diff --git a/src/server/BreCal/api/user.py b/src/server/BreCal/api/user.py
index 2c3c1a0..14a03f8 100644
--- a/src/server/BreCal/api/user.py
+++ b/src/server/BreCal/api/user.py
@@ -11,6 +11,10 @@ bp = Blueprint('user', __name__)
 @bp.route('/user', methods=['put'])
 @auth_guard() # no restriction by role
 def PutUser():
+    # #TODO: user validation should be extended by the notifications. When someone wants to set
+    # notify_email = 1, the email must be either present or part of the loadedModel
+    # notify_whatsapp = 1, there must be a phone number (same for notify_signal)
+    # notify_push = 1, there must be a phone number (#TODO_determine ... or an app-id? Unclear still)
 
     try:
         content = request.get_json(force=True)
diff --git a/src/server/BreCal/database/sql_queries.py b/src/server/BreCal/database/sql_queries.py
index 51a3dea..3f84d75 100644
--- a/src/server/BreCal/database/sql_queries.py
+++ b/src/server/BreCal/database/sql_queries.py
@@ -213,7 +213,7 @@ class SQLQuery():
 
     @staticmethod
     def get_history()->str:
-        query = "SELECT id, participant_id, shipcall_id, timestamp, eta, type, operation FROM history WHERE shipcall_id = ?shipcallid?"
+        query = "SELECT id, participant_id, shipcall_id, user_id, timestamp, eta, type, operation FROM history WHERE shipcall_id = ?shipcallid?"
         return query
     
     @staticmethod
@@ -402,14 +402,14 @@ class SQLQuery():
     
     @staticmethod
     def get_notification_post()->str:
-        raise NotImplementedError()
+        raise NotImplementedError("skeleton")
         # #TODO: this query is wrong and just a proxy for a POST request
         query = "INSERT INTO shipcall_participant_map (shipcall_id, participant_id, type) VALUES (?shipcall_id?, ?participant_id?, ?type?)"
         return query
     
     @staticmethod
     def get_shipcall_put_notification_state()->str:
-        raise NotImplementedError()
+        raise NotImplementedError("skeleton")
         # #TODO: use evaluation_notifications_sent here and consider only the shipcall_id
         # #TODO: query
         query = ...
diff --git a/src/server/BreCal/impl/history.py b/src/server/BreCal/impl/history.py
index 53f159c..a2e1cb0 100644
--- a/src/server/BreCal/impl/history.py
+++ b/src/server/BreCal/impl/history.py
@@ -23,7 +23,7 @@ def GetHistory(options):
         if "shipcall_id" in options and options["shipcall_id"]:
             # query = SQLQuery.get_history()
             # data = commands.query(query, model=History.from_query_row, param={"shipcallid" : options["shipcall_id"]})
-            data = commands.query("SELECT id, participant_id, shipcall_id, timestamp, eta, type, operation FROM history WHERE shipcall_id = ?shipcallid?",
+            data = commands.query("SELECT id, participant_id, shipcall_id, user_id, timestamp, eta, type, operation FROM history WHERE shipcall_id = ?shipcallid?",
                                   model=History.from_query_row,
                                   param={"shipcallid" : options["shipcall_id"]})
 
diff --git a/src/server/BreCal/notifications/notification_functions.py b/src/server/BreCal/notifications/notification_functions.py
index 78bd6bd..c1c2e45 100644
--- a/src/server/BreCal/notifications/notification_functions.py
+++ b/src/server/BreCal/notifications/notification_functions.py
@@ -48,6 +48,8 @@ class NotifierFunctions():
 
         returns bool, whether a notification should be triggered
         """
+        # #TODO_delete: has been refactored to Notifier.check_higher_severity(old_state:model.EvaluationType, new_state:model.EvaluationType)
+
         # state_old is always considered at least 'Green' (1)
         if state_old is None:
             state_old = StatusFlags.NONE.value
@@ -65,6 +67,6 @@ class NotifierFunctions():
         return evaluation_notifications_sent
 
