diff --git a/src/protean/adapters/email/sendgrid.py b/src/protean/adapters/email/sendgrid.py
index 10943b7b..de2fbea7 100644
--- a/src/protean/adapters/email/sendgrid.py
+++ b/src/protean/adapters/email/sendgrid.py
@@ -40,9 +40,9 @@ def send_email(self, message):
             logger.debug("Email pushed to SendGrid successfully.")
         except HTTPError as e:
             logger.error(f"{e}: {e.to_dict}")
-            raise SendError(f"Exception: HTTPError - Failed to send email - str(e)")
+            raise SendError(f"Exception: HTTPError - Failed to send email - {str(e)}")
         except Exception as e:
             logger.error(f"Exception: Error while sending email: {e}")
-            raise SendError(f"Exception: Failed to send email - str(e)")
+            raise SendError(f"Exception: Failed to send email - {str(e)}")
 
         return True
diff --git a/src/protean/container.py b/src/protean/container.py
index f0f7d536..a262e33d 100644
--- a/src/protean/container.py
+++ b/src/protean/container.py
@@ -187,7 +187,7 @@ def __new__(cls, *args, **kwargs):
             raise TypeError("BaseContainer cannot be instantiated")
         return super().__new__(cls)
 
-    def __init__(self, *template, **kwargs):
+    def __init__(self, *template, **kwargs):  # noqa: C901
         """
         Initialise the container.
 
@@ -340,5 +340,5 @@ def __init__(self, *args, **kwargs) -> None:
 
         self._events = []
 
-    def raise_(self, event: "BaseEvent") -> None:
+    def raise_(self, event) -> None:
         self._events.append(event)
diff --git a/src/protean/core/event_sourced_repository.py b/src/protean/core/event_sourced_repository.py
index 48f3dbb5..56b48abb 100644
--- a/src/protean/core/event_sourced_repository.py
+++ b/src/protean/core/event_sourced_repository.py
@@ -23,7 +23,7 @@ def __new__(cls, *args, **kwargs):
             raise TypeError("BaseEventSourcedRepository cannot be instantiated")
         return super().__new__(cls)
 
-    def __init__(self, domain: "Domain") -> None:
+    def __init__(self, domain) -> None:
         self._domain = domain
 
     def add(self, aggregate: BaseEventSourcedAggregate) -> None:
diff --git a/src/protean/core/repository.py b/src/protean/core/repository.py
index 392234ab..e4973485 100644
--- a/src/protean/core/repository.py
+++ b/src/protean/core/repository.py
@@ -42,13 +42,13 @@ def __new__(cls, *args, **kwargs):
             raise TypeError("BaseRepository cannot be instantiated")
         return super().__new__(cls)
 
-    def __init__(self, domain: "Domain", provider: "BaseProvider") -> None:
+    def __init__(self, domain, provider) -> None:
         self._domain = domain
         self._provider = provider
 
     @property
     @lru_cache()
-    def _model(self) -> "BaseModel":
+    def _model(self):
         """Retrieve Model class connected to Entity"""
         # If a model was associated with the aggregate record, give it a higher priority
         #   and do not bake a new model class from aggregate/entity attributes
diff --git a/src/protean/core/unit_of_work.py b/src/protean/core/unit_of_work.py
index 3af4443b..f38cd15f 100644
--- a/src/protean/core/unit_of_work.py
+++ b/src/protean/core/unit_of_work.py
@@ -47,7 +47,7 @@ def start(self):
         self._in_progress = True
         _uow_context_stack.push(self)
 
