Use the PEST (or PESTLE analysis to understand your macro environment).
The PEST or PESTEL-analysis gives you an overview of the external forces that surrounds you idea and business. Thereby you will get an idea about the size of the opportunities and the seriousness of the threats you are facing.
Do the PEST-analysis in particular in the Test-phase. It will help you evaluate the overall business opportunity and assess potential risks.
In an article at Mindtools you can read more about the process: