diff --git a/app/admin.py b/app/admin.py
index 819b99d..7712358 100644
--- a/app/admin.py
+++ b/app/admin.py
@@ -1,12 +1,14 @@
 import flask_login as login
+from flask import Flask
 from flask_admin import Admin
 from flask_admin.contrib.sqla import ModelView
+from flask_sqlalchemy import SQLAlchemy
 
 from models import Location, Order, OrderItem, Product, User
 
 
 class ModelBaseView(ModelView):
-    def is_accessible(self):
+    def is_accessible(self) -> bool:
         if login.current_user.is_anonymous():
             return False
 
@@ -29,7 +31,7 @@ class LocationAdminModel(ModelBaseView):
     form_columns = ("name", "address", "website", "telephone")
 
 
-def init_admin(app, db):
+def init_admin(app: Flask, db: SQLAlchemy) -> None:
     admin = Admin(app, name="Haldis", url="/admin", template_mode="bootstrap3")
 
     admin.add_view(UserAdminModel(User, db.session))
diff --git a/app/app.py b/app/app.py
index e1674d5..8e6c063 100644
--- a/app/app.py
+++ b/app/app.py
@@ -1,4 +1,5 @@
 import logging
+import typing
 from datetime import datetime
 from logging.handlers import TimedRotatingFileHandler
 
@@ -19,7 +20,7 @@
 from zeus import init_oauth
 
 
-def create_app():
+def create_app() -> Manager:
     app = Flask(__name__)
 
     # Load the config file
@@ -34,7 +35,7 @@ def create_app():
     return manager
 
 
-def register_plugins(app, debug: bool):
+def register_plugins(app: Flask, debug: bool) -> Manager:
     # Register Airbrake and enable the logrotation
     if not app.debug:
         timedFileHandler = TimedRotatingFileHandler(
@@ -96,17 +97,17 @@ def register_plugins(app, debug: bool):
     return manager
 
 
-def add_handlers(app):
+def add_handlers(app: Flask) -> None:
     @app.errorhandler(404)
-    def handle404(e):
+    def handle404(e) -> typing.Tuple[str, int]:
         return render_template("errors/404.html"), 404
 
     @app.errorhandler(401)
-    def handle401(e):
+    def handle401(e) -> typing.Tuple[str, int]:
         return render_template("errors/401.html"), 401
 
 
-def add_routes(application):
+def add_routes(application: Flask) -> None:
     # import views  # TODO convert to blueprint
     # import views.stats  # TODO convert to blueprint
 
@@ -127,9 +128,9 @@ def add_routes(application):
         application.register_blueprint(debug_bp, url_prefix="/debug")
 
 
-def add_template_filters(app):
+def add_template_filters(app: Flask) -> None:
     @app.template_filter("countdown")
-    def countdown(value, only_positive=True, show_text=True):
+    def countdown(value, only_positive: bool = True, show_text: bool = True) -> str:
         delta = value - datetime.now()
         if delta.total_seconds() < 0 and only_positive:
             return "closed"
@@ -141,11 +142,11 @@ def countdown(value, only_positive=True, show_text=True):
         return time
 
     @app.template_filter("year")
-    def current_year(value):
+    def current_year(value: typing.Any) -> str:
         return str(datetime.now().year)
 
     @app.template_filter("euro")
-    def euro(value):
+    def euro(value: int) -> None:
         euro_string(value)
 
 
diff --git a/app/database/add_admins.py b/app/database/add_admins.py
index c3dff1f..cb385c7 100644
--- a/app/database/add_admins.py
+++ b/app/database/add_admins.py
@@ -2,7 +2,7 @@
 from models import User
 
 
-def add():
+def add() -> None:
     feli = User()
     feli.configure("feliciaan", True, 0)
     db.session.add(feli)
diff --git a/app/database/add_fitchen.py b/app/database/add_fitchen.py
index 8e7ff9b..b9a885e 100644
--- a/app/database/add_fitchen.py
+++ b/app/database/add_fitchen.py
@@ -1,6 +1,5 @@
-from models import Location, Product
 from app import db
-
+from models import Location, Product
 
 menuitems = [
     "Spicy Chicken",
@@ -23,7 +22,7 @@
 pricedict = {"Small": 799, "Medium": 999, "Large": 1199}
 
