step_context not provided in build_output_context for test unit

[dridk]

Hi,

I m making test unit with pytest to check an IoManager.
I m doing this :

with build_output_context(asset_key= ["bob"]) as context: 
        manager = MyIOManager()
        manager.handle_output(context) 

It works for most the the time except if I try to access context.asset_spec from MyIOManager.
It tells me :
dagster._core.errors.DagsterInvariantViolationError: Attempting to access step_context, but it was not provided when constructing the OutputContext

How can I moke the step_context ?