Having a software or App come to market has many stages before it reaches the user testing stage. With many Apps we like to get as much user testing from specific personas that would be engaging your software build and find out their behaviours, user experience and unbiased opinions.  Having sites such as usertesting.com allows for the tapping of millions of different user types right down to your own specific user type persona. This helps generate very valuable feedback that can be pushed right back into the prototype and fix issues before you go live. This qualitative feedback helps optimize user experience, provide optimization and get the most out you client relationship. You get real videos of people engaging the software and speaking their thoughts as they use the software. This feedback is the true test of your prototype from your exact target audience and can be done in less than 1hr sometimes. You can recruit users by region, income, gender, expertise and more to have a match to your Personas that have been built in the earlier stages of the user centred design process. The users have their own devices that allows you to see a variety of results from different platforms and browsers. Having user feedback during your prototype phase ensures before you launch you have a clean UX and area truly ready for market.