 
-def add():
+def add() -> None:
     simpizza = Location()
     simpizza.configure("Fitchen", "?", "?", "https://www.fitchen.be/")
     db.session.add(simpizza)
diff --git a/app/database/add_oceans_garden.py b/app/database/add_oceans_garden.py
index 0954fc5..fb293ef 100644
--- a/app/database/add_oceans_garden.py
+++ b/app/database/add_oceans_garden.py
@@ -1,7 +1,7 @@
-from models import Location, Product
-from app import db
 from itertools import product
 
+from app import db
+from models import Location, Product
 
 zetmelen = ["Nasi", "Bami"]
 vlezen = ["Rundsvlees", "Varkensvlees", "Kippenstukkjes"]
@@ -29,7 +29,7 @@
 ]
 
 
-def add():
+def add() -> None:
     chinees = Location()
     chinees.configure(
         "Oceans's Garden",
@@ -39,12 +39,12 @@ def add():
     )
     db.session.add(chinees)
 
-    def chinees_create_entry(name):
+    def chinees_create_entry(name) -> None:
         entry = Product()
         entry.configure(chinees, name, 550)
         db.session.add(entry)
 
-    def chinees_create_regulat(zetmeel, vlees="", saus=""):
+    def chinees_create_regulat(zetmeel, vlees="", saus="") -> None:
         chinees_create_entry("{} {} {}".format(zetmeel, vlees, saus).rstrip())
 
     for z, v, s in product(zetmelen, vlezen, sauzen):
diff --git a/app/database/add_primadonna.py b/app/database/add_primadonna.py
index 28aa564..5bbb3c4 100644
--- a/app/database/add_primadonna.py
+++ b/app/database/add_primadonna.py
@@ -1,5 +1,5 @@
-from models import Location, Product
 from app import db
+from models import Location, Product
 
 
 def add():
@@ -46,7 +46,7 @@ def add():
 }
 
 
-def addTA():
+def addTA() -> None:
     primadonna_takeaway = Location()
     primadonna_takeaway.configure(
         "Primadonna (takeaway laten bezorgen)",
@@ -101,7 +101,7 @@ def addTA():
 }
 
 
-def addAfhalen():
+def addAfhalen() -> None:
     primadonna_afhalen = Location()
     primadonna_afhalen.configure(
         "Primadonna (bellen en afhalen)",
diff --git a/app/database/add_simpizza.py b/app/database/add_simpizza.py
index e653195..77a6c0f 100644
--- a/app/database/add_simpizza.py
+++ b/app/database/add_simpizza.py
@@ -1,6 +1,5 @@
-from models import Location, Product
 from app import db
-
+from models import Location, Product
 
 pizzas = [
     "Bolognese de luxe",
@@ -33,7 +32,7 @@
 ]
 
 
-def add():
+def add() -> None:
     simpizza = Location()
     simpizza.configure(
         "Sim-pizza",
diff --git a/app/database/add_stefanos.py b/app/database/add_stefanos.py
index 35f7a38..9868d29 100644
--- a/app/database/add_stefanos.py
+++ b/app/database/add_stefanos.py
@@ -1,5 +1,5 @@
-from models import Location, Product
 from app import db
+from models import Location, Product
 
 bickies = {
     "Bicky Burger Original": 330,
@@ -11,7 +11,7 @@
     "Bicky Veggie": 350,
 }
 
-saus = {
+sauskes = {
     "american": 70,
     "andalouse": 70,
     "bicky saus": 70,
@@ -100,7 +100,7 @@
 data = [special_bickies, specials, vlezekes, friet]
 
 
-def add():
+def add() -> None:
     stefanos = Location()
     stefanos.configure(
         "Stefano's Place",
@@ -127,7 +127,7 @@ def add():
             db.session.add(item)
 
     # saus in een potteke bestellen is 10 cent extra
-    for name, price in saus.items():
+    for name, price in sauskes.items():
         saus = Product()
         saus.configure(stefanos, name, price)
         db.session.add(saus)
diff --git a/app/database/create_database.py b/app/database/create_database.py
index 244e212..cdadd2b 100644
--- a/app/database/create_database.py
+++ b/app/database/create_database.py
@@ -1,6 +1,9 @@
+import add_admins
+import add_fitchen
+import add_oceans_garden
+import add_primadonna
+import add_simpizza
 from app import db
-import add_oceans_garden, add_admins, add_simpizza, add_primadonna, add_fitchen
-
 
 entry_sets = {
     "Admins": add_admins.add,
@@ -15,23 +18,23 @@
 
 
 # Commit all the things
-def commit():
+def commit() -> None:
     db.session.commit()
     print("Committing successful")
 
