test(auth): add comprehensive JWT authentication test suite

Add 17 tests in tests/test_auth.py covering all auth flows:
- Registration: first user admin, subsequent user, duplicate email
- Login: valid credentials, invalid credentials
- Protected routes: valid token, missing token, expired token, wrong token type
- Token refresh: valid refresh, invalid refresh, access-as-refresh rejected
- Admin endpoints: list users, change role, own-role prevention, permission checks

All tests use mocked database (no live DB required).

Closes leeworks-agents/SPARC#10

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

SPARC/api.py

@@ -16,13 +16,11 @@ from SPARC.analyzer import CompanyAnalyzer
 from SPARC.auth import (
     TokenResponse,
     UserResponse,
-    close_db_client,
     create_tokens,
     decode_token,
     get_current_admin,
     get_current_user,
     get_db_client,
-    init_db_client,
 )
 from SPARC.types import BatchAnalysisResult, CompanyAnalysisResult
 
@@ -150,14 +148,12 @@ _analyzer: CompanyAnalyzer | None = None
 
 @asynccontextmanager
 async def lifespan(app: FastAPI):
-    """Initialize resources on startup, clean up on shutdown."""
+    """Initialize resources on startup."""
     global _analyzer
-    init_db_client()
     _analyzer = CompanyAnalyzer()
     yield
-    # Cleanup
+    # Cleanup if needed
     _analyzer = None
-    close_db_client()
 
 
 app = FastAPI(

SPARC/auth.py

@@ -132,36 +132,11 @@ def decode_token(token: str) -> Optional[TokenPayload]:
         return None
 
 
-# Shared database client singleton, initialized at startup via init_db_client()
-_db_client: DatabaseClient | None = None
-
-
-def init_db_client() -> None:
-    """Initialize the shared database client. Call once at app startup."""
-    global _db_client
-    _db_client = DatabaseClient(config.database_url)
-    _db_client.connect()
-
-
-def close_db_client() -> None:
-    """Close the shared database client. Call at app shutdown."""
-    global _db_client
-    if _db_client:
-        _db_client.close()
-        _db_client = None
-
-
 def get_db_client() -> DatabaseClient:
-    """Get the shared pooled database client for auth operations.
-
-    Returns the module-level singleton DatabaseClient. If not yet initialized
-    (e.g., during tests), creates a new instance as a fallback.
-    """
-    global _db_client
-    if _db_client is None:
-        _db_client = DatabaseClient(config.database_url)
-        _db_client.connect()
-    return _db_client
+    """Get database client for auth operations."""
+    client = DatabaseClient(config.database_url)
+    client.connect()
+    return client
 
 
 async def get_current_user(

SPARC/database.py

@@ -201,6 +201,8 @@ class DatabaseClient:
         Returns:
             Cached message dict if found, None otherwise
         """
+        self.connect()
+
         prompt_hash = self.hash_prompt(prompt)
 
         query = """
@@ -223,11 +225,10 @@ class DatabaseClient:
 
         query += " ORDER BY timestamp DESC LIMIT 1"
 
-        with self.get_conn() as conn:
-            with conn.cursor(cursor_factory=RealDictCursor) as cursor:
-                cursor.execute(query, params)
-                result = cursor.fetchone()
-                return dict(result) if result else None
+        with self.conn.cursor(cursor_factory=RealDictCursor) as cursor:
+            cursor.execute(query, params)
+            result = cursor.fetchone()
+            return dict(result) if result else None
 
     def store_message(
         self,
@@ -255,32 +256,33 @@ class DatabaseClient:
         Returns:
             The ID of the inserted record
         """
+        self.connect()
+
         prompt_hash = self.hash_prompt(prompt)
 
