diff --git a/tests/app/billing/test_rest.py b/tests/app/billing/test_rest.py
index e1dfc33d3..5c82cabab 100644
--- a/tests/app/billing/test_rest.py
+++ b/tests/app/billing/test_rest.py
@@ -155,7 +155,7 @@ def test_get_yearly_usage_by_monthly_from_ft_billing(admin_request, notify_db_se
     )
 
     sms_template = create_template(service=service, template_type=TemplateType.SMS)
-    email_template = create_template(service=service, template_type="email")
+    email_template = create_template(service=service, template_type=TemplateType.EMAIL)
 
     for dt in (date(2016, 1, 28), date(2016, 8, 10), date(2016, 12, 26)):
         create_ft_billing(local_date=dt, template=sms_template, rate=0.0162)
@@ -171,7 +171,11 @@ def test_get_yearly_usage_by_monthly_from_ft_billing(admin_request, notify_db_se
 
     assert len(json_response) == 3  # 3 billed months for SMS
 
-    email_rows = [row for row in json_response if row["notification_type"] == "email"]
+    email_rows = [
+        row
+        for row in json_response
+        if row["notification_type"] == NotificationType.EMAIL
+    ]
     assert len(email_rows) == 0
 
     sms_row = next(
diff --git a/tests/app/celery/test_nightly_tasks.py b/tests/app/celery/test_nightly_tasks.py
index 0e98d0f48..0c496fb2c 100644
--- a/tests/app/celery/test_nightly_tasks.py
+++ b/tests/app/celery/test_nightly_tasks.py
@@ -104,10 +104,10 @@ def test_will_remove_csv_files_for_jobs_older_than_retention_period(
         days_of_retention=30,
     )
     sms_template_service_1 = create_template(service=service_1)
-    email_template_service_1 = create_template(service=service_1, template_type="email")
+    email_template_service_1 = create_template(service=service_1, template_type=TemplateType.EMAIL,)
 
     sms_template_service_2 = create_template(service=service_2)
-    email_template_service_2 = create_template(service=service_2, template_type="email")
+    email_template_service_2 = create_template(service=service_2, template_type=TemplateType.EMAIL,)
 
     four_days_ago = datetime.utcnow() - timedelta(days=4)
     eight_days_ago = datetime.utcnow() - timedelta(days=8)
@@ -153,7 +153,7 @@ def test_delete_email_notifications_older_than_retentions_calls_child_task(
         "app.celery.nightly_tasks._delete_notifications_older_than_retention_by_type"
     )
     delete_email_notifications_older_than_retention()
-    mocked_notifications.assert_called_once_with("email")
+    mocked_notifications.assert_called_once_with(NotificationType.EMAIL)
 
 
 @freeze_time("2021-12-13T10:00")
@@ -352,10 +352,10 @@ def test_delete_notifications_task_calls_task_for_services_that_have_sent_notifi
     create_template(service_will_delete_1)
     create_template(service_will_delete_2)
     nothing_to_delete_sms_template = create_template(
-        service_nothing_to_delete, template_type=TemplateType.SMS
+        service_nothing_to_delete, template_type=TemplateType.SMS,
     )
     nothing_to_delete_email_template = create_template(
-        service_nothing_to_delete, template_type="email"
+        service_nothing_to_delete, template_type=TemplateType.EMAIL,
     )
 
     # will be deleted as service has no custom retention, but past our default 7 days
diff --git a/tests/app/celery/test_service_callback_tasks.py b/tests/app/celery/test_service_callback_tasks.py
index af1e8abd4..a39241528 100644
--- a/tests/app/celery/test_service_callback_tasks.py
+++ b/tests/app/celery/test_service_callback_tasks.py
@@ -64,14 +64,14 @@ def test_send_delivery_status_to_service_post_https_request_to_service_with_encr
     assert request_mock.request_history[0].headers["Content-type"] == "application/json"
     assert request_mock.request_history[0].headers[
         "Authorization"
-    ] == "Bearer {}".format(callback_api.bearer_token)
+    ] == f"Bearer {callback_api.bearer_token}"
 
 
 def test_send_complaint_to_service_posts_https_request_to_service_with_encrypted_data(
     notify_db_session,
 ):
     with freeze_time("2001-01-01T12:00:00"):
-        callback_api, template = _set_up_test_data("email", "complaint")
+        callback_api, template = _set_up_test_data(NotificationType.EMAIL, CallbackType.COMPLAINT,)
 
         notification = create_notification(template=template)
         complaint = create_complaint(
@@ -102,7 +102,7 @@ def test_send_complaint_to_service_posts_https_request_to_service_with_encrypted
         )
         assert request_mock.request_history[0].headers[
             "Authorization"
-        ] == "Bearer {}".format(callback_api.bearer_token)
+        ] == f"Bearer {callback_api.bearer_token}"
 
 
 @pytest.mark.parametrize(
@@ -113,7 +113,7 @@ def test_send_complaint_to_service_posts_https_request_to_service_with_encrypted
 def test__send_data_to_service_callback_api_retries_if_request_returns_error_code_with_encrypted_data(
     notify_db_session, mocker, notification_type, status_code
 ):
-    callback_api, template = _set_up_test_data(notification_type, "delivery_status")
+    callback_api, template = _set_up_test_data(notification_type, CallbackType.DELIVERY_STATUS,)
     datestr = datetime(2017, 6, 20)
     notification = create_notification(
         template=template,
@@ -143,7 +143,7 @@ def test__send_data_to_service_callback_api_retries_if_request_returns_error_cod
 def test__send_data_to_service_callback_api_does_not_retry_if_request_returns_404_with_encrypted_data(
     notify_db_session, mocker, notification_type
 ):
-    callback_api, template = _set_up_test_data(notification_type, "delivery_status")
+    callback_api, template = _set_up_test_data(notification_type, CallbackType.DELIVERY_STATUS,)
     datestr = datetime(2017, 6, 20)
     notification = create_notification(
         template=template,
@@ -178,7 +178,7 @@ def test_send_delivery_status_to_service_succeeds_if_sent_at_is_none(
         created_at=datestr,
         updated_at=datestr,
         sent_at=None,
-        status="technical-failure",
+        status=NotificationStatus.TECHNICAL_FAILURE,
     )
     encrypted_data = _set_up_data_for_status_update(callback_api, notification)
     mocked = mocker.patch(
diff --git a/tests/app/celery/test_tasks.py b/tests/app/celery/test_tasks.py
index 7d61e28ad..a3ea1baf9 100644
--- a/tests/app/celery/test_tasks.py
+++ b/tests/app/celery/test_tasks.py
@@ -116,7 +116,7 @@ def test_should_process_sms_job(sample_job, mocker):
         queue="database-tasks",
     )
     job = jobs_dao.dao_get_job_by_id(sample_job.id)
-    assert job.job_status == "finished"
+    assert job.job_status == JobStatus.FINISHED
 
 
 def test_should_process_sms_job_with_sender_id(sample_job, mocker, fake_uuid):
@@ -138,7 +138,7 @@ def test_should_process_sms_job_with_sender_id(sample_job, mocker, fake_uuid):
 
 
 def test_should_not_process_job_if_already_pending(sample_template, mocker):
-    job = create_job(template=sample_template, job_status="scheduled")
+    job = create_job(template=sample_template, job_status=JobStatus.SCHEDULED)
 