 
-def check_if_overwrite():
+def check_if_overwrite() -> bool:
     answer = input("Do you want to overwrite the previous database? (y/N) ")
     return answer in yes
 
 
-def add_all():
+def add_all() -> None:
     for entry_set in entry_sets.keys():
         print("Adding {}.".format(entry_set))
         entry_sets[entry_set]()
 
 
-def recreate_from_scratch():
+def recreate_from_scratch() -> None:
     confirmation = "Are you very very sure? (Will delete previous entries!) (y/N) "
     check = "I acknowledge any repercussions!"
     if input(confirmation) in yes and input("Type: '{}' ".format(check)) == check:
@@ -41,10 +44,10 @@ def recreate_from_scratch():
         add_to_current()
 
 
-def add_to_current():
+def add_to_current() -> None:
     available = [entry_set for entry_set in entry_sets]
 
-    def add_numbers():
+    def add_numbers() -> str:
         return "  ".join(
             ["{}({}), ".format(loc, i) for i, loc in enumerate(available)]
         ).rstrip(", ")
@@ -59,17 +62,17 @@ def add_numbers():
             available = []
         elif answer == "C":
             pass
-        elif answer in [str(x) for x in range(len(available))]:
-            answer = int(answer)
-            print("Adding {}.".format(available[answer]))
-            entry_sets[str(available[answer])]()
-            del available[answer]
+        elif answer.isnumeric() and answer in [str(x) for x in range(len(available))]:
+            answer_index = int(answer)
+            print("Adding {}.".format(available[answer_index]))
+            entry_sets[str(available[answer_index])]()
+            del available[answer_index]
         else:
             print("Not a valid answer.")
     print("Thank you for adding, come again!")
 
 
-def init():
+def init() -> None:
     print("Database modification script!")
     print("=============================\n\n")
     if check_if_overwrite():
diff --git a/app/fatmodels.py b/app/fatmodels.py
index f4c4c53..79eac01 100644
--- a/app/fatmodels.py
+++ b/app/fatmodels.py
@@ -1,3 +1,5 @@
+import typing
+
 from sqlalchemy.sql import desc, func
 
 from models import Location, Order, OrderItem, Product, User
@@ -42,7 +44,7 @@ class FatOrderItem(OrderItem, FatModel):
 
 class FatProduct(Product, FatModel):
     @classmethod
-    def top4(cls):
+    def top4(cls) -> None:
         top4 = (
             OrderItem.query.join(Product)
             .join(Location)
diff --git a/app/forms.py b/app/forms.py
index a41c188..4003944 100644
--- a/app/forms.py
+++ b/app/forms.py
@@ -3,7 +3,8 @@
 from flask import session
 from flask_login import current_user
 from flask_wtf import FlaskForm as Form
-from wtforms import DateTimeField, SelectField, StringField, SubmitField, validators
+from wtforms import (DateTimeField, SelectField, StringField, SubmitField,
+                     validators)
 
 from models import Location, User
 from utils import euro_string
@@ -20,7 +21,7 @@ class OrderForm(Form):
     stoptime = DateTimeField("Stoptime", format="%d-%m-%Y %H:%M")
     submit_button = SubmitField("Submit")
 
-    def populate(self):
+    def populate(self) -> None:
         if current_user.is_admin():
             self.courrier_id.choices = [(0, None)] + [
                 (u.id, u.username) for u in User.query.order_by("username")
@@ -42,7 +43,7 @@ class OrderItemForm(Form):
     extra = StringField("Extra")
     submit_button = SubmitField("Submit")
 
-    def populate(self, location):
+    def populate(self, location: Location) -> None:
         self.product_id.choices = [
             (i.id, (i.name + ": " + euro_string(i.price))) for i in location.products
         ]
@@ -51,12 +52,12 @@ def populate(self, location):
 class AnonOrderItemForm(OrderItemForm):
     name = StringField("Name", validators=[validators.required()])
 
-    def populate(self, location):
+    def populate(self, location: Location) -> None:
         OrderItemForm.populate(self, location)
         if self.name.data is None:
             self.name.data = session.get("anon_name", None)
 