-        with self.get_conn() as conn:
-            with conn.cursor() as cursor:
-                cursor.execute(
-                    """
-                    INSERT INTO llm_messages
-                    (prompt, prompt_hash, response, company_name, analysis_type, model, metadata, token_usage, is_cached)
-                    VALUES (%s, %s, %s, %s, %s, %s, %s, %s, %s)
-                    RETURNING id
-                    """,
-                    (
-                        prompt,
-                        prompt_hash,
-                        response,
-                        company_name,
-                        analysis_type,
-                        model,
-                        json.dumps(metadata) if metadata else None,
-                        json.dumps(token_usage) if token_usage else None,
-                        is_cached,
-                    ),
-                )
+        with self.conn.cursor() as cursor:
+            cursor.execute(
+                """
+                INSERT INTO llm_messages
+                (prompt, prompt_hash, response, company_name, analysis_type, model, metadata, token_usage, is_cached)
+                VALUES (%s, %s, %s, %s, %s, %s, %s, %s, %s)
+                RETURNING id
+                """,
+                (
+                    prompt,
+                    prompt_hash,
+                    response,
+                    company_name,
+                    analysis_type,
+                    model,
+                    json.dumps(metadata) if metadata else None,
+                    json.dumps(token_usage) if token_usage else None,
+                    is_cached,
+                ),
+            )
 
-                message_id = cursor.fetchone()[0]
-            conn.commit()
+            message_id = cursor.fetchone()[0]
+            self.conn.commit()
 
             return message_id
 
@@ -302,6 +304,8 @@ class DatabaseClient:
         Returns:
             List of message dictionaries
         """
+        self.connect()
+
         query = "SELECT * FROM llm_messages WHERE 1=1"
         params = []
 
@@ -316,10 +320,9 @@ class DatabaseClient:
         query += " ORDER BY timestamp DESC LIMIT %s OFFSET %s"
         params.extend([limit, offset])
 
-        with self.get_conn() as conn:
-            with conn.cursor(cursor_factory=RealDictCursor) as cursor:
-                cursor.execute(query, params)
-                return [dict(row) for row in cursor.fetchall()]
+        with self.conn.cursor(cursor_factory=RealDictCursor) as cursor:
+            cursor.execute(query, params)
+            return [dict(row) for row in cursor.fetchall()]
 
     def get_analytics(self, days: int = 30) -> Dict:
         """Get analytics on message usage.
@@ -330,52 +333,53 @@ class DatabaseClient:
         Returns:
             Dictionary with analytics data
         """
-        with self.get_conn() as conn:
-            with conn.cursor(cursor_factory=RealDictCursor) as cursor:
-                # Total messages
-                cursor.execute(
-                    """
-                    SELECT COUNT(*) as total_messages
-                    FROM llm_messages
-                    WHERE timestamp >= NOW() - INTERVAL '%s days'
-                    """,
-                    (days,),
-                )
-                total = cursor.fetchone()["total_messages"]
+        self.connect()
 
-                # Messages by company
-                cursor.execute(
-                    """
-                    SELECT company_name, COUNT(*) as count
-                    FROM llm_messages
-                    WHERE timestamp >= NOW() - INTERVAL '%s days'
-                    GROUP BY company_name
-                    ORDER BY count DESC
-                    LIMIT 10
-                    """,
-                    (days,),
-                )
-                by_company = cursor.fetchall()
+        with self.conn.cursor(cursor_factory=RealDictCursor) as cursor:
+            # Total messages
+            cursor.execute(
+                """
+                SELECT COUNT(*) as total_messages
+                FROM llm_messages
+                WHERE timestamp >= NOW() - INTERVAL '%s days'
+                """,
+                (days,),
+            )
+            total = cursor.fetchone()["total_messages"]
 
-                # Messages by type
-                cursor.execute(
-                    """
-                    SELECT analysis_type, COUNT(*) as count
-                    FROM llm_messages
-                    WHERE timestamp >= NOW() - INTERVAL '%s days'
-                    GROUP BY analysis_type
-                    ORDER BY count DESC
-                    """,
-                    (days,),
-                )
-                by_type = cursor.fetchall()
+            # Messages by company
+            cursor.execute(
+                """
+                SELECT company_name, COUNT(*) as count
+                FROM llm_messages
+                WHERE timestamp >= NOW() - INTERVAL '%s days'
+                GROUP BY company_name
+                ORDER BY count DESC
+                LIMIT 10
+                """,
+                (days,),
+            )
+            by_company = cursor.fetchall()
 
-                return {
-                    "total_messages": total,
-                    "by_company": [dict(row) for row in by_company],
-                    "by_type": [dict(row) for row in by_type],
-                    "period_days": days,
-                }
+            # Messages by type
+            cursor.execute(
+                """
+                SELECT analysis_type, COUNT(*) as count
+                FROM llm_messages
+                WHERE timestamp >= NOW() - INTERVAL '%s days'
+                GROUP BY analysis_type
+                ORDER BY count DESC
+                """,
+                (days,),
+            )
+            by_type = cursor.fetchall()
+
+            return {
+                "total_messages": total,
+                "by_company": [dict(row) for row in by_company],
+                "by_type": [dict(row) for row in by_type],
+                "period_days": days,
+            }
 