     mocker.patch("app.celery.tasks.s3.get_job_and_metadata_from_s3")
     mocker.patch("app.celery.tasks.process_row")
@@ -153,7 +153,7 @@ def test_should_process_job_if_send_limits_are_not_exceeded(
     notify_api, notify_db_session, mocker
 ):
     service = create_service(message_limit=10)
-    template = create_template(service=service, template_type="email")
+    template = create_template(service=service, template_type=TemplateType.EMAIL)
     job = create_job(template=template, notification_count=10)
 
     mocker.patch(
@@ -169,7 +169,7 @@ def test_should_process_job_if_send_limits_are_not_exceeded(
         service_id=str(job.service.id), job_id=str(job.id)
     )
     job = jobs_dao.dao_get_job_by_id(job.id)
-    assert job.job_status == "finished"
+    assert job.job_status == JobStatus.FINISHED
     tasks.save_email.apply_async.assert_called_with(
         (
             str(job.service_id),
@@ -238,7 +238,7 @@ def test_should_process_email_job(email_job_with_placeholders, mocker):
         queue="database-tasks",
     )
     job = jobs_dao.dao_get_job_by_id(email_job_with_placeholders.id)
-    assert job.job_status == "finished"
+    assert job.job_status == JobStatus.FINISHED
 
 
 def test_should_process_email_job_with_sender_id(
@@ -293,7 +293,7 @@ def test_should_process_all_sms_job(sample_job_with_placeholdered_template, mock
     }
     assert tasks.save_sms.apply_async.call_count == 10
     job = jobs_dao.dao_get_job_by_id(sample_job_with_placeholdered_template.id)
-    assert job.job_status == "finished"
+    assert job.job_status == JobStatus.FINISHED
 
 
 # -------------- process_row tests -------------- #
@@ -311,7 +311,7 @@ def test_process_row_sends_letter_task(
 ):
     mocker.patch("app.celery.tasks.create_uuid", return_value="noti_uuid")
     task_mock = mocker.patch(
-        "app.celery.tasks.{}.apply_async".format(expected_function)
+        f"app.celery.tasks.{expected_function}.apply_async"
     )
     encrypt_mock = mocker.patch("app.celery.tasks.encryption.encrypt")
     template = Mock(id="template_id", template_type=template_type)
@@ -1041,7 +1041,7 @@ def test_send_inbound_sms_to_service_post_https_request_to_service(
     assert request_mock.request_history[0].headers["Content-type"] == "application/json"
     assert request_mock.request_history[0].headers[
         "Authorization"
-    ] == "Bearer {}".format(inbound_api.bearer_token)
+    ] == f"Bearer {inbound_api.bearer_token}"
 
 
 def test_send_inbound_sms_to_service_does_not_send_request_when_inbound_sms_does_not_exist(
diff --git a/tests/app/conftest.py b/tests/app/conftest.py
index 44e93b98b..86386d731 100644
--- a/tests/app/conftest.py
+++ b/tests/app/conftest.py
@@ -19,6 +19,7 @@ from app.dao.services_dao import dao_add_user_to_service, dao_create_service
 from app.dao.templates_dao import dao_create_template
 from app.dao.users_dao import create_secret_code, create_user_code
 from app.enums import (
+    JobStatus,
     KeyType,
     NotificationStatus,
     RecipientType,
@@ -160,7 +161,7 @@ def service_factory(sample_user):
                 user=user,
                 check_if_service_exists=True,
             )
-            if template_type == "email":
+            if template_type == TemplateType.EMAIL:
                 create_template(
                     service,
                     template_name="Template Name",
@@ -381,7 +382,7 @@ def sample_job(notify_db_session):
         "notification_count": 1,
         "created_at": datetime.utcnow(),
         "created_by": service.created_by,
-        "job_status": "pending",
+        "job_status": JobStatus.PENDING,
         "scheduled_for": None,
         "processing_started": None,
         "archived": False,
@@ -405,7 +406,7 @@ def sample_job_with_placeholdered_template(
 def sample_scheduled_job(sample_template_with_placeholders):
     return create_job(
         sample_template_with_placeholders,
-        job_status="scheduled",
+        job_status=JobStatus.SCHEDULED,
         scheduled_for=(datetime.utcnow() + timedelta(minutes=60)).isoformat(),
     )
 
@@ -420,7 +421,7 @@ def sample_notification_with_job(notify_db_session):
         job=job,
         job_row_number=None,
         to_field=None,
-        status="created",
+        status=NotificationStatus.CREATED,
         reference=None,
         created_at=None,
         sent_at=None,
@@ -525,7 +526,7 @@ def sample_notification_history(notify_db_session, sample_template):
         service=sample_template.service,
         template_id=sample_template.id,
         template_version=sample_template.version,
-        status="created",
+        status=NotificationStatus.CREATED,
         created_at=created_at,
         notification_type=notification_type,
         key_type=KeyType.NORMAL,
@@ -572,7 +573,7 @@ def sample_expired_user(notify_db_session):
         "permissions": "send_messages,manage_service,manage_api_keys",
         "folder_permissions": ["folder_1_id", "folder_2_id"],
         "created_at": datetime.utcnow() - timedelta(days=3),
-        "status": "expired",
+        "status": NotificationStatus.EXPIRED,
     }
     expired_user = InvitedUser(**data)
     save_invited_user(expired_user)
@@ -639,7 +640,7 @@ def email_2fa_code_template(notify_service):
             "((url))"
         ),
         subject="Sign in to GOV.UK Notify",
-        template_type="email",
+        template_type=TemplateType.EMAIL,
     )
 
 
@@ -650,7 +651,7 @@ def email_verification_template(notify_service):
         user=notify_service.users[0],
         template_config_name="NEW_USER_EMAIL_VERIFICATION_TEMPLATE_ID",
         content="((user_name)) use ((url)) to complete registration",
-        template_type="email",
+        template_type=TemplateType.EMAIL,
     )
 
 
@@ -665,7 +666,7 @@ def invitation_email_template(notify_service):
         template_config_name="INVITATION_EMAIL_TEMPLATE_ID",
         content=content,
         subject="Invitation to ((service_name))",
-        template_type="email",
+        template_type=TemplateType.EMAIL,
     )
 
 
@@ -677,7 +678,7 @@ def org_invite_email_template(notify_service):
         template_config_name="ORGANIZATION_INVITATION_EMAIL_TEMPLATE_ID",
         content="((user_name)) ((organization_name)) ((url))",
         subject="Invitation to ((organization_name))",
-        template_type="email",
+        template_type=TemplateType.EMAIL,
     )
 
 
@@ -689,7 +690,7 @@ def password_reset_email_template(notify_service):
         template_config_name="PASSWORD_RESET_TEMPLATE_ID",
         content="((user_name)) you can reset password by clicking ((url))",
         subject="Reset your password",
-        template_type="email",
+        template_type=TemplateType.EMAIL,
     )
 
 
@@ -701,7 +702,7 @@ def verify_reply_to_address_email_template(notify_service):
         template_config_name="REPLY_TO_EMAIL_ADDRESS_VERIFICATION_TEMPLATE_ID",
         content="Hi,This address has been provided as the reply-to email address so we are verifying if it's working",
         subject="Your GOV.UK Notify reply-to email address",
-        template_type="email",
+        template_type=TemplateType.EMAIL,
     )
 
 
@@ -713,7 +714,7 @@ def team_member_email_edit_template(notify_service):
         template_config_name="TEAM_MEMBER_EDIT_EMAIL_TEMPLATE_ID",
         content="Hi ((name)) ((servicemanagername)) changed your email to ((email address))",
         subject="Your GOV.UK Notify email address has changed",
-        template_type="email",
+        template_type=TemplateType.EMAIL,
     )
 