-    def validate(self):
+    def validate(self) -> bool:
         rv = OrderForm.validate(self)
         if not rv:
             return False
diff --git a/app/login.py b/app/login.py
index 27c2e8a..c50b245 100644
--- a/app/login.py
+++ b/app/login.py
@@ -1,6 +1,6 @@
-from flask import abort, Blueprint
-from flask import redirect, session, url_for
+from flask import Blueprint, abort, redirect, session, url_for
 from flask_login import current_user, logout_user
+from werkzeug.wrappers import Response
 
 from models import User
 from zeus import zeus_login
@@ -8,9 +8,9 @@
 auth_bp = Blueprint("auth_bp", __name__)
 
 
-def init_login(app):
+def init_login(app) -> None:
     @app.login_manager.user_loader
-    def load_user(userid):
+    def load_user(userid) -> User:
         return User.query.filter_by(id=userid).first()
 
 
@@ -20,13 +20,13 @@ def login():
 
 
 @auth_bp.route("/logout")
-def logout():
+def logout() -> Response:
     if "zeus_token" in session:
         session.pop("zeus_token", None)
     logout_user()
     return redirect(url_for("general_bp.home"))
 
 
-def before_request():
+def before_request() -> None:
     if current_user.is_anonymous() or not current_user.is_allowed():
         abort(401)
diff --git a/app/migrations/env.py b/app/migrations/env.py
index 6b2907b..f416a43 100644
--- a/app/migrations/env.py
+++ b/app/migrations/env.py
@@ -1,7 +1,14 @@
 from __future__ import with_statement
+
+from logging.config import fileConfig
+
 from alembic import context
+# add your model's MetaData object here
+# for 'autogenerate' support
+# from myapp import mymodel
+# target_metadata = mymodel.Base.metadata
+from flask import current_app
 from sqlalchemy import engine_from_config, pool
-from logging.config import fileConfig
 
 # this is the Alembic Config object, which provides
 # access to the values within the .ini file in use.
@@ -11,11 +18,6 @@
 # This line sets up loggers basically.
 fileConfig(config.config_file_name)
 
-# add your model's MetaData object here
-# for 'autogenerate' support
-# from myapp import mymodel
-# target_metadata = mymodel.Base.metadata
-from flask import current_app
 
 config.set_main_option(
     "sqlalchemy.url", current_app.config.get("SQLALCHEMY_DATABASE_URI")
diff --git a/app/migrations/versions/150252c1cdb1_.py b/app/migrations/versions/150252c1cdb1_.py
index 62a6099..753b70d 100644
--- a/app/migrations/versions/150252c1cdb1_.py
+++ b/app/migrations/versions/150252c1cdb1_.py
@@ -10,8 +10,8 @@
 revision = "150252c1cdb1"
 down_revision = None
 
-from alembic import op
 import sqlalchemy as sa
+from alembic import op
 
 
 def upgrade():
diff --git a/app/models/anonymous_user.py b/app/models/anonymous_user.py
index d82abd9..76f99f7 100644
--- a/app/models/anonymous_user.py
+++ b/app/models/anonymous_user.py
@@ -1,17 +1,17 @@
 class AnonymouseUser:
     id = None
 
-    def is_active(self):
+    def is_active(self) -> bool:
         return False
 
-    def is_authenticated(self):
+    def is_authenticated(self) -> bool:
         return False
 
-    def is_anonymous(self):
+    def is_anonymous(self) -> bool:
         return True
 
-    def is_admin(self):
+    def is_admin(self) -> bool:
         return False
 
-    def get_id(self):
+    def get_id(self) -> None:
         return None
diff --git a/app/models/location.py b/app/models/location.py
index 73946e7..539e21d 100644
--- a/app/models/location.py
+++ b/app/models/location.py
@@ -1,3 +1,5 @@
+import typing
+
 from models import db
 
 
@@ -10,11 +12,13 @@ class Location(db.Model):
     products = db.relationship("Product", backref="location", lazy="dynamic")
     orders = db.relationship("Order", backref="location", lazy="dynamic")
 
-    def configure(self, name, address, telephone, website):
+    def configure(
+        self, name: str, address: str, telephone: typing.Optional[str], website: str
+    ) -> None:
         self.name = name
         self.address = address
         self.website = website
         self.telephone = telephone
 