     # Patent Cache Methods
 
@@ -501,23 +505,25 @@ class DatabaseClient:
         Returns:
             Created user dict or None if email exists
         """
+        self.connect()
+
         password_hash = self.hash_password(password)
 
         try:
-            with self.get_conn() as conn:
-                with conn.cursor(cursor_factory=RealDictCursor) as cursor:
-                    cursor.execute(
-                        """
-                        INSERT INTO users (email, password_hash, role)
-                        VALUES (%s, %s, %s)
-                        RETURNING id, email, role, created_at
-                        """,
-                        (email, password_hash, role),
-                    )
-                    user = cursor.fetchone()
-                conn.commit()
+            with self.conn.cursor(cursor_factory=RealDictCursor) as cursor:
+                cursor.execute(
+                    """
+                    INSERT INTO users (email, password_hash, role)
+                    VALUES (%s, %s, %s)
+                    RETURNING id, email, role, created_at
+                    """,
+                    (email, password_hash, role),
+                )
+                user = cursor.fetchone()
+                self.conn.commit()
                 return dict(user) if user else None
         except psycopg2.errors.UniqueViolation:
+            self.conn.rollback()
             return None
 
     def authenticate_user(self, email: str, password: str) -> Optional[Dict]:
@@ -530,22 +536,23 @@ class DatabaseClient:
         Returns:
             User dict if authenticated, None otherwise
         """
-        with self.get_conn() as conn:
-            with conn.cursor(cursor_factory=RealDictCursor) as cursor:
-                cursor.execute(
-                    "SELECT * FROM users WHERE email = %s",
-                    (email,),
-                )
-                user = cursor.fetchone()
+        self.connect()
 
-                if user and self.verify_password(password, user["password_hash"]):
-                    return {
-                        "id": user["id"],
-                        "email": user["email"],
-                        "role": user["role"],
-                        "created_at": user["created_at"],
-                    }
-                return None
+        with self.conn.cursor(cursor_factory=RealDictCursor) as cursor:
+            cursor.execute(
+                "SELECT * FROM users WHERE email = %s",
+                (email,),
+            )
+            user = cursor.fetchone()
+
+            if user and self.verify_password(password, user["password_hash"]):
+                return {
+                    "id": user["id"],
+                    "email": user["email"],
+                    "role": user["role"],
+                    "created_at": user["created_at"],
+                }
+            return None
 
     def get_user_by_id(self, user_id: int) -> Optional[Dict]:
         """Get a user by ID.
@@ -556,14 +563,15 @@ class DatabaseClient:
         Returns:
             User dict or None
         """
-        with self.get_conn() as conn:
-            with conn.cursor(cursor_factory=RealDictCursor) as cursor:
-                cursor.execute(
-                    "SELECT id, email, role, created_at FROM users WHERE id = %s",
-                    (user_id,),
-                )
-                user = cursor.fetchone()
-                return dict(user) if user else None
+        self.connect()
+
+        with self.conn.cursor(cursor_factory=RealDictCursor) as cursor:
+            cursor.execute(
+                "SELECT id, email, role, created_at FROM users WHERE id = %s",
+                (user_id,),
+            )
+            user = cursor.fetchone()
+            return dict(user) if user else None
 
     def get_user_by_email(self, email: str) -> Optional[Dict]:
         """Get a user by email.
@@ -574,14 +582,15 @@ class DatabaseClient:
         Returns:
             User dict or None
         """
-        with self.get_conn() as conn:
-            with conn.cursor(cursor_factory=RealDictCursor) as cursor:
-                cursor.execute(
-                    "SELECT id, email, role, created_at FROM users WHERE email = %s",
-                    (email,),
-                )
-                user = cursor.fetchone()
-                return dict(user) if user else None
+        self.connect()
+
+        with self.conn.cursor(cursor_factory=RealDictCursor) as cursor:
+            cursor.execute(
+                "SELECT id, email, role, created_at FROM users WHERE email = %s",
+                (email,),
+            )
+            user = cursor.fetchone()
+            return dict(user) if user else None
 
