diff --git a/7project/backend/tests/test_e2e_auth_flow.py b/7project/backend/tests/test_e2e.py
similarity index 51%
rename from 7project/backend/tests/test_e2e_auth_flow.py
rename to 7project/backend/tests/test_e2e.py
index 7ad18d2..49a57e3 100644
--- a/7project/backend/tests/test_e2e_auth_flow.py
+++ b/7project/backend/tests/test_e2e.py
@@ -4,7 +4,7 @@ from httpx import AsyncClient, ASGITransport
 from fastapi import status
 
 
-def test_e2e_minimal_auth_flow(client):
+def test_e2e(client):
     # 1) Service is alive
     alive = client.get("/")
     assert alive.status_code == status.HTTP_200_OK
@@ -95,4 +95,85 @@ async def test_e2e_transaction_workflow(fastapi_app, test_user):
 
         # NEW STEP: Clean up the created category
         delete_category_resp = await ac.delete(f"/categories/{category_id}", headers=headers)
-        assert delete_category_resp.status_code in (status.HTTP_200_OK, status.HTTP_204_NO_CONTENT)
\ No newline at end of file
+        assert delete_category_resp.status_code in (status.HTTP_200_OK, status.HTTP_204_NO_CONTENT)
+
+@pytest.mark.asyncio
+async def test_register_then_login_and_fetch_me(fastapi_app):
+    transport = ASGITransport(app=fastapi_app, raise_app_exceptions=True)
+    async with AsyncClient(transport=transport, base_url="http://testserver") as ac:
+        email = "newuser@example.com"
+        password = "StrongPassw0rd!"
+        reg = await ac.post("/auth/register", json={"email": email, "password": password})
+        assert reg.status_code in (status.HTTP_201_CREATED, status.HTTP_200_OK)
+
+        login = await ac.post("/auth/jwt/login", data={"username": email, "password": password})
+        assert login.status_code == status.HTTP_200_OK
+        token = login.json()["access_token"]
+        me = await ac.get("/users/me", headers={"Authorization": f"Bearer {token}"})
+        assert me.status_code == status.HTTP_200_OK
+        assert me.json()["email"] == email
+
+
+@pytest.mark.asyncio
+async def test_delete_current_user_revokes_access(fastapi_app):
+    transport = ASGITransport(app=fastapi_app, raise_app_exceptions=True)
+    async with AsyncClient(transport=transport, base_url="http://testserver") as ac:
+        email = "todelete@example.com"
+        password = "Passw0rd!"
+        reg = await ac.post("/auth/register", json={"email": email, "password": password})
+        assert reg.status_code in (status.HTTP_200_OK, status.HTTP_201_CREATED)
+
+        login = await ac.post("/auth/jwt/login", data={"username": email, "password": password})
+        token = login.json()["access_token"]
+        headers = {"Authorization": f"Bearer {token}"}
+
+        # Delete self
+        d = await ac.delete("/users/me", headers=headers)
+        assert d.status_code == status.HTTP_204_NO_CONTENT
+
+        # Access should now fail
+        me = await ac.get("/users/me", headers=headers)
+        assert me.status_code in (status.HTTP_401_UNAUTHORIZED, status.HTTP_403_FORBIDDEN)
+
+
+@pytest.mark.asyncio
+async def test_update_category_conflict_and_404(fastapi_app, test_user):
+    transport = ASGITransport(app=fastapi_app)
+    async with AsyncClient(transport=transport, base_url="http://testserver") as ac:
+        token = (await ac.post("/auth/jwt/login", data=test_user)).json()["access_token"]
+        h = {"Authorization": f"Bearer {token}"}
+
+        a = (await ac.post("/categories/create", json={"name": "A"}, headers=h)).json()
+        b = (await ac.post("/categories/create", json={"name": "B"}, headers=h)).json()
+
+        # Attempt to rename A -> B should conflict
+        conflict = await ac.patch(f"/categories/{a['id']}", json={"name": "B"}, headers=h)
+        assert conflict.status_code == status.HTTP_409_CONFLICT
+
+        # Update non-existent
