In that example sentence, very is an adverb, easy is an adjective.
Ex: The test is very easy.
Let's check it
=> test is a noun. We know this because nouns take determiners/articles and a is one.
an easy test
=> We know that test is a noun, and that nouns are modified by adjectives, which makes easy and adjective.
a very easy test
=> We know that easy is an adjective, and that adjectives are modified by adverbs, which makes very an adverb.