     def get_all_users(self, limit: int = 100, offset: int = 0) -> List[Dict]:
         """Get all users (admin only).
@@ -593,18 +602,19 @@ class DatabaseClient:
         Returns:
             List of user dicts
         """
-        with self.get_conn() as conn:
-            with conn.cursor(cursor_factory=RealDictCursor) as cursor:
-                cursor.execute(
-                    """
-                    SELECT id, email, role, created_at
-                    FROM users
-                    ORDER BY created_at DESC
-                    LIMIT %s OFFSET %s
-                    """,
-                    (limit, offset),
-                )
-                return [dict(row) for row in cursor.fetchall()]
+        self.connect()
+
+        with self.conn.cursor(cursor_factory=RealDictCursor) as cursor:
+            cursor.execute(
+                """
+                SELECT id, email, role, created_at
+                FROM users
+                ORDER BY created_at DESC
+                LIMIT %s OFFSET %s
+                """,
+                (limit, offset),
+            )
+            return [dict(row) for row in cursor.fetchall()]
 
     def update_user_role(self, user_id: int, role: str) -> Optional[Dict]:
         """Update a user's role (admin only).
@@ -616,19 +626,20 @@ class DatabaseClient:
         Returns:
             Updated user dict or None
         """
-        with self.get_conn() as conn:
-            with conn.cursor(cursor_factory=RealDictCursor) as cursor:
-                cursor.execute(
-                    """
-                    UPDATE users
-                    SET role = %s, updated_at = CURRENT_TIMESTAMP
-                    WHERE id = %s
-                    RETURNING id, email, role, created_at
-                    """,
-                    (role, user_id),
-                )
-                user = cursor.fetchone()
-            conn.commit()
+        self.connect()
+
+        with self.conn.cursor(cursor_factory=RealDictCursor) as cursor:
+            cursor.execute(
+                """
+                UPDATE users
+                SET role = %s, updated_at = CURRENT_TIMESTAMP
+                WHERE id = %s
+                RETURNING id, email, role, created_at
+                """,
+                (role, user_id),
+            )
+            user = cursor.fetchone()
+            self.conn.commit()
             return dict(user) if user else None
 
     def delete_user(self, user_id: int) -> bool:
@@ -640,11 +651,12 @@ class DatabaseClient:
         Returns:
             True if deleted
         """
-        with self.get_conn() as conn:
-            with conn.cursor() as cursor:
-                cursor.execute("DELETE FROM users WHERE id = %s", (user_id,))
-                deleted = cursor.rowcount > 0
-            conn.commit()
+        self.connect()
+
+        with self.conn.cursor() as cursor:
+            cursor.execute("DELETE FROM users WHERE id = %s", (user_id,))
+            deleted = cursor.rowcount > 0
+            self.conn.commit()
             return deleted
 
     def get_user_count(self) -> int:
@@ -653,7 +665,8 @@ class DatabaseClient:
         Returns:
             Number of users
         """
-        with self.get_conn() as conn:
-            with conn.cursor() as cursor:
-                cursor.execute("SELECT COUNT(*) FROM users")
-                return cursor.fetchone()[0]
+        self.connect()
+
+        with self.conn.cursor() as cursor:
+            cursor.execute("SELECT COUNT(*) FROM users")
+            return cursor.fetchone()[0]

