Test: wrap test creation in functions

[aminya]

Test: create the renderer and package test only if needed. This speeds up test env preparation.

Verification

Just wraps the code in functions.

Continuation of #50

[DeeDeeG]

This seems good to me. 👍

Technical note: Not just GitHub, but Git itself will think this has a huge diff. So sadly this small change can expose us to merge conflicts. It is what it is, no real way around it, other than hopefully upstreaming this eventually. Edit to add: Everything we do can expose us to merge conflicts. It's no big deal; if we understand how the code works, merge conflicts are easy to solve.