Is there any way to test out PS1 Bash Prompts before committing them?

You could create a file with your "new prompt" tweaks and then source it from the command line.

 vim new_prompt.bash
 source ./new_prompt.bash

The new prompt will only be active in that shell. If you open a new shell, your old prompt will be sourced and set.

When you are ready to 'commit' the new prompt, just add it to your bash initialization scripts.

EDIT:

I also just found this online bash prompt preview. I don't know what version of bash it's based on.