A glucose test measures the amount of sugar/glucose in your blood. Insulin is thing that transports the sugar from your blood to your cells so they are nourished. An insulin test will determine whether or not your pancreas is making insulin. Hope that helps.
By the way...
Having extra insulin is a sign of insulin resistance which may lead to type 2 diabetes, high glucose levels show insulin resistance, type 2 or pcos. Limit the refined carbs to lower glucose.