 
@@ -737,7 +738,7 @@ def already_registered_template(notify_service):
         user=notify_service.users[0],
         template_config_name="ALREADY_REGISTERED_EMAIL_TEMPLATE_ID",
         content=content,
-        template_type="email",
+        template_type=TemplateType.EMAIL,
     )
 
 
@@ -753,7 +754,7 @@ def change_email_confirmation_template(notify_service):
         user=notify_service.users[0],
         template_config_name="CHANGE_EMAIL_CONFIRMATION_TEMPLATE_ID",
         content=content,
-        template_type="email",
+        template_type=TemplateType.EMAIL,
     )
     return template
 
@@ -771,7 +772,7 @@ def mou_signed_templates(notify_service):
             notify_service,
             notify_service.users[0],
             config_name,
-            "email",
+            TemplateType.EMAIL,
             content="\n".join(
                 next(
                     x
@@ -862,7 +863,7 @@ def sample_inbound_numbers(sample_service):
     inbound_numbers.append(create_inbound_number(number="1", provider="sns"))
     inbound_numbers.append(
         create_inbound_number(
-            number="2", provider="sns", active=False, service_id=service.id
+            number="2", provider="sns", active=False, service_id=service.id,
         )
     )
     return inbound_numbers
diff --git a/tests/app/dao/test_complaint_dao.py b/tests/app/dao/test_complaint_dao.py
index 4a293ffc5..2f6f3d866 100644
--- a/tests/app/dao/test_complaint_dao.py
+++ b/tests/app/dao/test_complaint_dao.py
@@ -7,6 +7,7 @@ from app.dao.complaint_dao import (
     fetch_paginated_complaints,
     save_complaint,
 )
+from app.enums import TemplateType
 from app.models import Complaint
 from tests.app.db import (
     create_complaint,
@@ -72,8 +73,8 @@ def test_fetch_complaint_by_service_returns_empty_list(sample_service):
 def test_fetch_complaint_by_service_return_many(notify_db_session):
     service_1 = create_service(service_name="first")
     service_2 = create_service(service_name="second")
-    template_1 = create_template(service=service_1, template_type="email")
-    template_2 = create_template(service=service_2, template_type="email")
+    template_1 = create_template(service=service_1, template_type=TemplateType.EMAIL)
+    template_2 = create_template(service=service_2, template_type=TemplateType.EMAIL)
     notification_1 = create_notification(template=template_1)
     notification_2 = create_notification(template=template_2)
     notification_3 = create_notification(template=template_2)
@@ -138,13 +139,13 @@ def test_fetch_count_of_complaints(sample_email_notification):
     )
 
     count_of_complaints = fetch_count_of_complaints(
-        start_date=datetime(2018, 6, 7), end_date=datetime(2018, 6, 7)
+        start_date=datetime(2018, 6, 7), end_date=datetime(2018, 6, 7),
     )
     assert count_of_complaints == 5
 
 
 def test_fetch_count_of_complaints_returns_zero(notify_db_session):
     count_of_complaints = fetch_count_of_complaints(
-        start_date=datetime(2018, 6, 7), end_date=datetime(2018, 6, 7)
+        start_date=datetime(2018, 6, 7), end_date=datetime(2018, 6, 7),
     )
     assert count_of_complaints == 0
diff --git a/tests/app/dao/test_service_data_retention_dao.py b/tests/app/dao/test_service_data_retention_dao.py
index f800bd464..bb5765fe7 100644
--- a/tests/app/dao/test_service_data_retention_dao.py
+++ b/tests/app/dao/test_service_data_retention_dao.py
@@ -57,7 +57,7 @@ def test_fetch_service_data_retention_returns_empty_list_when_no_rows_for_servic
 
 
 def test_fetch_service_data_retention_by_id(sample_service):
-    email_data_retention = insert_service_data_retention(sample_service.id, "email", 3)
+    email_data_retention = insert_service_data_retention(sample_service.id, NotificationType.EMAIL, 3,)
     insert_service_data_retention(sample_service.id, NotificationType.SMS, 13)
     result = fetch_service_data_retention_by_id(
         sample_service.id, email_data_retention.id
diff --git a/tests/app/dao/test_services_dao.py b/tests/app/dao/test_services_dao.py
index 990315260..3aa50738e 100644
--- a/tests/app/dao/test_services_dao.py
+++ b/tests/app/dao/test_services_dao.py
@@ -511,7 +511,7 @@ def test_dao_fetch_live_services_data(sample_user):
     create_service(service_name="restricted", restricted=True)
     create_service(service_name="not_active", active=False)
     create_service(service_name="not_live", count_as_live=False)
-    email_template = create_template(service=service, template_type="email")
+    email_template = create_template(service=service, template_type=TemplateType.EMAIL)
     dao_add_service_to_organization(service=service, organization_id=org.id)
     # two sms billing records for 1st service within current financial year:
     create_ft_billing(local_date="2019-04-20", template=sms_template)
@@ -1217,8 +1217,8 @@ def test_dao_fetch_todays_stats_for_all_services_only_includes_today(notify_db_s
         stats = dao_fetch_todays_stats_for_all_services()
 
     stats = {row.status: row.count for row in stats}
-    assert "delivered" not in stats
-    assert stats["failed"] == 1
+    assert NotificationStatus.DELIVERED not in stats
+    assert stats[NotificationStatus.FAILED] == 1
 
 
 def test_dao_fetch_todays_stats_for_all_services_groups_correctly(notify_db_session):
diff --git a/tests/app/db.py b/tests/app/db.py
index 9de87ba48..ec8098cf5 100644
--- a/tests/app/db.py
+++ b/tests/app/db.py
@@ -141,7 +141,7 @@ def create_service(
             created_by=user
             if user
             else create_user(
-                email="{}@digital.cabinet-office.gov.uk".format(uuid.uuid4())
+                email=f"{uuid.uuid4()}@digital.cabinet-office.gov.uk"
             ),
             prefix_sms=prefix_sms,
             organization_type=organization_type,
@@ -212,7 +212,7 @@ def create_template(
     contact_block_id=None,
 ):
     data = {
-        "name": template_name or "{} Template Name".format(template_type),
+        "name": template_name or f"{template_type} Template Name",
         "template_type": template_type,
         "content": content,
         "service": service,
@@ -353,7 +353,7 @@ def create_notification_history(
     if created_at is None:
         created_at = datetime.utcnow()
 
-    if status != "created":
+    if status != NotificationStatus.CREATED:
         sent_at = sent_at or datetime.utcnow()
         updated_at = updated_at or datetime.utcnow()
 
@@ -498,7 +498,7 @@ def create_service_callback_api(
 
 
 def create_email_branding(
-    id=None, colour="blue", logo="test_x2.png", name="test_org_1", text="DisplayName"
+    id=None, colour="blue", logo="test_x2.png", name="test_org_1", text="DisplayName",
 ):
     data = {
         "colour": colour,
@@ -529,7 +529,7 @@ def create_rate(start_date, value, notification_type):
 def create_api_key(service, key_type=KeyType.NORMAL, key_name=None):
     id_ = uuid.uuid4()
 