-    def commit(self):
+    def commit(self):  # noqa: C901
         # Raise error if there the Unit Of Work is not active
         logger.debug(f"Committing {self}...")
         if not self._in_progress:
diff --git a/src/protean/server/engine.py b/src/protean/server/engine.py
index 267ecd51..70601e34 100644
--- a/src/protean/server/engine.py
+++ b/src/protean/server/engine.py
@@ -25,7 +25,7 @@
 
 
 class Engine:
-    def __init__(self, domain: "Domain", test_mode: str = False) -> None:
+    def __init__(self, domain, test_mode: str = False) -> None:
         self.domain = domain
         self.test_mode = test_mode
 
diff --git a/src/protean/server/subscription.py b/src/protean/server/subscription.py
index bf4dd621..bc7f28bb 100644
--- a/src/protean/server/subscription.py
+++ b/src/protean/server/subscription.py
@@ -21,7 +21,7 @@ class Subscription:
 
     def __init__(
         self,
-        engine: "Engine",
+        engine,
         subscriber_id: str,
         stream_name: str,
         handler: Union[BaseEventHandler, BaseCommandHandler],
diff --git a/src/protean/utils/mixins.py b/src/protean/utils/mixins.py
index 1e4ac163..0969ae50 100644
--- a/src/protean/utils/mixins.py
+++ b/src/protean/utils/mixins.py
@@ -7,6 +7,7 @@
 from typing import Callable, Dict, Union
 from uuid import uuid4
 
+from protean import fields
 from protean.container import BaseContainer, OptionsMixin
 from protean.core.command import BaseCommand
 from protean.core.event import BaseEvent
@@ -14,7 +15,6 @@
 from protean.core.unit_of_work import UnitOfWork
 from protean.core.value_object import BaseValueObject
 from protean.exceptions import ConfigurationError, IncorrectUsageError
-from protean.fields import Auto, DateTime, Dict, Integer, String, ValueObject
 from protean.globals import current_domain, g
 from protean.reflection import has_id_field, id_field
 from protean.utils import fully_qualified_name
@@ -26,22 +26,24 @@ class MessageType(Enum):
 
 
 class MessageMetadata(BaseValueObject):
-    kind = String(max_length=7, choices=MessageType)  # FIXME Make this field mandatory?
-    owner = String(max_length=50)
-    schema_version = Integer()
+    kind = fields.String(
+        max_length=7, choices=MessageType
+    )  # FIXME Make this field mandatory?
+    owner = fields.String(max_length=50)
+    schema_version = fields.Integer()
 
-    origin_stream_name = String()
+    origin_stream_name = fields.String()
 
 
 class CoreMessage(BaseContainer):
-    global_position = Auto(increment=True, identifier=True)
-    position = Integer()
-    time = DateTime()
-    id = Auto()
-    stream_name = String(max_length=255)
-    type = String()
-    data = Dict()
-    metadata = ValueObject(MessageMetadata)
+    global_position = fields.Auto(increment=True, identifier=True)
+    position = fields.Integer()
+    time = fields.DateTime()
+    id = fields.Auto()
+    stream_name = fields.String(max_length=255)
+    type = fields.String()
+    data = fields.Dict()
+    metadata = fields.ValueObject(MessageMetadata)
 
 
 class Message(CoreMessage, OptionsMixin):  # FIXME Remove OptionsMixin
@@ -52,7 +54,7 @@ class Message(CoreMessage, OptionsMixin):  # FIXME Remove OptionsMixin
     - Serialization and De-serialization
     """
 
-    expected_version = Integer()
+    expected_version = fields.Integer()
 
     @classmethod
     def derived_metadata(cls, new_message_type: str) -> Dict:
diff --git a/tests/adapters/event_store/message_db_event_store/tests.py b/tests/adapters/event_store/message_db_event_store/tests.py
index a2acb8b3..6b538e4b 100644
--- a/tests/adapters/event_store/message_db_event_store/tests.py
+++ b/tests/adapters/event_store/message_db_event_store/tests.py
@@ -23,7 +23,7 @@ def test_error_on_message_db_initialization(self):
 
         with pytest.raises(ConfigurationError) as exc:
             domain.event_store.store._write(
-                "testStream-123", "Event1", {"foo": f"bar"}, {"kind": "EVENT"}
+                "testStream-123", "Event1", {"foo": "bar"}, {"kind": "EVENT"}
             )
 
         assert 'FATAL:  database "dummy" does not exist' in str(exc.value)
diff --git a/tests/command/test_automatic_stream_association.py b/tests/command/test_automatic_stream_association.py
index 6e93e56c..1452ac1f 100644
--- a/tests/command/test_automatic_stream_association.py
+++ b/tests/command/test_automatic_stream_association.py
@@ -107,7 +107,7 @@ def test_automatic_association_of_events_with_aggregate_and_stream():
     assert Activate.meta_.aggregate_cls is None
     assert Activate.meta_.stream_name == "user"
 
