There are a lot of easy tests and many don't involve cameras or lenses at all.
For instance look down a long line of telephone poles or trees and from your starting position notice how big say the second, third and fourth pole look in relationship to the one closest to you. Then walk half the distance to the first pole and notice how large it looks compared to those further back, then walk right up to the first pole and notice it's huge and fills your view but the others have stayed relatively normal sized. That's all based on relative distance to each element in your scene and not based on what lens you happen to capture the scene with.
Similarly go up to bathroom mirror, close one eye as stereo vision messes with this a bit and move your face closer and closer to the mirror. Notice how your facial features distort and the nose starts to get huge compared to say the ears or eyes. That's also a perspective issue and not really 'distortion' created by shooting portraits with ultra wide angle lenses as much as being very close to a three dimensional face so parts (e.g. the nose) are extremely close and other parts like the eyes are relatively farther back.
Bill said it very well above, it's all about the relative distances between individual elements in your scene.
So if you're 100' from the closest object and 110' to a slightly more distant object of the same size they'll look fairly similar with the distant object 110% the distance to the close object or IOW, the second object will look roughly 90% of the size of the closer same sized object. But now walk up close so you're 10' away from the close object and 20 feet away from the more distant object and that second object will be twice as far away and look around 50% of the size of the closer object.
The choice of lens lets you optically crop so the main image element is the size you want in the frame but it's your relative distance to each element in the scene that determines perspective or IOW, the relative size of each element in the scene to each other. That compression folks talk about with long lenses is just because we tend to work at long distances with those lenses and the facial distortions some photographers talk about with ultra wide angle lenses is just because we tend to work at very close distances with ultra wide angle lenses to get the subject size we're after. But in both cases the perspective comes from our working distance, not the lens itself though the lens does allow us to optically crop the scene so that the main elements fit or are as large as desired in the frame.
In workshops we talk about finding perspective with your feet and then framing the scene by choosing an appropriate focal length.
