Expand JWT auth integration tests from 17 to 33 cases

Add comprehensive edge-case coverage for issue #1624:

- Admin delete user endpoint (5 tests): successful delete, self-delete
  prevention, nonexistent user 404, non-admin 403, missing token rejection
- Admin role change gaps (2 tests): nonexistent user 404, non-admin 403
- Input validation (3 tests): invalid email 422, short password 422,
  missing fields 422 for both register and login
- Token edge cases (4 tests): malformed token, wrong-secret token,
  deleted user token, deleted user refresh
- Token claim verification (1 test): login tokens contain correct claims

All tests use mocked DB fixtures and require no live database.

Closes leeworks-agents/SPARC#1624

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/test_auth.py

@@ -1,13 +1,29 @@
-"""Tests for JWT authentication flow: register, login, protected routes, refresh, admin access."""
+"""Tests for JWT authentication flow: register, login, protected routes, refresh, admin access.
 
-from datetime import datetime, timezone
+Covers all five scenarios required by issue #1624:
+1. Registration (POST /auth/register)
+2. Login (POST /auth/login)
+3. Protected route access (GET /auth/me) -- valid, missing, expired, wrong-type tokens
+4. Token refresh (POST /auth/refresh)
+5. Admin-only endpoints (GET /admin/users, PATCH role, DELETE user)
+
+All tests use mocked DB fixtures and require no live database.
+"""
+
+from datetime import datetime, timedelta, timezone
 from unittest.mock import MagicMock, patch
 
+import jwt as pyjwt
 import pytest
 from fastapi.testclient import TestClient
 
 from SPARC.api import app
-from SPARC.auth import create_access_token, create_refresh_token
+from SPARC.auth import (
+    JWT_ALGORITHM,
+    JWT_SECRET,
+    create_access_token,
+    create_refresh_token,
+)
 
 
 @pytest.fixture
@@ -171,13 +187,6 @@ class TestGetMe:
 
     def test_expired_token_returns_401(self, client, mock_db):
         """An expired token should return 401."""
-        # Create a token that has already expired
-        from datetime import timedelta
-
-        import jwt as pyjwt
-
-        from SPARC.auth import JWT_ALGORITHM, JWT_SECRET
-
         payload = {
             "sub": "1",
             "email": "user@test.com",
@@ -301,3 +310,193 @@ class TestAdminUsers:
 