-    def __repr__(self):
+    def __repr__(self) -> str:
         return "%s" % (self.name)
diff --git a/app/models/order.py b/app/models/order.py
index 0c804ec..44718fd 100644
--- a/app/models/order.py
+++ b/app/models/order.py
@@ -1,6 +1,8 @@
+import typing
 from datetime import datetime
 
 from .database import db
+from .location import Location
 from .user import User
 
 
@@ -13,20 +15,26 @@ class Order(db.Model):
     public = db.Column(db.Boolean, default=True)
     items = db.relationship("OrderItem", backref="order", lazy="dynamic")
 
-    def configure(self, courrier, location, starttime, stoptime):
+    def configure(
+        self,
+        courrier: User,
+        location: Location,
+        starttime: db.DateTime,
+        stoptime: db.DateTime,
+    ) -> None:
         self.courrier = courrier
         self.location = location
         self.starttime = starttime
         self.stoptime = stoptime
 
-    def __repr__(self):
+    def __repr__(self) -> str:
         if self.location:
             return "Order %d @ %s" % (self.id, self.location.name or "None")
         else:
             return "Order %d" % (self.id)
 
-    def group_by_user(self):
-        group = dict()
+    def group_by_user(self) -> typing.Dict[str, typing.Any]:
+        group: typing.Dict[str, typing.Any] = dict()
         for item in self.items:
             user = group.get(item.get_name(), dict())
             user["total"] = user.get("total", 0) + item.product.price
@@ -39,8 +47,8 @@ def group_by_user(self):
 
         return group
 
-    def group_by_product(self):
-        group = dict()
+    def group_by_product(self) -> typing.Dict[str, typing.Any]:
+        group: typing.Dict[str, typing.Any] = dict()
         for item in self.items:
             product = group.get(item.product.name, dict())
             product["count"] = product.get("count", 0) + 1
@@ -50,7 +58,7 @@ def group_by_product(self):
 
         return group
 
-    def can_close(self, user_id):
+    def can_close(self, user_id: int) -> bool:
         if self.stoptime and self.stoptime < datetime.now():
             return False
         user = None
diff --git a/app/models/orderitem.py b/app/models/orderitem.py
index 0ea982e..d699a90 100644
--- a/app/models/orderitem.py
+++ b/app/models/orderitem.py
@@ -1,6 +1,8 @@
 from datetime import datetime
 
 from .database import db
+from .order import Order
+from .product import Product
 from .user import User
 
 
@@ -17,17 +19,17 @@ class OrderItem(db.Model):
     extra = db.Column(db.String(254), nullable=True)
     name = db.Column(db.String(120))
 
-    def configure(self, user, order, product):
+    def configure(self, user: User, order: Order, product: Product) -> None:
         self.user = user
         self.order = order
         self.product = product
 
-    def get_name(self):
+    def get_name(self) -> str:
         if self.user_id is not None and self.user_id > 0:
             return self.user.username
         return self.name
 
-    def __repr__(self):
+    def __repr__(self) -> str:
         product_name = None
         if self.product:
             product_name = self.product.name
@@ -37,7 +39,7 @@ def __repr__(self):
             product_name or "None",
         )
 
-    def can_delete(self, order_id, user_id, name):
+    def can_delete(self, order_id: int, user_id: int, name: str) -> bool:
         if int(self.order_id) != int(order_id):
             return False
         if self.order.stoptime and self.order.stoptime < datetime.now():
diff --git a/app/models/product.py b/app/models/product.py
index 21e4008..7e8e1a7 100644
--- a/app/models/product.py
+++ b/app/models/product.py
@@ -1,5 +1,7 @@
 from models import db
 
+from .location import Location
+
 
 class Product(db.Model):
     id = db.Column(db.Integer, primary_key=True)
@@ -8,12 +10,12 @@ class Product(db.Model):
     price = db.Column(db.Integer, nullable=False)
     orderItems = db.relationship("OrderItem", backref="product", lazy="dynamic")
 
-    def configure(self, location, name, price):
+    def configure(self, location: Location, name: str, price: int) -> None:
         self.location = location
         self.name = name
         self.price = price
 
-    def __repr__(self):
+    def __repr__(self) -> str:
         return "%s (€%d)from %s" % (
             self.name,
             self.price / 100,
diff --git a/app/models/user.py b/app/models/user.py
index 93362d1..4ed2fe8 100644
--- a/app/models/user.py
+++ b/app/models/user.py
@@ -14,25 +14,25 @@ class User(db.Model):
     )
     orderItems = db.relationship("OrderItem", backref="user", lazy="dynamic")
 
