diff --git a/.vscode/settings.json b/.vscode/settings.json
index 8c125bf..7d9bb57 100644
--- a/.vscode/settings.json
+++ b/.vscode/settings.json
@@ -2,5 +2,10 @@
     "cSpell.language": "en,de-DE",
     "cSpell.words": [
         "Chiara"
-    ]
+    ],
+    "python.testing.pytestArgs": [
+        "backend"
+    ],
+    "python.testing.unittestEnabled": false,
+    "python.testing.pytestEnabled": true
 }
\ No newline at end of file
diff --git a/backend/dev.db b/backend/dev.db
deleted file mode 100644
index 5cfe680..0000000
Binary files a/backend/dev.db and /dev/null differ
diff --git a/backend/src/backend/__pycache__/main.cpython-314.pyc b/backend/src/backend/__pycache__/main.cpython-314.pyc
index 221f8aa..1f02bd3 100644
Binary files a/backend/src/backend/__pycache__/main.cpython-314.pyc and b/backend/src/backend/__pycache__/main.cpython-314.pyc differ
diff --git a/backend/src/backend/internal/__pycache__/__init__.cpython-314.pyc b/backend/src/backend/internal/__pycache__/__init__.cpython-314.pyc
index 16a96f9..e8e4a82 100644
Binary files a/backend/src/backend/internal/__pycache__/__init__.cpython-314.pyc and b/backend/src/backend/internal/__pycache__/__init__.cpython-314.pyc differ
diff --git a/backend/src/backend/internal/__pycache__/database.cpython-314.pyc b/backend/src/backend/internal/__pycache__/database.cpython-314.pyc
index ab0bf1b..b6681d4 100644
Binary files a/backend/src/backend/internal/__pycache__/database.cpython-314.pyc and b/backend/src/backend/internal/__pycache__/database.cpython-314.pyc differ
diff --git a/backend/src/backend/internal/database.py b/backend/src/backend/internal/database.py
index 16820d8..de12497 100644
--- a/backend/src/backend/internal/database.py
+++ b/backend/src/backend/internal/database.py
@@ -2,6 +2,7 @@ from collections.abc import Generator
 from sqlmodel import Session
 from sqlmodel import SQLModel
 from sqlmodel import create_engine
+
 sqlite_file = "dev.db"
 sqlite_url = f"sqlite:///{sqlite_file}"
 
@@ -13,4 +14,4 @@ def create_db_and_tables():
 
 def get_session() -> Generator[Session, None, None]:
     with Session(engine) as session:
-        yield session
+        yield session
\ No newline at end of file
diff --git a/backend/src/backend/main.py b/backend/src/backend/main.py
index 8095601..e9892ce 100644
--- a/backend/src/backend/main.py
+++ b/backend/src/backend/main.py
@@ -1,4 +1,5 @@
-from .routers import users
+from sqlmodel import SQLModel
+from .routers import users, comments
 from backend.internal.database import create_db_and_tables
 from fastapi import APIRouter
 from fastapi import FastAPI
@@ -16,3 +17,6 @@ def on_startup():
 router = APIRouter()
 
