Is testing good thing? Yes! Then do it all the time!
"Testing phase" is a term from waterfall projects.
In agile (I assume you trying to be agile since you are setting up as a scrum team) you are focused on being able to adapt and adopt quickly - testing is the key in that process.
Do it often and do it all the time - feedback will be provided often and team will be able to adopt quickly and timely.
Creating a testing phase (whenever it is scheduled for) - you will slip into waterfall mode or better yet - scrumfall. Think about the feedback - at the end of the 'testing [phase' which some after many other phases. Lots of waste that you trying to avoid by being agile and by using scrum.
There are no people with primary skills being testing - it does not matter - let them learn how to test their product/application. Invest time (and money) in that - it will pay off big time as they move forward.