group():
-    response = client.get("/group/2")
-    assert response.status_code == 200
+
+def test_patch_group_404_not_found(group):
+    payload = {"name": "Failed group patch"}
+    bad_id = 99999
+    response = client.patch(f"/group/{bad_id}", json=payload)
+    assert response.status_code == 404
+    data = response.json()
+    assert data["detail"] == f"Group with ID {bad_id} not found."
+
+
+# DELETE tests =================================================================
+
+
+def test_delete_group(second_group):
+    response = client.delete(f"/group/{second_group.id}")
+    assert response.status_code == 204
+
+    # verify deletion
+    response = client.get(f"/group/{second_group.id}")
+    assert response.status_code == 404
     data = response.json()
-    assert data["id"] == 2
-    assert data["name"] == "Test Group"
+    assert data["detail"] == f"Group with ID {second_group.id} not found."
 
 
-# def test_item_get_group_thing(location, thing):
-#     response = client.get("/group/association/1")
-#     assert response.status_code == 200
-#     data = response.json()
-#     assert data["id"] == 1
-#     assert data["group_id"] == 2
-#     assert data["thing_id"] == thing.id
+def test_delete_group_404_not_found(second_group):
+    bad_id = 99999
+    response = client.delete(f"/group/{bad_id}")
+    assert response.status_code == 404
+    data = response.json()
+    assert data["detail"] == f"Group with ID {bad_id} not found."
diff --git a/tests/test_location.py b/tests/test_location.py
index ee98770d1..cee06ab2b 100644
--- a/tests/test_location.py
+++ b/tests/test_location.py
@@ -16,26 +16,25 @@
 from geoalchemy2.shape import to_shape
 import pytest
 
+from core.dependencies import admin_function, editor_function, viewer_function
 from db import Location
-from db.engine import session_ctx
-from tests import client
+from main import app
+from tests import client, override_authentication, cleanup_post_test, cleanup_patch_test
 
-# ============= module & function fixtures =======================================
 
+@pytest.fixture(scope="module", autouse=True)
+def override_dependencies_fixture():
+    app.dependency_overrides[admin_function] = override_authentication(
+        default={"name": "foobar", "sub": "1234567890"}
+    )
+    app.dependency_overrides[editor_function] = override_authentication(
+        default={"name": "foobar", "sub": "1234567890"}
+    )
+    app.dependency_overrides[viewer_function] = override_authentication()
 
-@pytest.fixture(scope="function")
-def second_location():
-    with session_ctx() as session:
-        location = Location(
-            name="second location",
-            point="POINT (10.2 10.2)",
-            release_status="draft",
-        )
-        session.add(location)
-        session.commit()
-        yield location
-        session.delete(location)
-        session.commit()
+    yield
+
+    app.dependency_overrides = {}
 
 
 #  ============= Post tests for locations ======================================
@@ -57,35 +56,23 @@ def test_add_location():
     assert data["release_status"] == payload["release_status"]
 
     # cleanup after test
-    with session_ctx() as session:
-        session.delete(session.get(Location, data["id"]))
-        session.commit()
+    cleanup_post_test(Location, data["id"])
 
 
 #  ============= Patch tests for locations =====================================
 
 
 def test_update_location(location):
-    location_id = location.id
-    response = client.patch(
-        f"/location/{location_id}",
-        json={
-            "point": "POINT (10.1 20.2)",
-            "release_status": "draft",
-        },
-    )
+    payload = {"point": "POINT (10.1 20.2)", "release_status": "draft"}
+    response = client.patch(f"/location/{location.id}", json=payload)
     assert response.status_code == 200
     data = response.json()
-    assert data["id"] == location_id
-    assert data["point"] == "POINT (10.1 20.2)"
-    assert data["release_status"] == "draft"
+    assert data["id"] == location.id
+    assert data["point"] == payload["point"]
+    assert data["release_status"] == payload["release_status"]
 
     # cleanup after test
-    with session_ctx() as session:
-        updated_location = session.get(Location, location_id)
-        updated_location.point = location.point
-        updated_location.release_status = location.release_status
-        session.commit()
+    cleanup_patch_test(Location, payload, location)
 
 
 def test_patch_location_404_not_found(location):
diff --git a/tests/test_observation.py b/tests/test_observation.py
index f1c94483c..6dcfc85de 100644
--- a/tests/test_observation.py
+++ b/tests/test_observation.py
@@ -14,7 +14,6 @@
 # limitations under the License.
 # ===============================================================================
 from db import Observation
-from db.engine import session_ctx
 from core.dependencies import (
     amp_admin_function,
     admin_function,
@@ -42,23 +41,6 @@ def override_authentication_dependency_fixture():
     app.dependency_overrides = {}
 
 
-@pytest.fixture(scope="function")
-def observation_to_delete(sample, sensor):
-    with session_ctx() as session:
-        observation = Observation(
-            observation_datetime="2019-01-01T00:03:00Z",
-            sample_id=sample.id,
-            sensor_id=sensor.id,
-            observed_property="water chemistry:pH",
-            release_status="draft",
-            value=4.0,
-            unit="dimensionless",
-        )
-        session.add(observation)
-        session.commit()
-        yield observation
-
-
 # ============= Post tests =================
 def test_add_water_chemistry_observation(sample, sensor):
     payload = {
diff --git a/tests/test_sample.py b/tests/test_sample.py
index 6004a60ed..d3d432413 100644
--- a/tests/test_sample.py
+++ b/tests/test_sample.py
@@ -16,38 +16,26 @@
 import pytest
 from pydantic import ValidationError
 