tests/test_auth.py

@@ -0,0 +1,302 @@
+"""Tests for JWT authentication flow: register, login, protected routes, refresh, admin access."""
+
+from datetime import datetime, timezone
+from unittest.mock import MagicMock, patch
+
+import pytest
+from fastapi.testclient import TestClient
+
+from SPARC.api import app
+from SPARC.auth import create_access_token, create_refresh_token
+
+
+@pytest.fixture
+def client():
+    """Create test client."""
+    return TestClient(app)
+
+
+@pytest.fixture(autouse=True)
+def mock_db(monkeypatch):
+    """Mock the database client used by auth endpoints.
+
+    Returns a MagicMock with all DB methods pre-configured.
+    """
+    db = MagicMock()
+
+    # Default: no users exist
+    db.get_user_count.return_value = 0
+    db.get_user_by_id.return_value = None
+    db.get_user_by_email.return_value = None
+    db.authenticate_user.return_value = None
+    db.create_user.return_value = None
+    db.get_all_users.return_value = []
+    db.update_user_role.return_value = None
+    db.delete_user.return_value = False
+
+    with patch("SPARC.api.get_db_client", return_value=db), \
+         patch("SPARC.auth.get_db_client", return_value=db):
+        yield db
+
+
+def _make_admin_user():
+    return {
+        "id": 1,
+        "email": "admin@test.com",
+        "role": "admin",
+        "created_at": datetime(2025, 1, 1, tzinfo=timezone.utc),
+    }
+
+
+def _make_regular_user():
+    return {
+        "id": 2,
+        "email": "user@test.com",
+        "role": "user",
+        "created_at": datetime(2025, 1, 1, tzinfo=timezone.utc),
+    }
+
+
+def _auth_header(user_dict):
+    """Create an Authorization header with a valid access token for the given user."""
+    token = create_access_token(user_dict["id"], user_dict["email"], user_dict["role"])
+    return {"Authorization": f"Bearer {token}"}
+
+
+class TestRegister:
+    """POST /auth/register"""
+
+    def test_register_first_user_becomes_admin(self, client, mock_db):
+        """First registered user should get admin role."""
+        mock_db.get_user_count.return_value = 0
+        mock_db.create_user.return_value = {
+            "id": 1,
+            "email": "admin@test.com",
+            "role": "admin",
+            "created_at": datetime(2025, 1, 1, tzinfo=timezone.utc),
+        }
+
+        response = client.post(
+            "/auth/register",
+            json={"email": "admin@test.com", "password": "securepass123"},
+        )
+
+        assert response.status_code == 200
+        data = response.json()
+        assert data["email"] == "admin@test.com"
+        assert data["role"] == "admin"
+        mock_db.create_user.assert_called_once_with(
+            email="admin@test.com", password="securepass123", role="admin"
+        )
+
+    def test_register_subsequent_user_gets_user_role(self, client, mock_db):
+        """Non-first user should get regular user role."""
+        mock_db.get_user_count.return_value = 1
+        mock_db.create_user.return_value = _make_regular_user()
+
+        response = client.post(
+            "/auth/register",
+            json={"email": "user@test.com", "password": "securepass123"},
+        )
+
+        assert response.status_code == 200
+        data = response.json()
+        assert data["role"] == "user"
+
+    def test_register_duplicate_email_returns_400(self, client, mock_db):
+        """Registering with an existing email should return 400."""
+        mock_db.get_user_count.return_value = 1
+        mock_db.create_user.return_value = None  # indicates duplicate
+
+        response = client.post(
+            "/auth/register",
+            json={"email": "existing@test.com", "password": "securepass123"},
+        )
+
+        assert response.status_code == 400
+        assert "already registered" in response.json()["detail"].lower()
+
+
+class TestLogin:
+    """POST /auth/login"""
+
+    def test_login_valid_credentials_returns_tokens(self, client, mock_db):
+        """Valid credentials should return access and refresh tokens."""
+        user = _make_regular_user()
+        mock_db.authenticate_user.return_value = user
+
+        response = client.post(
+            "/auth/login",
+            json={"email": "user@test.com", "password": "correctpassword"},
+        )
+
+        assert response.status_code == 200
+        data = response.json()
+        assert "access_token" in data
+        assert "refresh_token" in data
+        assert data["token_type"] == "bearer"
+
+    def test_login_invalid_credentials_returns_401(self, client, mock_db):
+        """Invalid credentials should return 401."""
+        mock_db.authenticate_user.return_value = None
+
+        response = client.post(
+            "/auth/login",
+            json={"email": "user@test.com", "password": "wrongpassword"},
+        )
+
+        assert response.status_code == 401
+        assert "invalid" in response.json()["detail"].lower()
+
+
+class TestGetMe:
+    """GET /auth/me"""
+
+    def test_valid_access_token_returns_user(self, client, mock_db):
+        """A valid access token should return the user's data."""