 
-class Notifier(NotifierFunctions):
+class LegacyNotifier(NotifierFunctions):
     def __init__(self):
         super().__init__()
diff --git a/src/server/BreCal/notifications/notifier.py b/src/server/BreCal/notifications/notifier.py
new file mode 100644
index 0000000..dc74b91
--- /dev/null
+++ b/src/server/BreCal/notifications/notifier.py
@@ -0,0 +1,313 @@
+import typing
+from BreCal.database.sql_handler import execute_sql_query_standalone
+from BreCal.database.sql_queries import SQLQuery
+from BreCal.schemas import model
+
+class Notifier():
+    """
+    This class provides quick access to different notification functions.
+    Each method is callable without initializing the Notifier object. 
+
+    Example:
+        Notifier.send_notifications(*args)
+
+    The Notifier has three main methods.
+        Notifier.send_notifications() --- can be called routinely. Identifies all candidates and notifies the users
+        Notifier.send_notification(shipcall) --- applies filters to identify, whether a notification is desired. If so, notifies the users
+        Notifer.create(user) --- 'naive' method, which simply creates a message and sends it to the user's preferred choice
+
+        # #TODO_determine: it makes sense to go one step finer. .create could produce messages and recipients, whereas .publish may then issue those and .document may update the SQL dataset
+        ## naming idea: Notifier.send_notifications, Notifier.send_notification, Notifier.send (which may contain .create, .publish, .document)
+    """
+    def __init__(self) -> None:
+        pass
+
+    @staticmethod
+    def send_notifications(is_test:bool=False) -> None:
+        """
+        This method is used in BreCal.services.schedule_routines and will issue notifications, once they are due.
+        It is purposely defined in a way, where no external dependencies or arguments are required. The only exception is the
+        'is_test' boolean, as it prevents the notifications from being *actually* sent as part of the pytests.
+
+        Steps:
+            - get all shipcalls
+            - filter: consider only those, which are not yet sent (uses shipcall.evaluation_notifications_sent)
+            - iterate over each remaining shipcall and apply .send_notification
+            - those which are unsent, shall be sent by the respective type
+        """
+        raise NotImplementedError("skeleton")
+
+        # get all shipcalls
+        all_shipcalls = NotImplementedError
+
+        shipcalls = [shipcall for shipcall in all_shipcalls if not shipcall.evaluation_notifications_sent]
+        for shipcall in shipcalls:
+            notification_list = Notifier.send_notification(shipcall, is_test=is_test)
+
+        # #TODO: get all notifications
+        # #TODO: get matching shipcall (based on shipcall_id)
+
+        # #TODO: filter: consider only those, which are not yet sent
+
+        # identify necessity
+        # #TODO: get the 'evaluation_notifications_sent' field from all shipcalls (based on shipcall_id)
+        # if not -> return
+        # USE shipcall.evaluation_notifications_sent
+
+        # #TODO: those which are unsent, shall be created&sent by the respective type -- Note: consider the is_test argument
+        # iterate over the list of Notifier.build_notification_type_list
+        #       one might use Notifier.create(..., update_database=True)
+        # use the History (GetHistory -- by shipcall_id) to identify all subscribed users
+
+        # #TODO: update the shipcall dataset ('evaluation_notifications_sent') -- Note: consider the is_test argument
+
+        # #TODO_clarify: how to handle the 'evaluation_notifications_sent', when there is no recipient?
+        return
+    
+    @staticmethod
+    def send_notification(shipcall:model.Shipcall, is_test:bool=False)->list[model.Notification]:
+        """
+        Complex-function, which is responsible of creating notification messages, issuing them to users and optionally updating
+        the database. The requirement is, that the notification is required and passes through an internal set of filters.
+
+        Steps:
+            - get all notifications of shipcall_id
+            - identify the assigned list of users
+            - apply all filters. When a filter triggers, exit. If not, create and send a notification. 
+        """
+        update_database = False if is_test else True
+        # #TODO: the concept of old state and new state must be refactored.
+        # old state: read shipcall_id from notifications and look for the latest finding (if None -> EvaluationType.undefined)
+        # new state: read shipcall_id from shipcalls and look for the *current* 'evaluation' (-> EvaluationType(value))
+
+        # get existing notifications by shipcall_id (list)
+        existing_notifications = Notifier.get_existing_notifications(shipcall_id=shipcall.id)
+        old_state = NotImplementedError
+
+        new_state = shipcall.evaluation
+
+        # get User by querying all History objects of a shipcall_id
+        users = Notifier.get_users_via_history(shipcall_id=shipcall.id)
+
+        # identify necessity
+        # state-check: Did the 'evaluation' shift to a higher level of severity?
+        severity_bool = Notifier.check_higher_severity(old_state, new_state)
+        if not severity_bool:
+            return None
+        
+        
+        # #TODO: time-based filter. There shall be 'enough' time between the evaluation time and NOW
+        evaluation_time = shipcall.evaluation_time
+        # latency_bool = #TODO_DIFFERENCE_FROM_NOW_TO_EVALUATION_TIME____THIS_METHOD_ALREADY_EXISTS(evaluation_time)
+        # careful: what is True, what is False?
+        # if latency_booL:
+        #    return None
+
+        notification_list = []
+        for user in users:
+            notification = Notifier.create(
+                shipcall.id, 
+                old_state, 
+                new_state, 
+                user,
+                update_database=update_database, 
+                is_test=is_test
+            )
+            notification_list.append(notification)
+        return notification_list
+    
+    @staticmethod
+    def publish(shipcall_id, old_state, new_state, user, update_database:bool=False)->typing.Optional[model.Notification]:
+        """
+        Complex-function, which creates, sends and documents a notification. It serves as a convenience function.
+        The method does not apply internal filters to identify, whether a notification should be created in the first place.
+
+        options:
+            update_database: bool. 
+            # #TODO: instead of update_database, one may also use is_test
+        """
+        # 1.) create
+        # ... = Notifier.create(shipcall_id, old_state, new_state, user)    # e.g., might return a dictionary of dict[model.NotificationType, str], where str is the message
+
+        # 2.) send
+        # ... = Notifier.send(...)      # should contain internal 'logistics', which user the respective handlers to send notifications
+
+        # 3.) document (mysql database)
+        # if update_database
+        # ... = Notifier.document(...)
+        raise NotImplementedError("skeleton")
+        return
+
+    @staticmethod
+    def create(shipcall_id, old_state, new_state, user, update_database:bool=False)->typing.Optional[model.Notification]:
+        """
+        Standalone function, which creates a Notification for a specific user.
+
+        Steps:
+            - identify a list of notification_types, which shall be issued (based on the user's 'notify_*' settings)
+            - create messages based on the respective NotificationType, which the user has enabled
+            - send the messages
+            - update the shipcall dataset ('evaluation_notifications_sent')
+
+        args:
+            update_database: whether to update the MySQL database by posting the notification. 
+        """
+        assert user.id is not None
+        assert shipcall_id is not None
+        assert old_state is not None
+        assert new_state is not None
+
+        # get Shipcall by shipcall_id
+        shipcall = Notifier.get_shipcall(shipcall_id=shipcall_id)
+
+        """
+        ## TODO: this might simply be removed due to incorrect concept
+        ##      could also relocate this to the generation function, which identifies the notifications to be created