         assert response.status_code == 400
         assert "own role" in response.json()["detail"].lower()
+
+    def test_role_change_nonexistent_user_returns_404(self, client, mock_db):
+        """Changing role for a user that does not exist should return 404."""
+        admin = _make_admin_user()
+        mock_db.get_user_by_id.return_value = admin
+        mock_db.update_user_role.return_value = None
+
+        response = client.patch(
+            "/admin/users/999/role",
+            json={"role": "admin"},
+            headers=_auth_header(admin),
+        )
+
+        assert response.status_code == 404
+        assert "not found" in response.json()["detail"].lower()
+
+    def test_regular_user_cannot_change_role(self, client, mock_db):
+        """Non-admin user should receive 403 when trying to change roles."""
+        user = _make_regular_user()
+        mock_db.get_user_by_id.return_value = user
+
+        response = client.patch(
+            "/admin/users/1/role",
+            json={"role": "admin"},
+            headers=_auth_header(user),
+        )
+
+        assert response.status_code == 403
+
+
+class TestAdminDeleteUser:
+    """DELETE /admin/users/{user_id}"""
+
+    def test_admin_can_delete_user(self, client, mock_db):
+        """Admin should be able to delete another user."""
+        admin = _make_admin_user()
+        mock_db.get_user_by_id.return_value = admin
+        mock_db.delete_user.return_value = True
+
+        response = client.delete(
+            "/admin/users/2",
+            headers=_auth_header(admin),
+        )
+
+        assert response.status_code == 200
+        assert "deleted" in response.json()["message"].lower()
+        mock_db.delete_user.assert_called_once_with(2)
+
+    def test_admin_cannot_delete_self(self, client, mock_db):
+        """Admin should not be able to delete themselves."""
+        admin = _make_admin_user()
+        mock_db.get_user_by_id.return_value = admin
+
+        response = client.delete(
+            "/admin/users/1",
+            headers=_auth_header(admin),
+        )
+
+        assert response.status_code == 400
+        assert "yourself" in response.json()["detail"].lower()
+
+    def test_delete_nonexistent_user_returns_404(self, client, mock_db):
+        """Deleting a user that does not exist should return 404."""
+        admin = _make_admin_user()
+        mock_db.get_user_by_id.return_value = admin
+        mock_db.delete_user.return_value = False
+
+        response = client.delete(
+            "/admin/users/999",
+            headers=_auth_header(admin),
+        )
+
+        assert response.status_code == 404
+        assert "not found" in response.json()["detail"].lower()
+
+    def test_regular_user_cannot_delete_user(self, client, mock_db):
+        """Non-admin user should receive 403 when trying to delete users."""
+        user = _make_regular_user()
+        mock_db.get_user_by_id.return_value = user
+
+        response = client.delete(
+            "/admin/users/1",
+            headers=_auth_header(user),
+        )
+
+        assert response.status_code == 403
+
+    def test_no_token_cannot_delete_user(self, client):
+        """Missing token should be rejected for delete endpoint."""
+        response = client.delete("/admin/users/1")
+        assert response.status_code in (401, 403)
+
+
+class TestEdgeCases:
+    """Additional edge-case tests for auth robustness."""
+
+    def test_register_invalid_email_returns_422(self, client, mock_db):
+        """Registration with an invalid email format should return 422."""
+        response = client.post(
+            "/auth/register",
+            json={"email": "not-an-email", "password": "securepass123"},
+        )
+
+        assert response.status_code == 422
+
+    def test_register_short_password_returns_422(self, client, mock_db):
+        """Registration with a password shorter than 8 chars should return 422."""
+        response = client.post(
+            "/auth/register",
+            json={"email": "user@test.com", "password": "short"},
+        )
+
+        assert response.status_code == 422
+
+    def test_register_missing_fields_returns_422(self, client, mock_db):
+        """Registration with missing fields should return 422."""
+        response = client.post("/auth/register", json={})
+        assert response.status_code == 422
+
+    def test_login_missing_fields_returns_422(self, client, mock_db):
+        """Login with missing fields should return 422."""
+        response = client.post("/auth/login", json={"email": "user@test.com"})
+        assert response.status_code == 422
+
+    def test_malformed_token_returns_401(self, client, mock_db):
+        """A completely malformed token string should return 401."""
+        response = client.get(
+            "/auth/me",
+            headers={"Authorization": "Bearer not.a.valid.jwt.token"},
+        )
+        assert response.status_code == 401
+
+    def test_token_with_wrong_secret_returns_401(self, client, mock_db):
+        """A token signed with a different secret should return 401."""
+        payload = {
+            "sub": "1",
+            "email": "user@test.com",
+            "role": "user",
+            "exp": datetime.now(timezone.utc) + timedelta(hours=1),
+            "type": "access",
+        }
+        wrong_secret_token = pyjwt.encode(payload, "wrong-secret", algorithm=JWT_ALGORITHM)
+
+        response = client.get(
+            "/auth/me",
+            headers={"Authorization": f"Bearer {wrong_secret_token}"},
+        )
+        assert response.status_code == 401
+
+    def test_token_for_deleted_user_returns_401(self, client, mock_db):
+        """A valid token for a user no longer in the DB should return 401."""
+        user = _make_regular_user()
+        mock_db.get_user_by_id.return_value = None  # user was deleted
+
+        response = client.get("/auth/me", headers=_auth_header(user))
+        assert response.status_code == 401
+
+    def test_refresh_for_deleted_user_returns_401(self, client, mock_db):
+        """Refreshing a token for a deleted user should return 401."""
+        user = _make_regular_user()
+        mock_db.get_user_by_id.return_value = None
+        refresh = create_refresh_token(user["id"], user["email"], user["role"])
+
+        response = client.post(
+            "/auth/refresh", json={"refresh_token": refresh}
+        )
+        assert response.status_code == 401
+
+    def test_login_returns_decodable_tokens(self, client, mock_db):
+        """Tokens returned by login should be decodable and contain expected claims."""
+        user = _make_regular_user()
+        mock_db.authenticate_user.return_value = user
+
+        response = client.post(
+            "/auth/login",
+            json={"email": "user@test.com", "password": "correctpassword"},
+        )
+
+        data = response.json()
+        access_payload = pyjwt.decode(
+            data["access_token"], JWT_SECRET, algorithms=[JWT_ALGORITHM]
+        )
+        assert access_payload["sub"] == str(user["id"])
+        assert access_payload["email"] == user["email"]
+        assert access_payload["type"] == "access"
+
+        refresh_payload = pyjwt.decode(
+            data["refresh_token"], JWT_SECRET, algorithms=[JWT_ALGORITHM]
+        )
+        assert refresh_payload["type"] == "refresh"