how to do async test(pytest) in fastapi with error `There is 1 other session using the database` - asynchronous

Question

While I was writing the Async test code for FASTAPI there is a problem that cannot be solved. this code is for test db. I'm using postgres and in order to user db as a test, I created is_testing function. It drop and create test db.
if is_testing:
db_url = self._engine.url
if db_url.host != "localhost":
raise Exception("db host must be 'localhost' in test environment")
except_schema_db_url = f"{db_url.drivername}://{db_url.username}#{db_url.host}"
schema_name = db_url.database # test
temp_engine = create_engine(except_schema_db_url, echo=echo, pool_recycle=pool_recycle, pool_pre_ping=True)
conn = temp_engine.connect()
try:
conn = conn.execution_options(autocommit=False)
conn.execute("ROLLBACK")
conn.execute(f"DROP DATABASE {schema_name}")
except ProgrammingError:
print(f"could not drop the database, probably does not exist.")
conn.execute("ROLLBACK")
except OperationalError:
print("could not drop database because it's being accessed by other users(psql prompt open?)")
conn.execute("ROLLBACK")
print(f"test db dropped! about to create {schema_name}")
conn.execute(f"CREATE DATABASE {schema_name}")
try:
conn.execute(f"create user test with encrypted password test")
except:
print("User already exist")
temp_engine.dispose()
this is conftest.py
#pytest.fixture(scope="session")
def app():
os.environ["API_ENV"] = "test"
return create_app()
#pytest.fixture(scope="session")
def client(app):
Base.metadata.create_all(db.engine)
# Create tables
client = AsyncClient(app=app, base_url="http://test")
return client
#pytest.fixture(scope="function", autouse=True)
def session():
sess = next(db.session())
yield sess
clear_all_table_data(
session=sess,
metadata=Base.metadata,
except_tables=[]
)
sess.rollback()
def clear_all_table_data(session: Session, metadata, except_tables: List[str] = None):
session.execute("SET session_replication_role = 'replica';")
for table in metadata.sorted_tables:
if table.name not in except_tables:
session.execute(table.delete())
session.execute("SET session_replication_role = 'origin';")
session.commit()
I got error sqlalchemy.exc.OperationalError: (psycopg2.errors.ObjectInUse) database "test" is being accessed by other users DETAIL: There is 1 other session using the database. in elb check test.
and I got error TypeError: 'AsyncClient' object is not callable in another api test.
I modified client function in conftest.py
#pytest.fixture(scope="session")
def client(app):
Base.metadata.create_all(db.engine)
return AsyncClient(app=app, base_url="http://test")
I passed one test, but I received the following error from the second test.
ClientState.OPENED: "Cannot open a client instance more than once.",
ClientState.CLOSED: "Cannot reopen a client instance, once it has been closed.",
how can I fix it?
thank you for reading long question!