+        user = _make_regular_user()
+        mock_db.get_user_by_id.return_value = user
+
+        response = client.get("/auth/me", headers=_auth_header(user))
+
+        assert response.status_code == 200
+        data = response.json()
+        assert data["email"] == "user@test.com"
+        assert data["id"] == 2
+
+    def test_missing_token_returns_401(self, client):
+        """No token should return 401 (403 from HTTPBearer)."""
+        response = client.get("/auth/me")
+        assert response.status_code in (401, 403)
+
+    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",
+            "role": "user",
+            "exp": datetime.now(timezone.utc) - timedelta(hours=1),
+            "type": "access",
+        }
+        expired_token = pyjwt.encode(payload, JWT_SECRET, algorithm=JWT_ALGORITHM)
+
+        response = client.get(
+            "/auth/me", headers={"Authorization": f"Bearer {expired_token}"}
+        )
+        assert response.status_code == 401
+
+    def test_refresh_token_as_access_returns_401(self, client, mock_db):
+        """Using a refresh token as an access token should return 401."""
+        user = _make_regular_user()
+        refresh_token = create_refresh_token(user["id"], user["email"], user["role"])
+
+        response = client.get(
+            "/auth/me", headers={"Authorization": f"Bearer {refresh_token}"}
+        )
+        assert response.status_code == 401
+
+
+class TestRefreshToken:
+    """POST /auth/refresh"""
+
+    def test_valid_refresh_token_returns_new_tokens(self, client, mock_db):
+        """A valid refresh token should issue new access and refresh tokens."""
+        user = _make_regular_user()
+        mock_db.get_user_by_id.return_value = user
+        refresh = create_refresh_token(user["id"], user["email"], user["role"])
+
+        response = client.post(
+            "/auth/refresh", json={"refresh_token": refresh}
+        )
+
+        assert response.status_code == 200
+        data = response.json()
+        assert "access_token" in data
+        assert "refresh_token" in data
+
+    def test_invalid_refresh_token_returns_401(self, client, mock_db):
+        """An invalid refresh token should return 401."""
+        response = client.post(
+            "/auth/refresh", json={"refresh_token": "invalid-token-string"}
+        )
+        assert response.status_code == 401
+
+    def test_access_token_as_refresh_returns_401(self, client, mock_db):
+        """Using an access token as a refresh token should return 401."""
+        user = _make_regular_user()
+        access = create_access_token(user["id"], user["email"], user["role"])
+
+        response = client.post(
+            "/auth/refresh", json={"refresh_token": access}
+        )
+        assert response.status_code == 401
+
+
+class TestAdminUsers:
+    """GET /admin/users and PATCH /admin/users/{id}/role"""
+
+    def test_admin_can_list_users(self, client, mock_db):
+        """Admin token should allow listing users."""
+        admin = _make_admin_user()
+        mock_db.get_user_by_id.return_value = admin
+        mock_db.get_all_users.return_value = [admin, _make_regular_user()]
+
+        response = client.get("/admin/users", headers=_auth_header(admin))
+
+        assert response.status_code == 200
+        data = response.json()
+        assert len(data) == 2
+
+    def test_regular_user_cannot_list_users(self, client, mock_db):
+        """Regular user token should be rejected with 403."""
+        user = _make_regular_user()
+        mock_db.get_user_by_id.return_value = user
+
+        response = client.get("/admin/users", headers=_auth_header(user))
+
+        assert response.status_code == 403
+
+    def test_no_token_cannot_list_users(self, client):
+        """No token should be rejected."""
+        response = client.get("/admin/users")
+        assert response.status_code in (401, 403)
+
+    def test_admin_can_change_user_role(self, client, mock_db):
+        """Admin should be able to change another user's role."""
+        admin = _make_admin_user()
+        mock_db.get_user_by_id.return_value = admin
+        mock_db.update_user_role.return_value = {
+            "id": 2,
+            "email": "user@test.com",
+            "role": "admin",
+            "created_at": datetime(2025, 1, 1, tzinfo=timezone.utc),
+        }
+
+        response = client.patch(
+            "/admin/users/2/role",
+            json={"role": "admin"},
+            headers=_auth_header(admin),
+        )
+
+        assert response.status_code == 200
+        assert response.json()["role"] == "admin"
+
+    def test_admin_cannot_change_own_role(self, client, mock_db):
+        """Admin should not be able to change their own role."""
+        admin = _make_admin_user()
+        mock_db.get_user_by_id.return_value = admin
+
+        response = client.patch(
+            "/admin/users/1/role",
+            json={"role": "user"},
+            headers=_auth_header(admin),
+        )
+
+        assert response.status_code == 400
+        assert "own role" in response.json()["detail"].lower()