+        ##      should be unnecessary due to shipcall.evaluation_notifications_sent
+
+        # a) filter existing notifictions and consider only the dataset, where type (notification_type) and level (new_state) are suitable
+        notification_exists = Notifier.check_notification_type_and_level_exists(shipcall_id=shipcall_id, notification_type=notification_type, level=new_state, existing_notifications=existing_notifications)
+        if notification_exists:
+            return None
+        """
+        
+
+        # get a list of all subscribed notification types and track the state (success or failure)
+        successes = {}
+        notification_type_list = Notifier.build_notification_type_list(user)
+        for notification_type in notification_type_list:
+            # generate message based on the notification type
+            message = Notifier.generate_notification_message_by_type(notification_type, evaluation_message=shipcall.evaluation_message, user=user)
+
+            # send the message
+            success_state = Notifier.send_notification_by_type(notification_type, message)
+            successes[notification_type] = success_state
+
+        raise NotImplementedError("skeleton")
+        notification = ...
+        return notification
+
+    @staticmethod
+    def find_latest_notification(notifications:list[model.Notification])->typing.Optional[model.Notification]:
+        """given a list of notification objects, this method returns the object, where the .created field corresponds to the *latest* notification object"""
+        latest_notification = sorted(notifications, key=lambda notification: notification.created, reverse=False)[-1] if len(notifications)>0 else None
+        return latest_notification
+    
+    @staticmethod
+    def get_users_via_history(shipcall_id:int)->list[model.User]:
+        """using the History objects, one can infer the user_id, which allows querying the Users"""
+        histories = execute_sql_query_standalone(query=SQLQuery.get_history(), param={"shipcallid" : shipcall_id}, model=model.History, command_type="query")
+        user_ids = [
+            history.user_id
+            for history in histories
+        ]
+        users = [Notifier.get_user(user_id) for user_id in user_ids]
+        return users
+    
+    @staticmethod
+    def get_user(user_id:int)->model.User:
+        """Given a user_id, this method executes an SQL query to return a User"""
+        user = execute_sql_query_standalone(query=SQLQuery.get_user_by_id(), param={"id" : user_id}, model=model.User, command_type="single")
+        return user
+    
+    @staticmethod
+    def get_shipcall(shipcall_id:int)->model.Shipcall:
+        """Given a shipcall_id, this method executes an SQL query to return a Shipcall"""
+        shipcall = execute_sql_query_standalone(query=SQLQuery.get_shipcall_by_id(), param={"id" : shipcall_id}, model=model.Shipcall.from_query_row, command_type="single")
+        return shipcall
+    
+    @staticmethod
+    def get_existing_notifications(shipcall_id:int)->list[model.Notification]:
+        existing_notifications = execute_sql_query_standalone(query=SQLQuery.get_notifications(), param={"scid" : shipcall_id}, model=model.Notification, command_type="query")
+        return existing_notifications
+    
+    @staticmethod
+    def build_notification_type_list(user:model.User)->list[model.NotificationType]:
+        """
+        based on a User, this method generates a list of notification types. These can be used as instructions to
+        generate the respective Notification datasets.
+        """
+        notification_type_list = []
+
+        if user.notify_email:
+            notification_type_list.append(model.NotificationType.email)
+
+        if user.notify_popup:
+            notification_type_list.append(model.NotificationType.push)
+
+        if user.notify_whatsapp:
+            # currently not defined as a data model. Must be included / changed, once the data model of NotificationType is updated
+            notification_type_list.append(model.NotificationType.undefined)
+
+        if user.notify_signal:
+            # currently not defined as a data model. Must be included / changed, once the data model of NotificationType is updated
+            notification_type_list.append(model.NotificationType.undefined)
+        return notification_type_list
+
+    @staticmethod
+    def check_notification_type_and_level_exists(shipcall_id:int, notification_type:model.NotificationType, level:model.EvaluationType, existing_notifications:list[model.Notification])->bool:
+        """This method checks, whether one of the Notification elements in the provided list is a perfect match to the arguments shipcall_id, notification_type and level"""
+        # #TODO_determine: should a notification be *skipped*, when there already is a dataset with
+        # identical level and type?  ---> currently enabled.
+
+        # check, if any of the existing notifications is a perfect match for notification type & level & shipcall
+        matches = [note for note in existing_notifications if (int(level)==int(note.level)) and (int(note.type)==int(notification_type)) and (shipcall_id==note.shipcall_id)]
+        
+        # bool: whether there is a perfect match
+        exists = len(matches)>0
+        raise Exception("deprecated")
+        return exists
+
+    @staticmethod
+    def check_higher_severity(old_state:model.EvaluationType, new_state:model.EvaluationType)->bool:
+        """
+        determines, whether the observed state change should trigger a notification. 
+        internally, this function maps StatusFlags to an integer and determines, if the successor state is more severe than the predecessor.
+
+        state changes trigger a notification in the following cases:
+            green -> yellow
+            green -> red
+            yellow -> red
+
+            (none -> yellow) or (none -> red)
+            due to the values in the enumeration objects, the states are mapped to provide this function.
+            green=1, yellow=2, red=3, none=1. Hence, critical changes can be observed by simply checking with "greater than". 
+
+        returns bool, whether a notification should be triggered
+        """
+        # undefined previous state: .undefined (0)
+        if old_state is None:
+            old_state = model.EvaluationType.undefined
+
+        # old_state is always considered at least .green (1) (hence, .undefined becomes .green)
+        old_state = max(int(old_state), model.EvaluationType.green)
+
+        # the IntEnum values are correctly sequenced. .red > .yellow > .green > .undefined
+        # as .undefined becomes .green, an old_state is always *at least* green. 
+        severity_grew = int(new_state) > int(old_state)
+        return severity_grew
+    
+    @staticmethod
+    def generate_notification_message_by_type(notification_type:model.NotificationType, evaluation_message:str, user:model.User):
+        assert isinstance(user, model.User)
+
+        if int(notification_type) == int(model.NotificationType.undefined):
+            raise NotImplementedError("skeleton")
+        elif int(notification_type) == int(model.NotificationType.email):
+            raise NotImplementedError("skeleton")
+        elif int(notification_type) == int(model.NotificationType.push):
+            raise NotImplementedError("skeleton")
+        #elif int(notification_type) == int(model.NotificationType.whatsapp):
+            #raise NotImplementedError("skeleton")
+        #elif int(notification_type) == int(model.NotificationType.signal):
+            #raise NotImplementedError("skeleton")
+        elif int(notification_type) == int(model.NotificationType.undefined):
+            raise NotImplementedError("skeleton")
+        else:
+            raise ValueError(notification_type)
+        return
+    
+
+
+"""# build the list of evaluation times ('now', as isoformat)"""
+#evaluation_times = [datetime.datetime.now().isoformat() for _i in range(len(evaluation_states_new))]
\ No newline at end of file
diff --git a/src/server/BreCal/schemas/model.py b/src/server/BreCal/schemas/model.py
index 92232e2..395905b 100644
--- a/src/server/BreCal/schemas/model.py
+++ b/src/server/BreCal/schemas/model.py
@@ -85,10 +85,11 @@ class ShipcallType(IntEnum):
 
