I've discussed before how "made of" is used for gapfill questions in the Listening Test.
'Made of' and 'made from' are also used quite frequently in the Reading Test, as you can see in the example below from Lesson 8 of my Reading Skills Course all about gapfill summaries:
[Don't worry too much about the differences - people mix them up all the time]
Made of : when the material doesn't change during the process of making the item e.g.
Made from: when the material changes (usually when something is manufactured) e.g.
Check you understand the rule by looking at these sentences, then test yourself with the gaps below.
Also:
You use made out of to talk about something that has been changed or transformed from one thing into another:
e.g Homeless people often sleep in tents made out of cardboard boxes.
You use made with to talk about the ingredients of food and drink:
In the UK, sushi always made with cooked fish, for health and safety reasons.