+        missing = await ac.patch("/categories/999999", json={"name": "Z"}, headers=h)
+        assert missing.status_code == status.HTTP_404_NOT_FOUND
+
+@pytest.mark.asyncio
+async def test_category_cross_user_isolation(fastapi_app):
+    transport = ASGITransport(app=fastapi_app)
+    async with AsyncClient(transport=transport, base_url="http://testserver") as ac:
+        # user1
+        u1 = {"email": "u1@example.com", "password": "Aaaaaa1!"}
+        assert (await ac.post("/auth/register", json=u1)).status_code in (200, 201)
+        t1 = (await ac.post("/auth/jwt/login", data={"username": u1["email"], "password": u1["password"]})).json()["access_token"]
+
+        # user1 creates a category
+        c = (await ac.post("/categories/create", json={"name": "Private"}, headers={"Authorization": f"Bearer {t1}"})).json()
+
+        # user2
+        u2 = {"email": "u2@example.com", "password": "Aaaaaa1!"}
+        assert (await ac.post("/auth/register", json=u2)).status_code in (200, 201)
+        t2 = (await ac.post("/auth/jwt/login", data={"username": u2["email"], "password": u2["password"]})).json()["access_token"]
+
+        # user2 cannot read/delete user1's category
+        g = await ac.get(f"/categories/{c['id']}", headers={"Authorization": f"Bearer {t2}"})
+        assert g.status_code == status.HTTP_404_NOT_FOUND
+        d = await ac.delete(f"/categories/{c['id']}", headers={"Authorization": f"Bearer {t2}"})
+        assert d.status_code == status.HTTP_404_NOT_FOUND
+
diff --git a/7project/backend/tests/test_integration_app.py b/7project/backend/tests/test_integration_app.py
index c924e25..5806452 100644
--- a/7project/backend/tests/test_integration_app.py
+++ b/7project/backend/tests/test_integration_app.py
@@ -63,4 +63,108 @@ async def test_create_transaction_missing_amount_fails(fastapi_app, test_user):
         resp = await ac.post("/transactions/create", json=invalid_payload, headers=headers)
 
         # 4. Assert the expected validation error
-        assert resp.status_code == status.HTTP_422_UNPROCESSABLE_ENTITY
+        assert resp.status_code == status.HTTP_422_UNPROCESSABLE_CONTENT
+
+
+@pytest.mark.asyncio
+async def test_login_invalid_credentials(fastapi_app, test_user):
+    transport = ASGITransport(app=fastapi_app)
+    async with AsyncClient(transport=transport, base_url="http://testserver") as ac:
+        bad = await ac.post("/auth/jwt/login", data={"username": test_user["username"], "password": "nope"})
+        assert bad.status_code in (status.HTTP_401_UNAUTHORIZED, status.HTTP_400_BAD_REQUEST)
+        unknown = await ac.post("/auth/jwt/login", data={"username": "nouser@example.com", "password": "x"})
+        assert unknown.status_code in (status.HTTP_401_UNAUTHORIZED, status.HTTP_400_BAD_REQUEST)
+
+
+@pytest.mark.asyncio
+async def test_category_duplicate_name_conflict(fastapi_app, test_user):
+    transport = ASGITransport(app=fastapi_app)
+    async with AsyncClient(transport=transport, base_url="http://testserver") as ac:
+        token = (await ac.post("/auth/jwt/login", data=test_user)).json()["access_token"]
+        h = {"Authorization": f"Bearer {token}"}
+
+        p = {"name": "Food"}
+        r1 = await ac.post("/categories/create", json=p, headers=h)
+        assert r1.status_code == status.HTTP_201_CREATED
+        r2 = await ac.post("/categories/create", json=p, headers=h)
+        assert r2.status_code == status.HTTP_409_CONFLICT
+
+@pytest.mark.asyncio
+async def test_create_transaction_invalid_date_format(fastapi_app, test_user):
+    transport = ASGITransport(app=fastapi_app)
+    async with AsyncClient(transport=transport, base_url="http://testserver") as ac:
+        token = (await ac.post("/auth/jwt/login", data=test_user)).json()["access_token"]
+        h = {"Authorization": f"Bearer {token}"}