-    def configure(self, username, admin, bias):
+    def configure(self, username: str, admin: bool, bias: int) -> None:
         self.username = username
         self.admin = admin
         self.bias = bias
 
-    def is_authenticated(self):
+    def is_authenticated(self) -> bool:
         return True
 
-    def is_active(self):
+    def is_active(self) -> bool:
         return True
 
-    def is_admin(self):
+    def is_admin(self) -> bool:
         return self.admin
 
-    def is_anonymous(self):
+    def is_anonymous(self) -> bool:
         return False
 
-    def get_id(self):
+    def get_id(self) -> str:
         return str(self.id)
 
-    def __repr__(self):
+    def __repr__(self) -> str:
         return "%s" % self.username
diff --git a/app/notification.py b/app/notification.py
index 2fc8cbc..be20c3c 100644
--- a/app/notification.py
+++ b/app/notification.py
@@ -7,7 +7,7 @@
 from flask import url_for
 
 
-def post_order_to_webhook(order_item):
+def post_order_to_webhook(order_item) -> None:
     message = ""
     if order_item.courrier is not None:
         message = "<!channel|@channel> {3} is going to {1}, order <{0}|here>! Deadline in {2} minutes!".format(
@@ -27,14 +27,14 @@ def post_order_to_webhook(order_item):
 
 
 class WebhookSenderThread(Thread):
-    def __init__(self, message):
+    def __init__(self, message: str) -> None:
         super(WebhookSenderThread, self).__init__()
         self.message = message
 
-    def run(self):
+    def run(self) -> None:
         self.slack_webhook()
 
-    def slack_webhook(self):
+    def slack_webhook(self) -> None:
         js = json.dumps({"text": self.message})
         url = app.config["SLACK_WEBHOOK"]
         if len(url) > 0:
@@ -43,7 +43,7 @@ def slack_webhook(self):
             app.logger.info(str(js))
 
 
-def remaining_minutes(value):
+def remaining_minutes(value) -> str:
     delta = value - datetime.now()
     if delta.total_seconds() < 0:
         return "0"
diff --git a/app/utils.py b/app/utils.py
index 0c456ce..1584117 100644
--- a/app/utils.py
+++ b/app/utils.py
@@ -1,4 +1,4 @@
-def euro_string(value):
+def euro_string(value: int) -> str:
     """
     Convert cents to string formatted euro
     """
diff --git a/app/views/debug.py b/app/views/debug.py
index 84dd545..96177e7 100644
--- a/app/views/debug.py
+++ b/app/views/debug.py
@@ -8,7 +8,7 @@
 
 @debug_bp.route("/routes")
 @login_required
-def list_routes():
+def list_routes() -> str:
     import urllib
 
     output = []
diff --git a/app/views/general.py b/app/views/general.py
index d1ade12..9617ec9 100644
--- a/app/views/general.py
+++ b/app/views/general.py
@@ -7,7 +7,6 @@
 from flask_login import login_required
 
 from models import Location, Order
-
 # import views
 from views.order import get_orders
 
@@ -15,7 +14,7 @@
 
 
 @general_bp.route("/")
-def home():
+def home() -> str:
     prev_day = datetime.now() - timedelta(days=1)
     recently_closed = get_orders(
         ((Order.stoptime > prev_day) & (Order.stoptime < datetime.now()))
@@ -27,19 +26,19 @@ def home():
 
 @general_bp.route("/map", defaults={"id": None})
 @general_bp.route("/map/<int:id>")
-def map(id):
+def map(id) -> str:
     locs = Location.query.order_by("name")
     return render_template("maps.html", locations=locs)
 
 
 @general_bp.route("/location")
-def locations():
+def locations() -> str:
     locs = Location.query.order_by("name")
     return render_template("locations.html", locations=locs)
 
 
 @general_bp.route("/location/<int:id>")
-def location(id):
+def location(id) -> str:
     loc = Location.query.filter(Location.id == id).first()
     if loc is None:
         abort(404)
@@ -47,27 +46,27 @@ def location(id):
 
 
 @general_bp.route("/about/")
-def about():
+def about() -> str:
     return render_template("about.html")
 
 
 @general_bp.route("/profile/")
 @login_required
-def profile():
+def profile() -> str:
     return render_template("profile.html")
 