-    name = key_name if key_name else "{} api key {}".format(key_type, id_)
+    name = key_name if key_name else f"{key_type} api key {id_}"
 
     api_key = ApiKey(
         service=service,
@@ -644,7 +644,7 @@ def create_organization(
 
 
 def create_invited_org_user(
-    organization, invited_by, email_address="invite@example.com"
+    organization, invited_by, email_address="invite@example.com",
 ):
     invited_org_user = InvitedOrganizationUser(
         email_address=email_address,
@@ -752,7 +752,7 @@ def create_complaint(service=None, notification=None, created_at=None):
     if not service:
         service = create_service()
     if not notification:
-        template = create_template(service=service, template_type="email")
+        template = create_template(service=service, template_type=TemplateType.EMAIL)
         notification = create_notification(template=template)
 
     complaint = Complaint(
@@ -907,7 +907,7 @@ def set_up_usage_data(start_date):
         financial_year_start=year,
     )
     org_1 = create_organization(
-        name="Org for {}".format(service_1_sms_and_letter.name),
+        name=f"Org for {service_1_sms_and_letter.name}",
         purchase_order_number="org1 purchase order number",
         billing_contact_names="org1 billing contact names",
         billing_contact_email_addresses="org1@billing.contact email@addresses.gov.uk",
@@ -918,13 +918,13 @@ def set_up_usage_data(start_date):
     )
 
     create_ft_billing(
-        local_date=one_week_earlier, template=sms_template_1, billable_unit=2, rate=0.11
+        local_date=one_week_earlier, template=sms_template_1, billable_unit=2, rate=0.11,
     )
     create_ft_billing(
-        local_date=start_date, template=sms_template_1, billable_unit=2, rate=0.11
+        local_date=start_date, template=sms_template_1, billable_unit=2, rate=0.11,
     )
     create_ft_billing(
-        local_date=two_days_later, template=sms_template_1, billable_unit=1, rate=0.11
+        local_date=two_days_later, template=sms_template_1, billable_unit=1, rate=0.11,
     )
 
     # service with emails only:
@@ -933,7 +933,7 @@ def set_up_usage_data(start_date):
         service=service_with_emails, template_type=TemplateType.EMAIL
     )
     org_2 = create_organization(
-        name="Org for {}".format(service_with_emails.name),
+        name=f"Org for {service_with_emails.name}",
     )
     dao_add_service_to_organization(
         service=service_with_emails, organization_id=org_2.id
diff --git a/tests/app/notifications/test_validators.py b/tests/app/notifications/test_validators.py
index 25d4695bf..10ab1e031 100644
--- a/tests/app/notifications/test_validators.py
+++ b/tests/app/notifications/test_validators.py
@@ -119,8 +119,8 @@ def test_check_template_is_for_notification_type_fails_when_template_type_does_n
             notification_type=notification_type, template_type=template_type
         )
     assert e.value.status_code == 400
-    error_message = "{0} template is not suitable for {1} notification".format(
-        template_type, notification_type
+    error_message = (
+        f"{template_type} template is not suitable for {notification_type} notification"
     )
     assert e.value.message == error_message
     assert e.value.fields == [{"template": error_message}]
@@ -474,7 +474,7 @@ def test_validate_template_calls_all_validators_exception_message_too_long(
         check_char_count=False,
     )
 
-    mock_check_type.assert_called_once_with("email", "email")
+    mock_check_type.assert_called_once_with(NotificationType.EMAIL, TemplateType.EMAIL)
     mock_check_if_active.assert_called_once_with(template)
     mock_create_conent.assert_called_once_with(template, {})
     mock_check_not_empty.assert_called_once_with("content")
@@ -499,7 +499,7 @@ def test_check_service_over_api_rate_limit_when_exceed_rate_limit_request_fails_
             check_service_over_api_rate_limit(serialised_service, serialised_api_key)
 
         assert app.redis_store.exceeded_rate_limit.called_with(
-            "{}-{}".format(str(sample_service.id), api_key.key_type),
+            f"{sample_service.id}-{api_key.key_type}",
             sample_service.rate_limit,
             60,
         )
@@ -527,7 +527,7 @@ def test_check_service_over_api_rate_limit_when_rate_limit_has_not_exceeded_limi
 
         check_service_over_api_rate_limit(serialised_service, serialised_api_key)
         assert app.redis_store.exceeded_rate_limit.called_with(
-            "{}-{}".format(str(sample_service.id), api_key.key_type), 3000, 60
+            f"{sample_service.id}-{api_key.key_type}", 3000, 60,
         )
 
 
@@ -583,7 +583,7 @@ def test_validate_and_format_recipient_fails_when_international_number_and_servi
     assert e.value.fields == []
 
 
-@pytest.mark.parametrize("key_type", ["test", "normal"])
+@pytest.mark.parametrize("key_type", [KeyType.TEST, KeyType.NORMAL])
 def test_validate_and_format_recipient_succeeds_with_international_numbers_if_service_does_allow_int_sms(
     key_type, sample_service_full_permissions
 ):
@@ -597,7 +597,7 @@ def test_validate_and_format_recipient_succeeds_with_international_numbers_if_se
 def test_validate_and_format_recipient_fails_when_no_recipient():
     with pytest.raises(BadRequestError) as e:
         validate_and_format_recipient(
-            None, "key_type", "service", "NotificationType.SMS"
+            None, KeyType.NORMAL, "service", NotificationType.SMS,
         )
     assert e.value.status_code == 400
     assert e.value.message == "Recipient can't be empty"
@@ -632,8 +632,9 @@ def test_check_service_email_reply_to_id_where_service_id_is_not_found(
     assert e.value.status_code == 400
     assert (
         e.value.message
-        == "email_reply_to_id {} does not exist in database for service id {}".format(
-            reply_to_address.id, fake_uuid
+        == (
+            f"email_reply_to_id {reply_to_address.id} does not exist in database for i"
+            f"service id {fake_uuid}"
         )
     )
 
@@ -648,8 +649,9 @@ def test_check_service_email_reply_to_id_where_reply_to_id_is_not_found(
     assert e.value.status_code == 400
     assert (
         e.value.message
-        == "email_reply_to_id {} does not exist in database for service id {}".format(
-            fake_uuid, sample_service.id
+        == (
+            f"email_reply_to_id {fake_uuid} does not exist in database for service "
+            f"id {sample_service.id}"
         )
     )
 
@@ -683,8 +685,9 @@ def test_check_service_sms_sender_id_where_service_id_is_not_found(
     assert e.value.status_code == 400
     assert (
         e.value.message
-        == "sms_sender_id {} does not exist in database for service id {}".format(
-            sms_sender.id, fake_uuid
+        == (
+            f"sms_sender_id {sms_sender.id} does not exist in database for service "
+            f"id {fake_uuid}"
         )
     )
 
