very easy in English:

This test was just a piece of cake.

making it was piece of cake

The exam was a piece of cake

This is simply a piece of cake for me! I have always been good at maths.

You’ll learn the recipe without a problem. It’s a piece of cake!

I don't know why you are so worried. I thought the exam was a piece of cake.

It was a piece of cake!

- How was the exam? - It was a piece of cake!

The test was a piece of cake.