-    assert Subscribe.meta_.aggregate_cls == None
+    assert Subscribe.meta_.aggregate_cls is None
     assert Subscribe.meta_.stream_name == "subscriptions"
 
     assert Send.meta_.aggregate_cls is None
diff --git a/tests/command/test_command_meta.py b/tests/command/test_command_meta.py
index 1b67144a..7d71cfd0 100644
--- a/tests/command/test_command_meta.py
+++ b/tests/command/test_command_meta.py
@@ -34,7 +34,7 @@ def test_command_definition_without_aggregate_or_stream(test_domain):
         )
     assert exc.value.messages == {
         "_entity": [
-            f"Command `Register` needs to be associated with an aggregate or a stream"
+            "Command `Register` needs to be associated with an aggregate or a stream"
         ]
     }
 
@@ -48,7 +48,7 @@ class Meta:
 
     try:
         test_domain.register(AbstractCommand)
-    except:
+    except Exception:
         pytest.fail(
             "Abstract commands should be definable without being associated with an aggregate or a stream"
         )
diff --git a/tests/event/test_automatic_stream_association.py b/tests/event/test_automatic_stream_association.py
index a2f18599..9f47ef1c 100644
--- a/tests/event/test_automatic_stream_association.py
+++ b/tests/event/test_automatic_stream_association.py
@@ -111,7 +111,7 @@ def test_automatic_association_of_events_with_aggregate_and_stream():
     assert Activated.meta_.aggregate_cls is None
     assert Activated.meta_.stream_name == "user"
 
-    assert Subscribed.meta_.aggregate_cls == None
+    assert Subscribed.meta_.aggregate_cls is None
     assert Subscribed.meta_.stream_name == "subscriptions"
 
     assert Sent.meta_.aggregate_cls is None
diff --git a/tests/event/test_event_meta.py b/tests/event/test_event_meta.py
index ff570a03..75bd9e2a 100644
--- a/tests/event/test_event_meta.py
+++ b/tests/event/test_event_meta.py
@@ -28,7 +28,7 @@ def test_event_definition_without_aggregate_or_stream(test_domain):
 
     assert exc.value.messages == {
         "_entity": [
-            f"Event `UserLoggedIn` needs to be associated with an aggregate or a stream"
+            "Event `UserLoggedIn` needs to be associated with an aggregate or a stream"
         ]
     }
 
diff --git a/tests/event_sourced_aggregates/test_applying_events.py b/tests/event_sourced_aggregates/test_applying_events.py
index 8b7d0e43..71439edc 100644
--- a/tests/event_sourced_aggregates/test_applying_events.py
+++ b/tests/event_sourced_aggregates/test_applying_events.py
@@ -105,5 +105,5 @@ def sent(self, _: Sent) -> None:
                 pass
 
     assert exc.value.messages == {
-        "_entity": [f"Apply method is missing Event class argument"]
+        "_entity": ["Apply method is missing Event class argument"]
     }
diff --git a/tests/event_store/test_appending_commands.py b/tests/event_store/test_appending_commands.py
index 172068e0..5ce9bec8 100644
--- a/tests/event_store/test_appending_commands.py
+++ b/tests/event_store/test_appending_commands.py
@@ -34,7 +34,7 @@ def test_command_submission_without_aggregate(test_domain):
         )
     assert exc.value.messages == {
         "_entity": [
-            f"Command `Register` needs to be associated with an aggregate or a stream"
+            "Command `Register` needs to be associated with an aggregate or a stream"
         ]
     }
 
diff --git a/tests/field/test_auto.py b/tests/field/test_auto.py
index 84ce0011..0bcbf701 100644
--- a/tests/field/test_auto.py
+++ b/tests/field/test_auto.py
@@ -43,7 +43,7 @@ class AutoTest(BaseAggregate):
     test_domain.register(AutoTest)
 