 @dataclass
 class History:
-    def __init__(self, id, participant_id, shipcall_id, timestamp, eta, type, operation):
+    def __init__(self, id, participant_id, shipcall_id, user_id, timestamp, eta, type, operation):
         self.id = id
         self.participant_id = participant_id
         self.shipcall_id = shipcall_id
+        self.user_id = user_id
         self.timestamp = timestamp
         self.eta = eta
         self.type = type
@@ -98,6 +99,7 @@ class History:
     id: int
     participant_id: int
     shipcall_id: int
+    user_id: int
     timestamp: datetime
     eta: datetime
     type: ObjectType
@@ -108,6 +110,7 @@ class History:
             "id": self.id,
             "participant_id": self.participant_id,
             "shipcall_id": self.shipcall_id,
+            "user_id": self.user_id,
             "timestamp": self.timestamp.isoformat() if self.timestamp else "",
             "eta": self.eta.isoformat() if self.eta else "",
             "type": self.type.name,
@@ -115,8 +118,8 @@ class History:
         }
 
     @classmethod
-    def from_query_row(self, id, participant_id, shipcall_id, timestamp, eta, type, operation):
-        return self(id, participant_id, shipcall_id, timestamp, eta, ObjectType(type), OperationType(operation))
+    def from_query_row(self, id, participant_id, shipcall_id, user_id, timestamp, eta, type, operation):
+        return self(id, participant_id, shipcall_id, user_id, timestamp, eta, ObjectType(type), OperationType(operation))
 
