The relationship between testfixture and gz instruction

I want to know if I can create a Gazebo node using testfixture in Python and run it, and then use the gz service – list command to get the corresponding information. But when I tried to add the model using commands like gz service/world/name/create, although the return result was true, the gz service - s/world/name/scene/info command gave me the result that I did not successfully add the model to the world. The remove command also failed. I would like to know if it is possible to use the gz command to interact with the testfixture node? If possible, please tell me the relevant details and methods.
My current process is:
self.fixture = TestFixture(self.world_path)
self.fixture.finalize()
self.server = self.fixture.server()
self.server.run(True, 1000, False)
Then start executing various gz instructions. I can guarantee that the syntax of the instructions I execute is correct, but they (mainly instructions that modify Gazebo itself) cannot take effect properly.
Moreover, the gz model – list cannot be used for creating gazebo nodes for testfixture. I would like to know if this is normal? It always prompts me that a certain service has timed out.