     auto1 = AutoTest()
-    assert auto1.auto_field == None  # Ensure value is unset before saving
+    assert auto1.auto_field is None  # Ensure value is unset before saving
     test_domain.repository_for(AutoTest).add(auto1)
     refreshed_auto1 = test_domain.repository_for(AutoTest)._dao.query.all().items[0]
     assert refreshed_auto1.auto_field == 1
@@ -62,7 +62,7 @@ class AutoTest(BaseAggregate):
     test_domain.register(AutoTest)
 
     auto1 = AutoTest()
-    assert auto1.auto_field == None  # Ensure value is unset before saving
+    assert auto1.auto_field is None  # Ensure value is unset before saving
     test_domain.repository_for(AutoTest).add(auto1)
     refreshed_auto1 = test_domain.repository_for(AutoTest)._dao.query.all().items[0]
     assert refreshed_auto1.auto_field == 1
diff --git a/tests/field/test_field_types.py b/tests/field/test_field_types.py
index a4edc5e5..1bc1fa92 100644
--- a/tests/field/test_field_types.py
+++ b/tests/field/test_field_types.py
@@ -320,8 +320,8 @@ def test_type_casting(self):
     def test_null_values(self):
         birthday = Date()
 
-        assert birthday._load(None) == None
-        assert birthday._load("") == None
+        assert birthday._load(None) is None
+        assert birthday._load("") is None
 
     def test_disallowing_datetime(self):
         birthday = Date()
@@ -379,8 +379,8 @@ def test_type_casting(self):
     def test_null_values(self):
         created_at = DateTime()
 
-        assert created_at._load(None) == None
-        assert created_at._load("") == None
+        assert created_at._load(None) is None
+        assert created_at._load("") is None
 
 
 class TestTextField:
diff --git a/tests/message/test_origin_stream_name_in_metadata.py b/tests/message/test_origin_stream_name_in_metadata.py
index 0d23c3aa..8f800680 100644
--- a/tests/message/test_origin_stream_name_in_metadata.py
+++ b/tests/message/test_origin_stream_name_in_metadata.py
@@ -69,7 +69,7 @@ def test_origin_stream_name_in_event_from_command_without_origin_stream_name(use
             name="John Doe",
         )
     )
-    assert event_message.metadata.origin_stream_name == None
+    assert event_message.metadata.origin_stream_name is None
 
 
 def test_origin_stream_name_in_event_from_command_with_origin_stream_name(user_id):
@@ -106,7 +106,7 @@ def test_origin_stream_name_in_aggregate_event_from_command_without_origin_strea
         ),
     )
 
-    assert event_message.metadata.origin_stream_name == None
+    assert event_message.metadata.origin_stream_name is None
 
 
 def test_origin_stream_name_in_aggregate_event_from_command_with_origin_stream_name(
diff --git a/tests/query/test_queryset.py b/tests/query/test_queryset.py
index 6127957f..60072deb 100644
--- a/tests/query/test_queryset.py
+++ b/tests/query/test_queryset.py
@@ -604,7 +604,7 @@ def test_last(self, test_domain):
         query = person_repo._dao.query.order_by("age")
         assert query.last.id == 2
 
-    def test_first_with_cache(self, test_domain):
+    def test_last_with_cache(self, test_domain):
         """Test that the first item is retrieved correctly from the resultset"""
         person_repo = test_domain.repository_for(Person)
 
diff --git a/tests/test_brokers.py b/tests/test_brokers.py
index 7673400e..2dffbee9 100644
--- a/tests/test_brokers.py
+++ b/tests/test_brokers.py
@@ -209,7 +209,7 @@ def test_that_event_is_persisted_on_publish(self, mocker, test_domain):
         messages = test_domain.event_store.store.read("person")
 
         assert len(messages) == 1
-        messages[0].stream_name == f"person-1234"
+        messages[0].stream_name == "person-1234"
 
 
 class TestBrokerSubscriberInitialization: