Roughly it took us around 8–10 weeks but we had other projects going at the same time so it wasn’t fully working on this project for 8–10 weeks flat.
In regards to testing it will be hard to tell all the details here in a response(maybe we should write an article about how we test) but there are a few types. One is basic user testing, doing workshops and recording their faces/actions and seeing how well they perform tasks and getting data/results through there. Another is A/B testing, trying 2 different versions of copy, images etc for 24 hours then another 24 hours testing out the alt version and seeing which worked better in terms of more signs ups. We used Mixpanel for collecting data/patterns etc. I would recommend checking that out further.
Hope this helps :)