@@ -697,8 +700,9 @@ def test_check_service_sms_sender_id_where_sms_sender_is_not_found(
     assert e.value.status_code == 400
     assert (
         e.value.message
-        == "sms_sender_id {} does not exist in database for service id {}".format(
-            fake_uuid, sample_service.id
+        == (
+            f"sms_sender_id {fake_uuid} does not exist in database for service "
+            f"id {sample_service.id}"
         )
     )
 
diff --git a/tests/app/service/test_rest.py b/tests/app/service/test_rest.py
index a825c5acb..9c5dd174c 100644
--- a/tests/app/service/test_rest.py
+++ b/tests/app/service/test_rest.py
@@ -151,7 +151,7 @@ def test_find_services_by_name_handles_no_results(
     mock_get_services_by_partial_name = mocker.patch(
         "app.service.rest.get_services_by_partial_name", return_value=[]
     )
-    response = admin_request.get("service.find_services_by_name", service_name="ABC")[
+    response = admin_request.get("service.find_services_by_name", service_name="ABC",)[
         "data"
     ]
     mock_get_services_by_partial_name.assert_called_once_with("ABC")
@@ -330,7 +330,7 @@ def test_get_service_by_id_and_user(client, sample_service, sample_user):
     create_reply_to_email(service=sample_service, email_address="new@service.com")
     auth_header = create_admin_authorization_header()
     resp = client.get(
-        "/service/{}?user_id={}".format(sample_service.id, sample_user.id),
+        f"/service/{sample_service.id}?user_id={sample_user.id}",
         headers=[auth_header],
     )
     assert resp.status_code == 200
@@ -345,7 +345,7 @@ def test_get_service_by_id_should_404_if_no_service_for_user(notify_api, sample_
             service_id = str(uuid.uuid4())
             auth_header = create_admin_authorization_header()
             resp = client.get(
-                "/service/{}?user_id={}".format(service_id, sample_user.id),
+                f"/service/{service_id}?user_id={sample_user.id}",
                 headers=[auth_header],
             )
             assert resp.status_code == 404
@@ -448,7 +448,7 @@ def test_create_service_with_domain_sets_organization(
     create_domain("fake.gov", another_org.id)
     create_domain("cabinetoffice.gov.uk", another_org.id)
 
-    sample_user.email_address = "test@{}".format(domain)
+    sample_user.email_address = f"test@{domain}"
 
     data = {
         "name": "created service",
@@ -657,7 +657,7 @@ def test_should_not_create_service_with_duplicate_name(
             json_resp = resp.json
             assert json_resp["result"] == "error"
             assert (
-                "Duplicate service name '{}'".format(sample_service.name)
+                f"Duplicate service name '{sample_service.name}'"
                 in json_resp["message"]["name"]
             )
 
@@ -685,7 +685,7 @@ def test_create_service_should_throw_duplicate_key_constraint_for_existing_email
             json_resp = resp.json
             assert json_resp["result"] == "error"
             assert (
-                "Duplicate service name '{}'".format(service_name)
+                f"Duplicate service name '{service_name}'"
                 in json_resp["message"]["name"]
             )
 
@@ -712,7 +712,7 @@ def test_update_service(client, notify_db_session, sample_service):
     auth_header = create_admin_authorization_header()
 
     resp = client.post(
-        "/service/{}".format(sample_service.id),
+        f"/service/{sample_service.id}",
         data=json.dumps(data),
         headers=[("Content-Type", "application/json"), auth_header],
     )
@@ -735,7 +735,7 @@ def test_cant_update_service_org_type_to_random_value(client, sample_service):
     auth_header = create_admin_authorization_header()
 
     resp = client.post(
-        "/service/{}".format(sample_service.id),
+        f"/service/{sample_service.id}",
         data=json.dumps(data),
         headers=[("Content-Type", "application/json"), auth_header],
     )
@@ -784,7 +784,7 @@ def test_update_service_change_email_branding(
 
 def test_update_service_flags(client, sample_service):
     auth_header = create_admin_authorization_header()
-    resp = client.get("/service/{}".format(sample_service.id), headers=[auth_header])
+    resp = client.get(f"/service/{sample_service.id}", headers=[auth_header])
     json_resp = resp.json
     assert resp.status_code == 200
     assert json_resp["data"]["name"] == sample_service.name
@@ -793,7 +793,7 @@ def test_update_service_flags(client, sample_service):
     auth_header = create_admin_authorization_header()
 
     resp = client.post(
-        "/service/{}".format(sample_service.id),
+        f"/service/{sample_service.id}",
         data=json.dumps(data),
         headers=[("Content-Type", "application/json"), auth_header],
     )
@@ -879,7 +879,7 @@ def test_update_service_flags_with_service_without_default_service_permissions(
     }
 
     resp = client.post(
-        "/service/{}".format(service_with_no_permissions.id),
+        f"/service/{service_with_no_permissions.id}",
         data=json.dumps(data),
         headers=[("Content-Type", "application/json"), auth_header],
     )
@@ -911,7 +911,7 @@ def test_update_service_flags_will_remove_service_permissions(
     data = {"permissions": [ServicePermissionType.SMS, ServicePermissionType.EMAIL]}
 
     resp = client.post(
-        "/service/{}".format(service.id),
+        f"/service/{service.id}",
         data=json.dumps(data),
         headers=[("Content-Type", "application/json"), auth_header],
     )
@@ -935,7 +935,7 @@ def test_update_permissions_will_override_permission_flags(
     data = {"permissions": [ServicePermissionType.INTERNATIONAL_SMS]}
 
     resp = client.post(
-        "/service/{}".format(service_with_no_permissions.id),
+        f"/service/{service_with_no_permissions.id}",
         data=json.dumps(data),
         headers=[("Content-Type", "application/json"), auth_header],
     )
@@ -955,7 +955,7 @@ def test_update_service_permissions_will_add_service_permissions(
     data = {"permissions": [ServicePermissionType.EMAIL, ServicePermissionType.SMS]}
 
     resp = client.post(
-        "/service/{}".format(sample_service.id),
+        f"/service/{sample_service.id}",
         data=json.dumps(data),
         headers=[("Content-Type", "application/json"), auth_header],
     )
@@ -986,7 +986,7 @@ def test_add_service_permission_will_add_permission(
     data = {"permissions": [permission_to_add]}
 
     resp = client.post(
-        "/service/{}".format(service_with_no_permissions.id),
+        f"/service/{service_with_no_permissions.id}",
         data=json.dumps(data),
         headers=[("Content-Type", "application/json"), auth_header],
     )
@@ -1014,7 +1014,7 @@ def test_update_permissions_with_an_invalid_permission_will_raise_error(
     }
 
     resp = client.post(
-        "/service/{}".format(sample_service.id),
+        f"/service/{sample_service.id}",
         data=json.dumps(data),
         headers=[("Content-Type", "application/json"), auth_header],
     )
@@ -1023,7 +1023,7 @@ def test_update_permissions_with_an_invalid_permission_will_raise_error(
     assert resp.status_code == 400
     assert result["result"] == "error"
     assert (
-        "Invalid Service Permission: '{}'".format(invalid_permission)
+        f"Invalid Service Permission: '{invalid_permission}'"
         in result["message"]["permissions"]
     )
 
@@ -1042,7 +1042,7 @@ def test_update_permissions_with_duplicate_permissions_will_raise_error(
     }
 
     resp = client.post(
-        "/service/{}".format(sample_service.id),
+        f"/service/{sample_service.id}",
         data=json.dumps(data),
         headers=[("Content-Type", "application/json"), auth_header],
     )
@@ -1070,7 +1070,7 @@ def test_should_not_update_service_with_duplicate_name(
             auth_header = create_admin_authorization_header()
 
             resp = client.post(
-                "/service/{}".format(sample_service.id),
+                f"/service/{sample_service.id}",
                 data=json.dumps(data),
                 headers=[("Content-Type", "application/json"), auth_header],
             )
@@ -1078,7 +1078,7 @@ def test_should_not_update_service_with_duplicate_name(
             json_resp = resp.json
             assert json_resp["result"] == "error"
             assert (
-                "Duplicate service name '{}'".format(service_name)
+                f"Duplicate service name '{service_name}'"
                 in json_resp["message"]["name"]
             )
 
