Trying out and testing are basically the same thing. Usually when making a new material we have a thing of what properties it should have (should it be hard/soft bendy/brittle), and we can use useful chemical knowledge to “program” the reaction like a computer program, so we get a material with the qualities that we want. Sometimes this does not work as well as we would hope.
Testing usually would involve:
Density: Density is how much something weighs for a measured voulme. A tonne of bricks and a tonne of feathers have the same MASS, but feathers have a LOWER density than bricks.
Strength: How much bending/stretching can it take before it snaps, or bends so much it will never go back to normal.
Hardness: Will it scratch if you rubbed it with a sharp nail etc
We would as test for inner strength – would it break into millions of pieces if you were to drop it.