-from db.engine import session_ctx
+from main import app
+from core.dependencies import admin_function, editor_function, viewer_function
 from db.sample import Sample
 from schemas.sample import ValidateSample
-from tests import client
-
-# ============= module & function fixtures =======================================
-
-
-@pytest.fixture(scope="function")
-def second_sample(thing, sensor):
-    with session_ctx() as session:
-        sample = Sample(
-            thing_id=thing.id,
-            sample_type="groundwater",
-            field_sample_id="FS-9999999",
-            sample_date="2025-01-01T00:00:00Z",
-            release_status="draft",
-            sampler_name="Test Sampler",
-            qc_sample="Duplicate",
-            sensor_id=sensor.id,
-            sample_matrix="water",
-            sample_method="manual",
-            duplicate_sample_number=3,
-            sample_top=2,
-            sample_bottom=3,
-        )
-        session.add(sample)
-        session.commit()
-        yield sample
-        session.delete(sample)
-        session.commit()
-        session.close()
+from tests import client, cleanup_post_test, cleanup_patch_test, override_authentication
+
+
+@pytest.fixture(scope="module", autouse=True)
+def override_dependencies_fixture():
+    app.dependency_overrides[admin_function] = override_authentication(
+        default={"name": "foobar", "sub": "1234567890"}
+    )
+    app.dependency_overrides[editor_function] = override_authentication(
+        default={"name": "foobar", "sub": "1234567890"}
+    )
+    app.dependency_overrides[viewer_function] = override_authentication()
+
+    yield
+
+    app.dependency_overrides = {}
 
 
 # ============== Custom validators =================================================
@@ -105,9 +93,7 @@ def test_add_sample(thing, sensor):
     assert data["sample_bottom"] == payload["sample_bottom"]
 
     # cleanup after adding the sample
-    with session_ctx() as session:
-        session.delete(session.get(Sample, data["id"]))
-        session.commit()
+    cleanup_post_test(Sample, data["id"])
 
 
 def test_409_add_sample_invalid_field_sample_id(sample, thing):
@@ -183,32 +169,22 @@ def test_patch_sample(sample):
     """
     Test updating a sample.
     """
-    new_sampler_name = "Test Sampler B"
-    new_sample_method = "continuous"
-    new_sample_date = "2025-01-02T00:00:00Z"
-    response = client.patch(
-        f"/sample/{sample.id}",
-        json={
-            "sampler_name": new_sampler_name,
-            "sample_method": new_sample_method,
-            "sample_date": new_sample_date,
-        },
-    )
+    payload = {
+        "sampler_name": "test sample b",
+        "sample_method": "continuous",
+        "sample_date": "2025-01-02T00:00:00Z",
+    }
+    response = client.patch(f"/sample/{sample.id}", json=payload)
     assert response.status_code == 200
     data = response.json()
 
     assert data["id"] == sample.id
-    assert data["sampler_name"] == new_sampler_name
-    assert data["sample_date"] == new_sample_date
-    assert data["sample_method"] == new_sample_method
+    assert data["sampler_name"] == payload["sampler_name"]
+    assert data["sample_date"] == payload["sample_date"]
+    assert data["sample_method"] == payload["sample_method"]
 
     # rollback after updating the sample
-    with session_ctx() as session:
-        updated_sample = session.get(Sample, sample.id)
-        updated_sample.sampler_name = sample.sampler_name
-        updated_sample.sample_method = sample.sample_method
-        updated_sample.sample_date = sample.sample_date
-        session.commit()
+    cleanup_patch_test(Sample, payload, sample)
 
 
 def test_patch_sample_404_not_found(sample):
diff --git a/tests/test_sensor.py b/tests/test_sensor.py
index e01cbb035..7b514059b 100644
--- a/tests/test_sensor.py
+++ b/tests/test_sensor.py
@@ -13,35 +13,29 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 # ===============================================================================
+from core.dependencies import admin_function, editor_function, viewer_function
 from db import Sensor
-from db.engine import session_ctx
+from main import app
 from schemas.sensor import ValidateSensor
-from tests import client, cleanup_post_test, cleanup_patch_test
+from tests import client, cleanup_post_test, cleanup_patch_test, override_authentication
 
 import pytest
 from pydantic import ValidationError
 
-# ====== module functions and fixtures =========================================
 
+@pytest.fixture(scope="module", autouse=True)
+def override_dependencies_fixture():
+    app.dependency_overrides[admin_function] = override_authentication(
+        default={"name": "foobar", "sub": "1234567890"}
+    )
+    app.dependency_overrides[editor_function] = override_authentication(
+        default={"name": "foobar", "sub": "1234567890"}
+    )
+    app.dependency_overrides[viewer_function] = override_authentication()
 
-@pytest.fixture(scope="function")
-def second_sensor():
-    with session_ctx() as session:
-        sensor = Sensor(
-            name="Test Sensor 2",
-            model="Model X",
-            serial_no="123456",
-            datetime_installed="2023-01-01T00:00:00Z",
-            datetime_removed="2023-01-02T00:00:00Z",
-            recording_interval=60,
-            notes="Test equipment",
-        )
-        session.add(sensor)
-        session.commit()
-        yield sensor
-        session.delete(sensor)
-        session.commit()
-        session.close()
+    yield
+
+    app.dependency_overrides = {}
 
 
 # ====== VALIDATION tests ======================================================