I think if you take a lot at the motivations that Dan Abramov had for creating Redux [1], you'll see that improving debugging was at the centre of it. Check out his talk he gave at React-Europe. He basically is talking about improving developer tools. The functional approach Redux takes allows for you to see state transitions and replay actions - making it relatively trivial (compared to say Angular.js) to understand how to reproduce a buggy state.
Dude, this is half the point of redux. Theres a debugger that lets you visually step through every state of the store and your corresponding app - https://github.com/gaearon/redux-devtools
[1] https://github.com/rackt/redux
[2] https://www.youtube.com/watch?v=xsSnOQynTHs