Can we create a zero-simulation test using actual composer commands on DrupalCI?

I this would be great but doesn't absolutely have to be done by core-mvp

I think this one is pretty fixed. Our tests no longer do much simulating, except the more unit-level kernel tests for individual validators. Our fixture manipulator calls actual Composer commands; build tests have always used Composer for real, on an unsimulated, albeit simple, project.

So I think this can be closed as outdated.