 app.include_router(users.router)
+app.include_router(comments.router)
+
+print(SQLModel.metadata.tables.keys())
diff --git a/backend/src/backend/models/__init__.py b/backend/src/backend/models/__init__.py
index e69de29..c27d1df 100644
--- a/backend/src/backend/models/__init__.py
+++ b/backend/src/backend/models/__init__.py
@@ -0,0 +1,2 @@
+from .user import User
+from .comment import Comment
\ No newline at end of file
diff --git a/backend/src/backend/models/__pycache__/__init__.cpython-314.pyc b/backend/src/backend/models/__pycache__/__init__.cpython-314.pyc
index eaefbcb..63e9ebf 100644
Binary files a/backend/src/backend/models/__pycache__/__init__.cpython-314.pyc and b/backend/src/backend/models/__pycache__/__init__.cpython-314.pyc differ
diff --git a/backend/src/backend/models/__pycache__/comment.cpython-314.pyc b/backend/src/backend/models/__pycache__/comment.cpython-314.pyc
index 3611c7f..e3d9eaa 100644
Binary files a/backend/src/backend/models/__pycache__/comment.cpython-314.pyc and b/backend/src/backend/models/__pycache__/comment.cpython-314.pyc differ
diff --git a/backend/src/backend/models/__pycache__/user.cpython-314.pyc b/backend/src/backend/models/__pycache__/user.cpython-314.pyc
index ce1b3d8..69ea8e6 100644
Binary files a/backend/src/backend/models/__pycache__/user.cpython-314.pyc and b/backend/src/backend/models/__pycache__/user.cpython-314.pyc differ
diff --git a/backend/src/backend/models/comment.py b/backend/src/backend/models/comment.py
index 9d15f97..e1fb5dc 100644
--- a/backend/src/backend/models/comment.py
+++ b/backend/src/backend/models/comment.py
@@ -1,12 +1,12 @@
+from datetime import datetime
 import uuid
-from typing import TYPE_CHECKING, Optional
+from typing import TYPE_CHECKING
 from sqlmodel import Relationship
-from sqlmodel import DateTime
 from sqlmodel import Field
 from sqlmodel import SQLModel
 
 if TYPE_CHECKING:
-    from ..models.user import User
+    from backend.models.user import User
 
 class CommentBase(SQLModel):
     pass
@@ -15,6 +15,6 @@ class Comment(CommentBase, table=True):
     id: uuid.UUID | None = Field(default_factory=uuid.uuid4, primary_key=True)
     slug: str = Field(index=True)
     content: str = Field()
-    date_time: DateTime = Field(default=DateTime())
+    date_time: datetime = Field(default=datetime.now())
     user_id: uuid.UUID = Field(foreign_key="user.id")
-    user: Optional["User"] = Relationship(back_populates="comments")
\ No newline at end of file
+    user: "User" = Relationship(back_populates="comments")
\ No newline at end of file
diff --git a/backend/src/backend/models/user.py b/backend/src/backend/models/user.py
index 3937665..90923aa 100644
--- a/backend/src/backend/models/user.py
+++ b/backend/src/backend/models/user.py
@@ -5,20 +5,20 @@ from sqlmodel import Relationship
 from sqlmodel import SQLModel
 
 if TYPE_CHECKING:
-    from ..models.comment import Comment
+    from backend.models.comment import Comment
 
 class UserBase(SQLModel):
     pass
 
-class User(UserBase):
-    id: uuid.UUID | None = Field(default_factory=uuid.uuid4, primary_key=True)
+class User(UserBase, table=True):
+    id: uuid.UUID = Field(default_factory=uuid.uuid4, primary_key=True)
     email: str = Field(unique=True)
     name: str = Field(unique=True)
-    user_code: str = Field(unique=True) # TODO: create generation function
+    user_code: str = Field(default="1234",unique=True) # TODO: create Generator
     subscription: bool = Field()
     comments: list["Comment"] = Relationship(back_populates="user")
 
-class RegisterUser(UserBase):
+class NewUser(UserBase):
     email: str
     name: str
     subscription: bool
diff --git a/backend/src/backend/routers/__pycache__/comments.cpython-314.pyc b/backend/src/backend/routers/__pycache__/comments.cpython-314.pyc
new file mode 100644
index 0000000..6619cab
Binary files /dev/null and b/backend/src/backend/routers/__pycache__/comments.cpython-314.pyc differ
diff --git a/backend/src/backend/routers/__pycache__/test_users.cpython-314-pytest-9.1.1.pyc b/backend/src/backend/routers/__pycache__/test_users.cpython-314-pytest-9.1.1.pyc
index ee1f03b..a17eab1 100644
Binary files a/backend/src/backend/routers/__pycache__/test_users.cpython-314-pytest-9.1.1.pyc and b/backend/src/backend/routers/__pycache__/test_users.cpython-314-pytest-9.1.1.pyc differ
diff --git a/backend/src/backend/routers/__pycache__/users.cpython-314.pyc b/backend/src/backend/routers/__pycache__/users.cpython-314.pyc
index 2c4f339..d95f89b 100644
Binary files a/backend/src/backend/routers/__pycache__/users.cpython-314.pyc and b/backend/src/backend/routers/__pycache__/users.cpython-314.pyc differ
diff --git a/backend/src/backend/routers/comments.py b/backend/src/backend/routers/comments.py
index 83ab410..6393035 100644
--- a/backend/src/backend/routers/comments.py
+++ b/backend/src/backend/routers/comments.py
@@ -1,4 +1,24 @@
 
