A one page business model canvas let's you capture the key assumptions or hypotheses that underlie your business model. There are multiple kinds of 1 page canvas. The original one is described in the book Business Model Generation. (Download a PDF of the canvas here.) There's even an iPad app that makes it easy and fun to work through.
Another option is the Lean Canvas, developed by Ash Maurya and described him his book Running Lean. (Download a PowerPoint of the lean canvas here.)
There are at least two online courses about testing your business model using a 1 page Business Model Canvas. You'll find them at these links:
Online Startup Camp (by OTBC; uses the Lean Canvas)
Udacity-How to Build a Startup (by Steve Blank, uses the original canvas)
Remember - what you capture in the 1 page canvas are your beliefs. Assumptions. They all need to be tested - before you create your product or service! You'll save yourself a lot of time and pain if you test first, code later!