 
 @general_bp.route("/favicon.ico")
-def favicon():
+def favicon() -> str:
     if len(get_orders((Order.stoptime > datetime.now()))) == 0:
         return send_from_directory(
-            os.path.join(app.root_path, "static"),
+            os.path.join(str(app.root_path), "static"),
             "favicon.ico",
             mimetype="image/x-icon",
         )
     else:
         return send_from_directory(
-            os.path.join(app.root_path, "static"),
+            os.path.join(str(app.root_path), "static"),
             "favicon_orange.ico",
             mimetype="image/x-icon",
         )
diff --git a/app/views/order.py b/app/views/order.py
index b424692..1d011b2 100644
--- a/app/views/order.py
+++ b/app/views/order.py
@@ -1,18 +1,13 @@
 import random
+import typing
 from datetime import datetime
 
+import werkzeug
 # from flask import current_app as app
-from flask import (
-    Blueprint,
-    abort,
-    flash,
-    redirect,
-    render_template,
-    request,
-    session,
-    url_for,
-)
+from flask import (Blueprint, abort, flash, redirect, render_template, request,
+                   session, url_for, wrappers)
 from flask_login import current_user, login_required
+from werkzeug.wrappers import Response
 
 from forms import AnonOrderItemForm, OrderForm, OrderItemForm
 from models import Order, OrderItem, User, db
@@ -22,7 +17,7 @@
 
 
 @order_bp.route("/")
-def orders(form=None):
+def orders(form: OrderForm = None) -> str:
     if form is None and not current_user.is_anonymous():
         form = OrderForm()
         location_id = request.args.get("location_id")
@@ -34,7 +29,7 @@ def orders(form=None):
 
 @order_bp.route("/create", methods=["POST"])
 @login_required
-def order_create():
+def order_create() -> typing.Union[str, Response]:
     orderForm = OrderForm()
     orderForm.populate()
     if orderForm.validate_on_submit():
@@ -48,7 +43,7 @@ def order_create():
 
 
 @order_bp.route("/<id>")
-def order(id, form=None):
+def order(id: int, form: OrderForm = None) -> str:
     order = Order.query.filter(Order.id == id).first()
     if order is None:
         abort(404)
@@ -68,7 +63,7 @@ def order(id, form=None):
 
 
 @order_bp.route("/<id>/items")
-def items_showcase(id, form=None):
+def items_showcase(id: int, form: OrderForm = None) -> str:
     order = Order.query.filter(Order.id == id).first()
     if order is None:
         abort(404)
@@ -80,7 +75,7 @@ def items_showcase(id, form=None):
 
 @order_bp.route("/<id>/edit", methods=["GET", "POST"])
 @login_required
-def order_edit(id):
+def order_edit(id: int) -> typing.Union[str, Response]:
     order = Order.query.filter(Order.id == id).first()
     if current_user.id is not order.courrier_id and not current_user.is_admin():
         abort(401)
@@ -96,7 +91,9 @@ def order_edit(id):
 
 
 @order_bp.route("/<id>/create", methods=["POST"])
-def order_item_create(id):
+def order_item_create(id: int) -> typing.Any:
+    # type is 'typing.Union[str, Response]', but this errors due to
+    #   https://github.com/python/mypy/issues/7187
     current_order = Order.query.filter(Order.id == id).first()
     if current_order is None:
         abort(404)
@@ -124,7 +121,7 @@ def order_item_create(id):
 
 @order_bp.route("/<order_id>/<item_id>/paid")
 @login_required
-def item_paid(order_id, item_id):
+def item_paid(order_id: int, item_id: int) -> typing.Optional[Response]:
     item = OrderItem.query.filter(OrderItem.id == item_id).first()
     id = current_user.id
     if item.order.courrier_id == id or current_user.admin:
@@ -137,9 +134,9 @@ def item_paid(order_id, item_id):
 
 @order_bp.route("/<order_id>/<user_name>/user_paid")
 @login_required
-def items_user_paid(order_id, user_name):
+def items_user_paid(order_id: int, user_name: str) -> typing.Optional[Response]:
     user = User.query.filter(User.username == user_name).first()
-    items = []
+    items: typing.List[OrderItem] = []
     if user:
         items = OrderItem.query.filter(
             (OrderItem.user_id == user.id) & (OrderItem.order_id == order_id)
@@ -155,13 +152,15 @@ def items_user_paid(order_id, user_name):
         for item in items:
             item.paid = True
         db.session.commit()
-        flash("Paid %d items for %s" % (items.count(), item.get_name()), "success")
+        flash("Paid %d items for %s" % (len(items), item.get_name()), "success")
         return redirect(url_for("order_bp.order", id=order_id))
     abort(404)
 