 class Error(Schema):
     message = fields.String(metadata={'required':True})
@@ -135,7 +138,7 @@ class Notification:
     """
     id: int
     shipcall_id: int # 'shipcall record that caused the notification'
-    level: int # 'severity of the notification'
+    level: int # 'severity of the notification'. #TODO_determine: Should this be identical to EvaluationType?
     type: NotificationType # 'type of the notification'
     message: str # 'individual message'
     created: datetime
diff --git a/src/server/BreCal/services/schedule_routines.py b/src/server/BreCal/services/schedule_routines.py
index a36a1fc..2e0be3e 100644
--- a/src/server/BreCal/services/schedule_routines.py
+++ b/src/server/BreCal/services/schedule_routines.py
@@ -4,6 +4,7 @@ from BreCal.schemas import model
 from BreCal.local_db import getPoolConnection
 from BreCal.database.update_database import evaluate_shipcall_state
 from BreCal.database.sql_queries import create_sql_query_shipcall_get
+from BreCal.notifications.notifier import Notifier
 
 import threading
 import schedule
@@ -51,7 +52,7 @@ def add_function_to_schedule__update_shipcalls(interval_in_minutes:int, options:
     return
 
 def add_function_to_schedule__send_notifications(vr, interval_in_minutes:int=10):
-    schedule.every(interval_in_minutes).minutes.do(vr.notifier.send_notifications)
+    schedule.every(interval_in_minutes).minutes.do(Notifier.send_notifications)
     return
 
 
diff --git a/src/server/BreCal/stubs/notification.py b/src/server/BreCal/stubs/notification.py
index 8971a76..b1d42c0 100644
--- a/src/server/BreCal/stubs/notification.py
+++ b/src/server/BreCal/stubs/notification.py
@@ -1,21 +1,21 @@
 import datetime
 from BreCal.stubs import generate_uuid1_int
-from BreCal.schemas.model import Notification
+from BreCal.schemas.model import Notification, NotificationType
 
 
 def get_notification_simple():
     """creates a default notification, where 'created' is now, and modified is now+10 seconds"""
     notification_id = generate_uuid1_int() # uid?
-    times_id = generate_uuid1_int() # uid?
-    level = 10
-    type = 0
+    shipcall_id = 85
+    level = 2
+    type = NotificationType.email
     message = "hello world"
     created = datetime.datetime.now()
     modified = created+datetime.timedelta(seconds=10)
 
     notification = Notification(
         notification_id,
-        times_id,
+        shipcall_id,
         level,
         type,
         message,
diff --git a/src/server/BreCal/validators/validation_rules.py b/src/server/BreCal/validators/validation_rules.py
index 7d5448c..eea5780 100644
--- a/src/server/BreCal/validators/validation_rules.py
+++ b/src/server/BreCal/validators/validation_rules.py
@@ -7,7 +7,7 @@ import datetime
 from BreCal.database.enums import StatusFlags
 from BreCal.validators.validation_rule_functions import ValidationRuleFunctions
 from BreCal.schemas.model import Shipcall
-from BreCal.notifications.notification_functions import Notifier
+from BreCal.notifications.notification_functions import LegacyNotifier
 
 
 class ValidationRules(ValidationRuleFunctions):
@@ -19,7 +19,7 @@ class ValidationRules(ValidationRuleFunctions):
     """
     def __init__(self, sql_handler): # use the entire data that is provided for this query (e.g., json input)
         super().__init__(sql_handler)
-        self.notifier = Notifier()
+        self.notifier = LegacyNotifier()
         return
 
     def evaluate(self, shipcall):
diff --git a/src/server/tests/database/test_sql_queries.py b/src/server/tests/database/test_sql_queries.py
index f490eed..0f3c8c8 100644
--- a/src/server/tests/database/test_sql_queries.py
+++ b/src/server/tests/database/test_sql_queries.py
@@ -3,12 +3,12 @@ import pytest
 import os
 import bcrypt
 import pydapper
-from BreCal import local_db
 from BreCal.database.sql_handler import execute_sql_query_standalone
 from BreCal.database.sql_queries import SQLQuery
 from BreCal.schemas import model
 from BreCal.stubs.user import get_user_simple
 
+from BreCal import local_db
 instance_path = os.path.join(os.path.expanduser('~'), "brecal", "src", "server", "instance", "instance")
 local_db.initPool(os.path.dirname(instance_path), connection_filename="connection_data_local.json")
 
@@ -36,13 +36,10 @@ def test_sql_query_get_user():
     return
 
 def test_sql_get_notifications():
-    import mysql.connector
-
     # unfortunately, there currently is *no* notification in the database. 
-    with pytest.raises(mysql.connector.errors.ProgrammingError, match="Unknown column 'shipcall_id' in 'field list'"):
-        options = {"shipcall_id":222}
-        notifications = execute_sql_query_standalone(query=SQLQuery.get_notifications(), param={"scid" : options["shipcall_id"]}, model=model.Notification.from_query_row)
-        assert all([isinstance(notification,model.Notification) for notification in notifications])
+    options = {"shipcall_id":222}
+    notifications = execute_sql_query_standalone(query=SQLQuery.get_notifications(), param={"scid" : options["shipcall_id"]}, model=model.Notification.from_query_row)
+    assert all([isinstance(notification,model.Notification) for notification in notifications])
     return
 
 def test_sql_get_participants():
@@ -458,7 +455,12 @@ def test_sql__shipcall_post__get_last_insert_id__get_spm__update_participants__v
 