 # add comment
 # delete comment
-# get comments
\ No newline at end of file
+# get comments
+
+from backend.internal.database import get_session
+from fastapi import Depends
+from sqlmodel import Session
+from fastapi import APIRouter
+from ..models.comment import Comment 
+
+router = APIRouter(
+    prefix="/comments",
+    tags=["comments"],
+    dependencies=[],
+    responses={404: {"description": "Not found"}},
+)
+
+@router.post("/")
+def register_user(session: Session = Depends(get_session)):
+    comment = {"test":"test"}
+    comment1 = Comment.model_validate(comment)
+    session.add(comment)
+    session.commit()
diff --git a/backend/src/backend/routers/test_users.py b/backend/src/backend/routers/test_users.py
index cdf58db..ff62a1c 100644
--- a/backend/src/backend/routers/test_users.py
+++ b/backend/src/backend/routers/test_users.py
@@ -1,15 +1,57 @@
-from httpx2 import post
-from backend.models.user import RegisterUser
+from backend.models.user import User
+from backend.internal.database import get_session
+from sqlmodel import Session
+from sqlmodel import StaticPool
+from sqlmodel import create_engine
+import pytest
+from backend.internal.database import engine
+from sqlmodel import SQLModel
 from backend.main import app
 from fastapi.testclient import TestClient
 
-client = TestClient(app)
+@pytest.fixture(name="session")
+def session_fixture():
+    engine = create_engine(
+        "sqlite://", connect_args={"check_same_thread": False}, poolclass=StaticPool
+    )
+    SQLModel.metadata.create_all(engine)
+    with Session(engine) as session:
+        yield session
 
-def test_register_user_works():
+
+@pytest.fixture(name="client")  
+def client_fixture(session: Session):  
+    def get_session_override():  
+        return session
+
+    app.dependency_overrides[get_session] = get_session_override  
+
+    client = TestClient(app)  
+    yield client  
+    app.dependency_overrides.clear()  
+
+
+
+
+def test_register_user_works(client: TestClient):
+    print(SQLModel.metadata.tables.keys())
     new_user = {
-        "email": "Test",
+        "email": "Test@Test.test",
         "name": "Test1",
         "subscription": True
     }
     response = client.post(url="/users/", json=new_user)
-    assert response.status_code == 200
\ No newline at end of file
+    assert response.status_code == 200
+
+def test_email_not_unique(session: Session, client: TestClient):
+    new_user = {
+        "email": "Test@Test.test",
+        "name": "Test1",
+        "subscription": True
+    }
+    user = User.model_validate(new_user)
+    session.add(user)
+    session.commit()
+    response = client.post(url="/users/", json=new_user)
+    
+    assert response.status_code == 400
\ No newline at end of file
diff --git a/backend/src/backend/routers/users.py b/backend/src/backend/routers/users.py
index 3bb20fa..8b8cef1 100644
--- a/backend/src/backend/routers/users.py
+++ b/backend/src/backend/routers/users.py
@@ -8,6 +8,11 @@
 
 # delete all deactivated users after 48h
 
+from starlette.status import HTTP_400_BAD_REQUEST
+from fastapi import HTTPException
+from sqlalchemy.exc import IntegrityError
+from backend.models.user import User
+from backend.models.user import NewUser
 from backend.internal.database import get_session
 from fastapi import Depends
 from sqlmodel import Session
@@ -21,5 +26,12 @@ router = APIRouter(
 )
 
 @router.post("/")
-def register_user(session: Session = Depends(get_session)):
-    pass
+def register_user(new_user: NewUser, session: Session = Depends(get_session)):
+    user = User.model_validate(new_user)
+    
+    try:
+        session.add(user)
+        session.commit()
+    except IntegrityError as e:
+        session.rollback()
+        raise HTTPException(HTTP_400_BAD_REQUEST)