 
 @order_bp.route("/<order_id>/<item_id>/delete")
-def delete_item(order_id, item_id):
+def delete_item(order_id: int, item_id: int) -> typing.Any:
+    # type is 'typing.Optional[Response]', but this errors due to
+    #   https://github.com/python/mypy/issues/7187
     item = OrderItem.query.filter(OrderItem.id == item_id).first()
     id = None
     if not current_user.is_anonymous():
@@ -178,7 +177,7 @@ def delete_item(order_id, item_id):
 
 @order_bp.route("/<id>/volunteer")
 @login_required
-def volunteer(id):
+def volunteer(id: int) -> Response:
     order = Order.query.filter(Order.id == id).first()
     if order is None:
         abort(404)
@@ -193,7 +192,7 @@ def volunteer(id):
 
 @order_bp.route("/<id>/close")
 @login_required
-def close_order(id):
+def close_order(id: int) -> typing.Optional[Response]:
     order = Order.query.filter(Order.id == id).first()
     if order is None:
         abort(404)
@@ -208,9 +207,13 @@ def close_order(id):
                 order.courrier_id = courrier.id
         db.session.commit()
         return redirect(url_for("order_bp.order", id=id))
+    # The line below is to make sure mypy doesn't say
+    #   "Missing return statement"
+    #   https://github.com/python/mypy/issues/4223
+    return None
 
 
-def select_user(items):
+def select_user(items) -> typing.Optional[User]:
     user = None
     # remove non users
     items = [i for i in items if i.user_id]
@@ -228,8 +231,8 @@ def select_user(items):
     return user
 
 
-def get_orders(expression=None):
-    orders = []
+def get_orders(expression=None) -> typing.List[Order]:
+    orders: typing.List[OrderForm] = []
     if expression is None:
         expression = (datetime.now() > Order.starttime) & (
             Order.stoptime > datetime.now()
diff --git a/app/views/stats.py b/app/views/stats.py
index 31a1dde..73ad1b1 100644
--- a/app/views/stats.py
+++ b/app/views/stats.py
@@ -8,7 +8,7 @@
 
 
 @stats_blueprint.route("/")
-def stats():
+def stats() -> str:
     data = {
         "amount": {
             "orders": FatOrder.amount(),
diff --git a/app/zeus.py b/app/zeus.py
index b56f70a..8ca77d1 100644
--- a/app/zeus.py
+++ b/app/zeus.py
@@ -1,6 +1,10 @@
-from flask import current_app, flash, redirect, request, session, url_for, Blueprint
+import typing
+
+from flask import (Blueprint, current_app, flash, redirect, request, session,
+                   url_for)
 from flask_login import login_user
-from flask_oauthlib.client import OAuthException, OAuth
+from flask_oauthlib.client import OAuth, OAuthException
+from werkzeug.wrappers import Response
 
 from models import User, db
 
@@ -14,7 +18,9 @@ def zeus_login():
 
 
 @oauth_bp.route("/login/zeus/authorized")
-def authorized():
+def authorized() -> typing.Any:
+    # type is 'typing.Union[str, Response]', but this errors due to
+    #   https://github.com/python/mypy/issues/7187
     resp = current_app.zeus.authorized_response()
     if resp is None:
         return "Access denied: reason=%s error=%s" % (
@@ -60,12 +66,12 @@ def get_zeus_oauth_token():
     return zeus
 
 
-def login_and_redirect_user(user):
+def login_and_redirect_user(user) -> Response:
     login_user(user)
     return redirect(url_for("general_bp.home"))
 
 
-def create_user(username):
+def create_user(username) -> User:
     user = User()
     user.configure(username, False, 1)
     db.session.add(user)
diff --git a/tests.md b/tests.md
new file mode 100644
index 0000000..9f9f54a
--- /dev/null
+++ b/tests.md
@@ -0,0 +1,4 @@
+# Tests
+For this application we run a number of tests, at the moment the tests are:
+- [mypy](http://mypy-lang.org/), type-checking, which you can run using `mypy` with the argument `--ignore-missing-imports` if it says modules cannot be found
+