         ### proxy data ###
         # loop across passed participant ids, creating entries for those not present in pdata
-        schemaModel = {'id': new_id, "participants":[{'id': 128, 'participant_id': 2, 'type': 4}, {'id': 129, 'participant_id': 3, 'type': 1}, {'id': 130, 'participant_id': 4, 'type': 2}, {'id': 131, 'participant_id': 6, 'type': 8}]}
+        schemaModel = {'id': new_id, 
+                       "participants":[{'id': 128, 'participant_id': 2, 'type': 4}, 
+                                          {'id': 129, 'participant_id': 3, 'type': 1}, 
+                                          {'id': 130, 'participant_id': 4, 'type': 2}, 
+                                          {'id': 131, 'participant_id': 5, 'type': 8}, 
+                                          {'id': 131, 'participant_id': 6, 'type': 8}]}
 
         # 4.) assign the participants
         for participant_assignment in schemaModel["participants"]:
@@ -522,6 +524,26 @@ def test_sql_query_put_ship_is_identical_to_legacy_query():
     assert query_refactored == query_legacy, f"the refactored code to generate the query must be absolutely identical to the legacy version"
     return
 
+def test_sql_query_notification_post():
+    with pytest.raises(NotImplementedError, match="skeleton"):
+        # not yet defined. Test also not created yet.
+        SQLQuery.get_notification_post()
+    return
+
+def test_sql_query_notification_put():
+    with pytest.raises(NotImplementedError, match="skeleton"):
+        # not yet defined. Test also not created yet.
+        SQLQuery.get_shipcall_put_notification_state()
+    return
+
+def test_sql_query_notifications_get():
+    shipcall_id = 85
+    existing_notifications = execute_sql_query_standalone(query=SQLQuery.get_notifications(), param={"scid" : shipcall_id}, model=model.Notification, command_type="query")
+    if len(existing_notifications)>0:
+        assert isinstance(existing_notifications[0], model.Notification), f"returned an incorrect data model. Should have been model.Notification. Found: {type(existing_notifications)} --- {existing_notifications}"
+    return
+
+
 