+        bad = await ac.post("/transactions/create", json={"amount": 10, "description": "x", "date": "31-12-2024"}, headers=h)
+        assert bad.status_code == status.HTTP_400_BAD_REQUEST
+
+@pytest.mark.asyncio
+async def test_update_transaction_rejects_duplicate_category_ids(fastapi_app, test_user):
+    transport = ASGITransport(app=fastapi_app)
+    async with AsyncClient(transport=transport, base_url="http://testserver") as ac:
+        token = (await ac.post("/auth/jwt/login", data=test_user)).json()["access_token"]
+        h = {"Authorization": f"Bearer {token}"}
+        tx = (await ac.post("/transactions/create", json={"amount": 5, "description": "x"}, headers=h)).json()
+        dup = await ac.patch(f"/transactions/{tx['id']}/edit", json={"category_ids": [1, 1]}, headers=h)
+        assert dup.status_code == status.HTTP_400_BAD_REQUEST
+
+@pytest.mark.asyncio
+async def test_assign_unassign_category_not_found_cases(fastapi_app, test_user):
+    transport = ASGITransport(app=fastapi_app)
+    async with AsyncClient(transport=transport, base_url="http://testserver") as ac:
+        token = (await ac.post("/auth/jwt/login", data=test_user)).json()["access_token"]
+        h = {"Authorization": f"Bearer {token}"}
+
+        # Create tx and category
+        tx = (await ac.post("/transactions/create", json={"amount": 1, "description": "a"}, headers=h)).json()
+        cat = (await ac.post("/categories/create", json={"name": "X"}, headers=h)).json()
+
+        # Missing transaction
+        r1 = await ac.post(f"/transactions/999999/categories/{cat['id']}", headers=h)
+        assert r1.status_code == status.HTTP_404_NOT_FOUND
+
+        # Missing category
+        r2 = await ac.post(f"/transactions/{tx['id']}/categories/999999", headers=h)
+        assert r2.status_code == status.HTTP_404_NOT_FOUND
+
+@pytest.mark.asyncio
+async def test_transactions_date_filter_and_balance_series(fastapi_app, test_user):
+    transport = ASGITransport(app=fastapi_app)
+    async with AsyncClient(transport=transport, base_url="http://testserver") as ac:
+        token = (await ac.post("/auth/jwt/login", data=test_user)).json()["access_token"]
+        h = {"Authorization": f"Bearer {token}"}
+
+        # Seed transactions spanning days
+        data = [
+            {"amount": 100, "description": "day1", "date": "2024-01-01"},
+            {"amount": -25, "description": "day2", "date": "2024-01-02"},
+            {"amount": 50, "description": "day3", "date": "2024-01-03"},
+        ]
+        for p in data:
+            r = await ac.post("/transactions/create", json=p, headers=h)
+            assert r.status_code == status.HTTP_201_CREATED
+
+        # Filtered list (2nd and 3rd only)
+        lst = await ac.get("/transactions/", params={"start_date": "2024-01-02", "end_date": "2024-01-03"}, headers=h)
+        assert lst.status_code == status.HTTP_200_OK
+        assert len(lst.json()) == 2
+
+        # Balance series should be cumulative per date
+        series = await ac.get("/transactions/balance_series", headers=h)
+        assert series.status_code == status.HTTP_200_OK
+        s = series.json()
+        assert s == [
+            {"date": "2024-01-01", "balance": 100.0},
+            {"date": "2024-01-02", "balance": 75.0},
+            {"date": "2024-01-03", "balance": 125.0},
+        ]
+
+@pytest.mark.asyncio
+async def test_delete_transaction_not_found(fastapi_app, test_user):
+    transport = ASGITransport(app=fastapi_app)
+    async with AsyncClient(transport=transport, base_url="http://testserver") as ac:
+        token = (await ac.post("/auth/jwt/login", data=test_user)).json()["access_token"]
+        h = {"Authorization": f"Bearer {token}"}
+        r = await ac.delete("/transactions/999999/delete", headers=h)
+        assert r.status_code == status.HTTP_404_NOT_FOUND
+