The typical cognitive assessments that are used for children require them to be able to use their hands to point to pictures or hold puzzle pieces.
For a child with CP learning to move, the really important things to remember are that the child should always be active.
Spasticity is a condition of muscles that is a velocity resistance to stretch. What that means to a child and to a parent is that if you move the limb slowly, you have a difference than if you move that limb fast. Spasticity restricts movement and it creates a break on the system. It's as if they're trying to move, but they're held back. By treating spasticity, you may improve the range of motion or the action of the movement.
Every educator needs to make a decision about technology they need to put in place. They're not sure if they should put Option A in place or Option B in place. This can be particularly difficult in the world of disabilities because there might not always be a perfect answer. Teachers can look to this solution, using the least dangerous assumption to make good decisions about what technology might be best.
When you don't have enough evidence about a student's performance, assume they can do whatever you're asking them to do.