@@ -1102,7 +1102,7 @@ def test_should_not_update_service_with_duplicate_email_from(
             auth_header = create_admin_authorization_header()
 
             resp = client.post(
-                "/service/{}".format(sample_service.id),
+                f"/service/{sample_service.id}",
                 data=json.dumps(data),
                 headers=[("Content-Type", "application/json"), auth_header],
             )
@@ -1110,9 +1110,9 @@ def test_should_not_update_service_with_duplicate_email_from(
             json_resp = resp.json
             assert json_resp["result"] == "error"
             assert (
-                "Duplicate service name '{}'".format(service_name)
+                f"Duplicate service name '{service_name}'"
                 in json_resp["message"]["name"]
-                or "Duplicate service name '{}'".format(email_from)
+                or f"Duplicate service name '{email_from}'"
                 in json_resp["message"]["name"]
             )
 
@@ -1127,7 +1127,7 @@ def test_update_service_should_404_if_id_is_invalid(notify_api):
             auth_header = create_admin_authorization_header()
 
             resp = client.post(
-                "/service/{}".format(missing_service_id),
+                f"/service/{missing_service_id}",
                 data=json.dumps(data),
                 headers=[("Content-Type", "application/json"), auth_header],
             )
@@ -1141,7 +1141,7 @@ def test_get_users_by_service(notify_api, sample_service):
             auth_header = create_admin_authorization_header()
 
             resp = client.get(
-                "/service/{}/users".format(sample_service.id),
+                f"/service/{sample_service.id}/users",
                 headers=[("Content-Type", "application/json"), auth_header],
             )
 
@@ -1162,7 +1162,7 @@ def test_get_users_for_service_returns_empty_list_if_no_users_associated_with_se
             auth_header = create_admin_authorization_header()
 
             response = client.get(
-                "/service/{}/users".format(sample_service.id),
+                f"/service/{sample_service.id}/users",
                 headers=[("Content-Type", "application/json"), auth_header],
             )
             result = json.loads(response.get_data(as_text=True))
@@ -1179,7 +1179,7 @@ def test_get_users_for_service_returns_404_when_service_does_not_exist(
             auth_header = create_admin_authorization_header()
 
             response = client.get(
-                "/service/{}/users".format(service_id),
+                f"/service/{service_id}/users",
                 headers=[("Content-Type", "application/json"), auth_header],
             )
             assert response.status_code == 404
@@ -1215,15 +1215,13 @@ def test_default_permissions_are_added_for_user_service(
             auth_header_fetch = create_admin_authorization_header()
 
             resp = client.get(
-                "/service/{}?user_id={}".format(
-                    json_resp["data"]["id"], sample_user.id
-                ),
+                f"/service/{json_resp['data']['id']}?user_id={sample_user.id}",
                 headers=[auth_header_fetch],
             )
             assert resp.status_code == 200
             header = create_admin_authorization_header()
             response = client.get(
-                url_for("user.get_user", user_id=sample_user.id), headers=[header]
+                url_for("user.get_user", user_id=sample_user.id), headers=[header],
             )
             assert response.status_code == 200
             json_resp = json.loads(response.get_data(as_text=True))
@@ -1246,7 +1244,7 @@ def test_add_existing_user_to_another_service_with_all_permissions(
             auth_header = create_admin_authorization_header()
 
             resp = client.get(
-                "/service/{}/users".format(sample_service.id),
+                f"/service/{sample_service.id}/users",
                 headers=[("Content-Type", "application/json"), auth_header],
             )
 
@@ -1284,7 +1282,7 @@ def test_add_existing_user_to_another_service_with_all_permissions(
             auth_header = create_admin_authorization_header()
 
             resp = client.post(
-                "/service/{}/users/{}".format(sample_service.id, user_to_add.id),
+                f"/service/{sample_service.id}/users/{user_to_add.id}",
                 headers=[("Content-Type", "application/json"), auth_header],
                 data=json.dumps(data),
             )
@@ -1295,7 +1293,7 @@ def test_add_existing_user_to_another_service_with_all_permissions(
             auth_header = create_admin_authorization_header()
 
             resp = client.get(
-                "/service/{}".format(sample_service.id),
+                f"/service/{sample_service.id}",
                 headers=[("Content-Type", "application/json"), auth_header],
             )
             assert resp.status_code == 200
@@ -1312,13 +1310,13 @@ def test_add_existing_user_to_another_service_with_all_permissions(
             json_resp = resp.json
             permissions = json_resp["data"]["permissions"][str(sample_service.id)]
             expected_permissions = [
-                "send_texts",
-                "send_emails",
-                "manage_users",
-                "manage_settings",
-                "manage_templates",
-                "manage_api_keys",
-                "view_activity",
+                PermissionType.SEND_TEXTS,
+                PermissionType.SEND_EMAILS,
+                PermissionType.MANAGE_USERS,
+                PermissionType.MANAGE_SETTINGS,
+                PermissionType.MANAGE_TEMPLATES,
+                PermissionType.MANAGE_API_KEYS,
+                PermissionType.VIEW_ACTIVITY,
             ]
             assert sorted(expected_permissions) == sorted(permissions)
 
@@ -1348,7 +1346,7 @@ def test_add_existing_user_to_another_service_with_send_permissions(
             auth_header = create_admin_authorization_header()
 
             resp = client.post(
-                "/service/{}/users/{}".format(sample_service.id, user_to_add.id),
+                f"/service/{sample_service.id}/users/{user_to_add.id}",
                 headers=[("Content-Type", "application/json"), auth_header],
                 data=json.dumps(data),
             )
@@ -1395,7 +1393,7 @@ def test_add_existing_user_to_another_service_with_manage_permissions(
             auth_header = create_admin_authorization_header()
 
             resp = client.post(
-                "/service/{}/users/{}".format(sample_service.id, user_to_add.id),
+                f"/service/{sample_service.id}/users/{user_to_add.id}",
                 headers=[("Content-Type", "application/json"), auth_header],
                 data=json.dumps(data),
             )
@@ -1446,7 +1444,7 @@ def test_add_existing_user_to_another_service_with_folder_permissions(
             auth_header = create_admin_authorization_header()
 
             resp = client.post(
-                "/service/{}/users/{}".format(sample_service.id, user_to_add.id),
+                f"/service/{sample_service.id}/users/{user_to_add.id}",
                 headers=[("Content-Type", "application/json"), auth_header],
                 data=json.dumps(data),
             )
@@ -1481,7 +1479,7 @@ def test_add_existing_user_to_another_service_with_manage_api_keys(
             auth_header = create_admin_authorization_header()
 
             resp = client.post(
-                "/service/{}/users/{}".format(sample_service.id, user_to_add.id),
+                f"/service/{sample_service.id}/users/{user_to_add.id}",
                 headers=[("Content-Type", "application/json"), auth_header],
                 data=json.dumps(data),
             )
@@ -1519,12 +1517,12 @@ def test_add_existing_user_to_non_existing_service_returns404(
             incorrect_id = uuid.uuid4()
 
             data = {
-                "permissions": ["send_messages", "manage_service", "manage_api_keys"]
+                "permissions": [PermissionType.SEND_EMAILS, PermissionType.SEND_TEXTS, PermissionType.MANAGE_USERS, PermissionType.MANAGE_SETTINGS, PermissionType.MANAGE_TEMPLATES, PermissionType.MANAGE_API_KEYS,]
             }
             auth_header = create_admin_authorization_header()
 
             resp = client.post(
-                "/service/{}/users/{}".format(incorrect_id, user_to_add.id),
+                f"/service/{incorrect_id}/users/{user_to_add.id}",
                 headers=[("Content-Type", "application/json"), auth_header],
                 data=json.dumps(data),
             )
@@ -1545,19 +1543,20 @@ def test_add_existing_user_of_service_to_service_returns400(
             existing_user_id = sample_service.users[0].id
 
