Not sure what kind of save system you used, but the save system plugin was helpful, both for me, and for alpha testers who sometimes had internet issues. Saving every few pages helped a few of them not have to restart again and again.
For my longer game, I made a few general character-presets and made a separate 'game', and then just dropped whatever chapter I wanted to test into that game.
Like @Havenstone, I eventually put a 'jump to chapter' option at the beginning of my public alpha demo for alpha testers who just wanted to retry a certain scene, and offered a handful of preset character types there too.
Nowadays though, with @CJW's upcoming CSIDE, I use the console to jump to whatever scene and label I want (or change variables, even). It's still in closed beta currently, but it will, we hope, launch in the near future.