Click: Test click.group commands without running their code

I´m currently writing tests for my application and therefore, I have to test some click.group commands I defined:

Let´s say I defined them like:

@click.group(cls=MyGroup)
@click.pass_context
def myapp(ctx):
    init_stuff()    

@myapp.command()
@click.option('--myOption')
def foo(myOption: str) -> None:
    do_stuff() # change some files, print, create other files

I know that I could use the CliRunner from click.testing. However, I just want to make sure, that the command is called, but I DONT WANT it to execute any code (for example by applying the CliRunner.invoke()).

How could this be done? I couldn´t come up with a solution using mocking with foo for example. Or do I have to execute code lets say using the isolated_filesystem() which CliRunner provides?

So the question is: What would be the most efficient way to test my commands when defined like shown above?

Many thanks in advance