             data = {
-                "permissions": ["send_messages", "manage_service", "manage_api_keys"]
+                "permissions": [PermissionType.SEND_EMAILS, PermissionType.SEND_TEXTS, PermissionType.MANAGE_USERS, PermissionType.MANAGE_SETTINGS, PermissionType.MANAGE_TEMPLATES, PermissionType.MANAGE_API_KEYS,]
             }
             auth_header = create_admin_authorization_header()
 
             resp = client.post(
-                "/service/{}/users/{}".format(sample_service.id, existing_user_id),
+                f"/service/{sample_service.id}/users/{existing_user_id}",
                 headers=[("Content-Type", "application/json"), auth_header],
                 data=json.dumps(data),
             )
 
             result = resp.json
-            expected_message = "User id: {} already part of service id: {}".format(
-                existing_user_id, sample_service.id
+            expected_message = (
+                f"User id: {existing_user_id} already part of service "
+                f"id: {sample_service.id}"
             )
 
             assert resp.status_code == 400
@@ -1573,12 +1572,12 @@ def test_add_unknown_user_to_service_returns404(
             incorrect_id = 9876
 
             data = {
-                "permissions": ["send_messages", "manage_service", "manage_api_keys"]
+                "permissions": [PermissionType.SEND_EMAILS, PermissionType.SEND_TEXTS, PermissionType.MANAGE_USERS, PermissionType.MANAGE_SETTINGS, PermissionType.MANAGE_TEMPLATES, PermissionType.MANAGE_API_KEYS,]
             }
             auth_header = create_admin_authorization_header()
 
             resp = client.post(
-                "/service/{}/users/{}".format(sample_service.id, incorrect_id),
+                f"/service/{sample_service.id}/users/{incorrect_id}",
                 headers=[("Content-Type", "application/json"), auth_header],
                 data=json.dumps(data),
             )
@@ -1660,7 +1659,7 @@ def test_get_service_and_api_key_history(notify_api, sample_service, sample_api_
         with notify_api.test_client() as client:
             auth_header = create_admin_authorization_header()
             response = client.get(
-                path="/service/{}/history".format(sample_service.id),
+                path=f"/service/{sample_service.id}/history",
                 headers=[auth_header],
             )
             assert response.status_code == 200
@@ -1691,7 +1690,7 @@ def test_get_all_notifications_for_service_in_order(client, notify_db_session):
     auth_header = create_admin_authorization_header()
 
     response = client.get(
-        path="/service/{}/notifications".format(service_1.id), headers=[auth_header]
+        path=f"/service/{service_1.id}/notifications", headers=[auth_header]
     )
 
     resp = json.loads(response.get_data(as_text=True))
@@ -1790,9 +1789,7 @@ def test_get_all_notifications_for_service_formatted_for_csv(client, sample_temp
     auth_header = create_admin_authorization_header()
 
     response = client.get(
-        path="/service/{}/notifications?format_for_csv=True".format(
-            sample_template.service_id
-        ),
+        path=f"/service/{sample_template.service_id}/notifications?format_for_csv=True",
         headers=[auth_header],
     )
 
@@ -1809,7 +1806,7 @@ def test_get_all_notifications_for_service_formatted_for_csv(client, sample_temp
 def test_get_notification_for_service_without_uuid(client, notify_db_session):
     service_1 = create_service(service_name="1", email_from="1")
     response = client.get(
-        path="/service/{}/notifications/{}".format(service_1.id, "foo"),
+        path=f"/service/{service_1.id}/notifications/{'foo'}",
         headers=[create_admin_authorization_header()],
     )
     assert response.status_code == 404
@@ -1832,7 +1829,7 @@ def test_get_notification_for_service(client, notify_db_session):
 
     for notification in service_1_notifications:
         response = client.get(
-            path="/service/{}/notifications/{}".format(service_1.id, notification.id),
+            path=f"/service/{service_1.id}/notifications/{notification.id}",
             headers=[create_admin_authorization_header()],
         )
         resp = json.loads(response.get_data(as_text=True))
@@ -1840,7 +1837,7 @@ def test_get_notification_for_service(client, notify_db_session):
         assert response.status_code == 200
 
         service_2_response = client.get(
-            path="/service/{}/notifications/{}".format(service_2.id, notification.id),
+            path=f"/service/{service_2.id}/notifications/{notification.id}",
             headers=[create_admin_authorization_header()],
         )
         assert service_2_response.status_code == 404
@@ -1909,8 +1906,9 @@ def test_get_all_notifications_for_service_including_ones_made_by_jobs(
     auth_header = create_admin_authorization_header()
 
     response = client.get(
-        path="/service/{}/notifications?include_from_test_key={}".format(
-            sample_service.id, include_from_test_key
+        path=(
+            f"/service/{sample_service.id}/notifications?include_from_test_key="
+            f"{include_from_test_key}"
         ),
         headers=[auth_header],
     )
@@ -2084,9 +2082,7 @@ def test_get_detailed_service(
     with freeze_time("2000-01-02T12:00:00"):
         create_notification(template=sample_template, status="created")
         resp = client.get(
-            "/service/{}?detailed=True&today_only={}".format(
-                sample_service.id, today_only
-            ),
+            f"/service/{sample_service.id}?detailed=True&today_only={today_only}",
             headers=[create_admin_authorization_header()],
         )
 
@@ -2197,10 +2193,10 @@ def test_get_detailed_services_groups_by_service(notify_db_session):
     service_1_template = create_template(service_1)
     service_2_template = create_template(service_2)
 
-    create_notification(service_1_template, status="created")
-    create_notification(service_2_template, status="created")
-    create_notification(service_1_template, status="delivered")
-    create_notification(service_1_template, status="created")
+    create_notification(service_1_template, status=NotificationStatus.CREATED)
+    create_notification(service_2_template, status=NotificationStatus.CREATED)
+    create_notification(service_1_template, status=NotificationStatus.DELIVERED)
+    create_notification(service_1_template, status=NotificationStatus.CREATED)
 
     data = get_detailed_services(
         start_date=datetime.utcnow().date(), end_date=datetime.utcnow().date()
@@ -2210,13 +2206,13 @@ def test_get_detailed_services_groups_by_service(notify_db_session):
     assert len(data) == 2
     assert data[0]["id"] == str(service_1.id)
     assert data[0]["statistics"] == {
-        NotificationType.EMAIL.value: {"delivered": 0, "failed": 0, "requested": 0},
-        NotificationType.SMS.value: {"delivered": 1, "failed": 0, "requested": 3},
+        NotificationType.EMAIL.value: {NotificationStatus.DELIVERED: 0, NotificationStatus.FAILED: 0, "requested": 0,},
+        NotificationType.SMS.value: {NotificationStatus.DELIVERED: 1, NotificationStatus.FAILED: 0, "requested": 3,},
     }
     assert data[1]["id"] == str(service_2.id)
     assert data[1]["statistics"] == {
-        NotificationType.EMAIL.value: {"delivered": 0, "failed": 0, "requested": 0},
-        NotificationType.SMS.value: {"delivered": 0, "failed": 0, "requested": 1},
+        NotificationType.EMAIL.value: {NotificationStatus.DELIVERED: 0, NotificationStatus.FAILED: 0, "requested": 0,},
+        NotificationType.SMS.value: {NotificationStatus.DELIVERED: 0, NotificationStatus.FAILED: 0, "requested": 1,},
     }
 