 
 #schemas = execute_sql_query_standalone(query=SQLQuery.get_berth(), param={})
diff --git a/src/server/tests/notifications/__init__.py b/src/server/tests/notifications/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/src/server/tests/notifications/test_notifier.py b/src/server/tests/notifications/test_notifier.py
new file mode 100644
index 0000000..37bee02
--- /dev/null
+++ b/src/server/tests/notifications/test_notifier.py
@@ -0,0 +1,256 @@
+import pytest
+from BreCal.notifications.notifier import Notifier
+from BreCal.schemas.model import Notification
+
+from BreCal.database.sql_queries import SQLQuery
+from BreCal.database.sql_handler import execute_sql_query_standalone
+from BreCal.schemas import model
+from BreCal.stubs.user import get_user_simple
+
+import os
+from BreCal import local_db
+instance_path = os.path.join(os.path.expanduser('~'), "brecal", "src", "server", "instance", "instance")
+local_db.initPool(os.path.dirname(instance_path), connection_filename="connection_data_local.json")
+
+@pytest.fixture(scope="session")
+def default_ids():
+    # #TODO: use a shipcall_id, where a notification actually exists. Otherwise, this is not testable..
+    shipcall_id = 85
+    user_id = 29
+    return locals()
+
+
+def test_notifier_send_notifications():
+    """
+    the Notifier's .send_notifications() method will be called by the schedule module as part of a routine.
+    The method shall work without issues or outside arguments.
+    """
+    with pytest.raises(NotImplementedError, match="skeleton"):
+        Notifier.send_notifications(is_test=True)
+    return
+
+def test_notifier_create_notification(default_ids):
+    shipcall_id, user_id = default_ids["shipcall_id"], default_ids["user_id"]
+    old_state, new_state = model.EvaluationType(1),model.EvaluationType(3)
+    user = Notifier.get_user(user_id)
+    user.notify_email = 1
+    user.notify_popup = 1
+    user.notify_signal = 1
+    user.notify_whatsapp = 1
+    
+    with pytest.raises(NotImplementedError, match="skeleton"):
+        notification = Notifier.publish(shipcall_id, old_state, new_state, user, update_database=False)
+        assert isinstance(notification, Notification)
+    return
+
+def test_notifier_create_notification_update_database(default_ids):
+    # generate a shipcall
+    # get the shipcall
+    # create notifications
+    
+    shipcall_id, user_id = default_ids["shipcall_id"], default_ids["user_id"]
+    old_state, new_state = model.EvaluationType(1),model.EvaluationType(3)
+    user = Notifier.get_user(user_id)
+    user.notify_email = 1
+    user.notify_popup = 1
+    user.notify_signal = 1
+    user.notify_whatsapp = 1
+    
+    with pytest.raises(NotImplementedError, match="skeleton"):
+        notification = Notifier.publish(shipcall_id, old_state, new_state, user, update_database=True)
+
+        # #TODO: apply GetNotifications(*args) and identify, whether the notification exists now. Use an obvious 'message' to identify pytest creations.
+    return
+
+def test_notifier_get_user(default_ids):
+    user_id = default_ids["user_id"]
+    user_data = get_user_simple().__dict__
+    user_data["id"] = user_id
+    user = Notifier.get_user(user_data["id"])
+
+    assert hasattr(user, "notify_email")
+    assert hasattr(user, "notify_popup")
+    assert hasattr(user, "notify_whatsapp")
+    assert hasattr(user, "notify_signal")
+    return
+
+def test_notification_type():
+    """this pytest serves as a warning method to inform the developers, once novel NotificationType s have been included."""
+    members = [key for key in model.NotificationType.__members__]
+    expected_member_count = 3
+    assert len(members)==expected_member_count, f"the BreCal.model.NotificationType has been changed. Initially, there were only {expected_member_count} members. Now that there are more members, the Notifier.build_notification_type_list and its pytest can be updated. This pytest shall also be updated!"
+    return
+
+def test_notifier_build_notification_type_list(default_ids):
+    user_id = default_ids["user_id"]
+    user = Notifier.get_user(user_id)
+    user.notify_email = 1
+    user.notify_popup = 1
+    user.notify_whatsapp = 1
+    user.notify_signal = 1
+
+    notification_type_list = Notifier.build_notification_type_list(user)
+    assert len(notification_type_list) == 4, f"there must be n=4 notifications, as there are fours types of notifications."
+    assert len([ntype for ntype in notification_type_list if ntype==model.NotificationType.email])==1, f"the EMAIL notification instruction was not created"
+    assert len([ntype for ntype in notification_type_list if ntype==model.NotificationType.push])==1, f"the POPUP/PUSH notification instruction was not created"
+    assert len([ntype for ntype in notification_type_list if ntype==model.NotificationType.undefined])==2, f"there must currently be two notifications, which have an undefined type (SIGNAL and WHATSAPP)"
+    return
+
+def test_notifier_build_notification_type_list__behaves_as_expected(default_ids):
+    user_id = default_ids["user_id"]
+    user = Notifier.get_user(user_id)
+    # only email
+    user.notify_email = 1
+    user.notify_popup = 0
+    user.notify_whatsapp = 0
+    user.notify_signal = 0
+
+    notification_type_list = Notifier.build_notification_type_list(user)
+    assert len(notification_type_list) == 1
+    assert int(notification_type_list[0])==int(model.NotificationType.email), f"should've returned email, but did not"
+
+    # only popup
+    user.notify_email = 0
+    user.notify_popup = 1
+    user.notify_whatsapp = 0
+    user.notify_signal = 0
+
+    notification_type_list = Notifier.build_notification_type_list(user)
+    assert len(notification_type_list) == 1
+    assert int(notification_type_list[0])==int(model.NotificationType.push), f"should've returned push, but did not"
+
+    # only whatsapp
+    user.notify_email = 0
+    user.notify_popup = 0
+    user.notify_whatsapp = 1
+    user.notify_signal = 0
+
+    notification_type_list = Notifier.build_notification_type_list(user)
+    assert len(notification_type_list) == 1
+    # #TODO: adapt the NotificationType.undefined once a data model exists for whatsapp
+    assert int(notification_type_list[0])==int(model.NotificationType.undefined), f"should've returned whatsapp, but did not"
+
+    # only signal
+    user.notify_email = 0
+    user.notify_popup = 0
+    user.notify_whatsapp = 0
+    user.notify_signal = 1
+
+    notification_type_list = Notifier.build_notification_type_list(user)
+    assert len(notification_type_list) == 1
+    # #TODO: adapt the NotificationType.undefined once a data model exists for signal