 
@@ -2239,13 +2235,13 @@ def test_get_detailed_services_includes_services_with_no_notifications(
     assert len(data) == 2
     assert data[0]["id"] == str(service_1.id)
     assert data[0]["statistics"] == {
-        NotificationType.EMAIL.value: {"delivered": 0, "failed": 0, "requested": 0},
-        NotificationType.SMS.value: {"delivered": 0, "failed": 0, "requested": 1},
+        NotificationType.EMAIL.value: {NotificationStatus.DELIVERED: 0, NotificationStatus.FAILED: 0, "requested": 0,},
+        NotificationType.SMS.value: {NotificationStatus.DELIVERED: 0, NotificationStatus.FAILED: 0, "requested": 1,},
     }
     assert data[1]["id"] == str(service_2.id)
     assert data[1]["statistics"] == {
-        NotificationType.EMAIL.value: {"delivered": 0, "failed": 0, "requested": 0},
-        NotificationType.SMS.value: {"delivered": 0, "failed": 0, "requested": 0},
+        NotificationType.EMAIL.value: {NotificationStatus.DELIVERED: 0, NotificationStatus.FAILED: 0, "requested": 0,},
+        NotificationType.SMS.value: {NotificationStatus.DELIVERED: 0, NotificationStatus.FAILED: 0, "requested": 0,},
     }
 
 
@@ -2265,8 +2261,8 @@ def test_get_detailed_services_only_includes_todays_notifications(sample_templat
 
     assert len(data) == 1
     assert data[0]["statistics"] == {
-        NotificationType.EMAIL.value: {"delivered": 0, "failed": 0, "requested": 0},
-        NotificationType.SMS.value: {"delivered": 0, "failed": 0, "requested": 3},
+        NotificationType.EMAIL.value: {NotificationStatus.DELIVERED: 0, NotificationStatus.FAILED: 0, "requested": 0,},
+        NotificationType.SMS.value: {NotificationStatus.DELIVERED: 0, NotificationStatus.FAILED: 0, "requested": 3,},
     }
 
 
@@ -2311,13 +2307,13 @@ def test_get_detailed_services_for_date_range(
 
     assert len(data) == 1
     assert data[0]["statistics"][NotificationType.EMAIL.value] == {
-        "delivered": 0,
-        "failed": 0,
+        NotificationStatus.DELIVERED: 0,
+        NotificationStatus.FAILED: 0,
         "requested": 0,
     }
     assert data[0]["statistics"][NotificationType.SMS.value] == {
-        "delivered": 2,
-        "failed": 0,
+        NotificationStatus.DELIVERED: 2,
+        NotificationStatus.FAILED: 0,
         "requested": 2,
     }
 
@@ -2338,9 +2334,8 @@ def test_search_for_notification_by_to_field(
     )
 
     response = client.get(
-        "/service/{}/notifications?to={}&template_type={}".format(
-            notification1.service_id, "jack@gmail.com", "email"
-        ),
+        f"/service/{notification1.service_id}/notifications?to={'jack@gmail.com'}"
+        f"&template_type={TemplateType.EMAIL}",
         headers=[create_admin_authorization_header()],
     )
     notifications = json.loads(response.get_data(as_text=True))["notifications"]
@@ -2377,16 +2372,16 @@ def test_search_for_notification_by_to_field_return_multiple_matches(
     client, sample_template, sample_email_template
 ):
     notification1 = create_notification(
-        sample_template, to_field="+447700900855", normalised_to="447700900855"
+        sample_template, to_field="+447700900855", normalised_to="447700900855",
     )
     notification2 = create_notification(
-        sample_template, to_field=" +44 77009 00855 ", normalised_to="447700900855"
+        sample_template, to_field=" +44 77009 00855 ", normalised_to="447700900855",
     )
     notification3 = create_notification(
-        sample_template, to_field="+44770 0900 855", normalised_to="447700900855"
+        sample_template, to_field="+44770 0900 855", normalised_to="447700900855",
     )
     notification4 = create_notification(
-        sample_email_template, to_field="jack@gmail.com", normalised_to="jack@gmail.com"
+        sample_email_template, to_field="jack@gmail.com", normalised_to="jack@gmail.com",
     )
 
     response = client.get(
@@ -2414,7 +2409,7 @@ def test_search_for_notification_by_to_field_returns_next_link_if_more_than_50(
 ):
     for _ in range(51):
         create_notification(
-            sample_template, to_field="+447700900855", normalised_to="447700900855"
+            sample_template, to_field="+447700900855", normalised_to="447700900855",
         )
 
     response = client.get(
@@ -2438,7 +2433,7 @@ def test_search_for_notification_by_to_field_returns_no_next_link_if_50_or_less(
 ):
     for _ in range(50):
         create_notification(
-            sample_template, to_field="+447700900855", normalised_to="447700900855"
+            sample_template, to_field="+447700900855", normalised_to="447700900855",
         )
 
     response = client.get(
@@ -2492,7 +2487,7 @@ def test_update_service_does_not_call_send_notification_for_live_service(
 
     auth_header = create_admin_authorization_header()
     resp = client.post(
-        "service/{}".format(sample_service.id),
+        f"service/{sample_service.id}",
         data=json.dumps(data),
         headers=[auth_header],
         content_type="application/json",
@@ -3035,7 +3030,7 @@ def test_get_email_reply_to_address(client, notify_db_session):
     reply_to = create_reply_to_email(service, "test_a@mail.com")
 
     response = client.get(
-        "/service/{}/email-reply-to/{}".format(service.id, reply_to.id),
+        f"/service/{service.id}/email-reply-to/{reply_to.id}",
         headers=[
             ("Content-Type", "application/json"),
             create_admin_authorization_header(),
@@ -3053,7 +3048,7 @@ def test_add_service_sms_sender_can_add_multiple_senders(client, notify_db_sessi
         "is_default": False,
     }
     response = client.post(
-        "/service/{}/sms-sender".format(service.id),
+        f"/service/{service.id}/sms-sender",
         data=json.dumps(data),
         headers=[
             ("Content-Type", "application/json"),
diff --git a/tests/app/test_model.py b/tests/app/test_model.py
index 67a83e661..b094bb824 100644
--- a/tests/app/test_model.py
+++ b/tests/app/test_model.py
@@ -42,7 +42,7 @@ from tests.app.db import (
 @pytest.mark.parametrize("mobile_number", ["+447700900855", "+12348675309"])
 def test_should_build_service_guest_list_from_mobile_number(mobile_number):
     service_guest_list = ServiceGuestList.from_string(
-        "service_id", RecipientType.MOBILE, mobile_number
+        "service_id", RecipientType.MOBILE, mobile_number,
     )
 
     assert service_guest_list.recipient == mobile_number
@@ -51,7 +51,7 @@ def test_should_build_service_guest_list_from_mobile_number(mobile_number):
 @pytest.mark.parametrize("email_address", ["test@example.com"])
 def test_should_build_service_guest_list_from_email_address(email_address):
     service_guest_list = ServiceGuestList.from_string(
-        "service_id", RecipientType.EMAIL, email_address
+        "service_id", RecipientType.EMAIL, email_address,
     )
 
     assert service_guest_list.recipient == email_address
@@ -220,7 +220,7 @@ def test_notification_subject_is_none_for_sms(sample_service):
     assert notification.subject is None
 
 
-@pytest.mark.parametrize("template_type", ["email"])
+@pytest.mark.parametrize("template_type", [TemplateType.EMAIL])
 def test_notification_subject_fills_in_placeholders(sample_service, template_type):
     template = create_template(
         service=sample_service, template_type=template_type, subject="((name))"