+    assert int(notification_type_list[0])==int(model.NotificationType.undefined), f"should've returned signal, but did not"
+    return
+
+def test_notifier_get_shipcall():
+    shipcall_id = 85
+    shipcall = Notifier.get_shipcall(shipcall_id=shipcall_id)
+    assert shipcall.id==85
+    assert shipcall.arrival_berth_id == 194
+    return
+
+def test_notifier_get_existing_notifications(default_ids):
+    shipcall_id = default_ids["shipcall_id"]
+    existing_notifications = Notifier.get_existing_notifications(shipcall_id)
+
+    assert isinstance(existing_notifications, list)
+    if len(existing_notifications)>0:
+        assert all([isinstance(existing_notification, model.Notification) for existing_notification in existing_notifications])
+    return
+
+def test_notifier_check_notification_type_and_level_exists(default_ids):
+    """this method has been deprecated, because the conceptual-logic does not add up."""
+    with pytest.raises(Exception, match="deprecated"):
+        shipcall_id = default_ids["shipcall_id"]
+
+        from BreCal.stubs.notification import get_notification_simple
+        notification = get_notification_simple().__dict__
+        notification["shipcall_id"] = shipcall_id
+        level = 2
+        existing_notifications = Notifier.get_existing_notifications(shipcall_id=notification.get("shipcall_id"))
+        exists = Notifier.check_notification_type_and_level_exists(shipcall_id=shipcall_id, notification_type=notification.get("type"), level=level, existing_notifications=existing_notifications)
+        # assert exists==True, f"for the given notification, the method should return, that the notification already exists."
+    return
+
+def test_notifier_check_higher_severity():
+    """
+    Checks all possible combinations of model.EvaluationType within Notifier.check_higher_severity
+    It should prove, that a boolean True is only returned, when the severity grows. In particular,
+            undefined or green -> yellow
+            undefined or green -> red
+            yellow -> red
+    """
+    # [FALSE] cases: should not trigger the creation of a Notification
+    old_state, new_state = model.EvaluationType.green, model.EvaluationType.undefined
+    assert not Notifier.check_higher_severity(old_state, new_state), f"this case should not create a Notification!"
+
+    old_state, new_state = model.EvaluationType.yellow, model.EvaluationType.green
+    assert not Notifier.check_higher_severity(old_state, new_state), f"this case should not create a Notification!"
+
+    old_state, new_state = model.EvaluationType.yellow, model.EvaluationType.undefined
+    assert not Notifier.check_higher_severity(old_state, new_state), f"this case should not create a Notification!"
+
+    old_state, new_state = model.EvaluationType.red, model.EvaluationType.yellow
+    assert not Notifier.check_higher_severity(old_state, new_state), f"this case should not create a Notification!"
+
+    old_state, new_state = model.EvaluationType.red, model.EvaluationType.green
+    assert not Notifier.check_higher_severity(old_state, new_state), f"this case should not create a Notification!"
+
+    old_state, new_state = model.EvaluationType.red, model.EvaluationType.undefined
+    assert not Notifier.check_higher_severity(old_state, new_state), f"this case should not create a Notification!"
+
+    old_state, new_state = model.EvaluationType.undefined, model.EvaluationType.green
+    assert not Notifier.check_higher_severity(old_state, new_state), f"this case should not create a Notification!"
+
+
+    # [FALSE] SAME EVALUATION as before
+    old_state, new_state = model.EvaluationType.undefined, model.EvaluationType.undefined
+    assert not Notifier.check_higher_severity(old_state, new_state), f"this case should not create a Notification!"
+
+    old_state, new_state = model.EvaluationType.green, model.EvaluationType.green
+    assert not Notifier.check_higher_severity(old_state, new_state), f"this case should not create a Notification!"
+
+    old_state, new_state = model.EvaluationType.yellow, model.EvaluationType.yellow
+    assert not Notifier.check_higher_severity(old_state, new_state), f"this case should not create a Notification!"
+
+    old_state, new_state = model.EvaluationType.red, model.EvaluationType.red
+    assert not Notifier.check_higher_severity(old_state, new_state), f"this case should not create a Notification!"
+
+    # [TRUE] cases: should then trigger the creation of a Notification
+    old_state, new_state = model.EvaluationType.green, model.EvaluationType.yellow
+    assert Notifier.check_higher_severity(old_state, new_state), f"this case should create a Notification, but the method did not recognize it."
+
+    old_state, new_state = model.EvaluationType.yellow, model.EvaluationType.red
+    assert Notifier.check_higher_severity(old_state, new_state), f"this case should create a Notification, but the method did not recognize it."
+    
+    old_state, new_state = model.EvaluationType.green, model.EvaluationType.red
+    assert Notifier.check_higher_severity(old_state, new_state), f"this case should create a Notification, but the method did not recognize it."
+    
+    old_state, new_state = model.EvaluationType.undefined, model.EvaluationType.yellow
+    assert Notifier.check_higher_severity(old_state, new_state), f"this case should create a Notification, but the method did not recognize it."
+    
+    old_state, new_state = model.EvaluationType.undefined, model.EvaluationType.red
+    assert Notifier.check_higher_severity(old_state, new_state), f"this case should create a Notification, but the method did not recognize it."
+    return
+
+def test_notifier_loop_generate_notification_message_by_type(default_ids):
+    user_id = default_ids["user_id"]
+    user = execute_sql_query_standalone(query=SQLQuery.get_user_by_id(), param={"id" : user_id}, model=model.User, command_type="single")
+
+    # enable all notification types
+    user.notify_email=1
+    user.notify_whatsapp=1
+    user.notify_signal=1
+    user.notify_popup=1
+
+    evaluation_message = "abc"
+
+    with pytest.raises(NotImplementedError, match="skeleton"):
+        # create a list of notification types and create a message for each of them
+        notification_type_list = Notifier.build_notification_type_list(user)
+        for notification_type in notification_type_list:
+            message = Notifier.generate_notification_message_by_type(notification_type, evaluation_message, user)
+            assert isinstance(message, str), f"Message must be a string. Found: {type(message)} --- {message}"
+
+        assert not evaluation_message=="abc", f"#TODO_metz: lazy development. have to update the message body"
+    return