Food fills English idioms. Complete this one for 'very easy': 'The test was a piece of ___.'

"A piece of cake" is the correct idiom meaning something is very easy to do, drawing on the image of cake being pleasant, simple, and effortless to eat compared to more difficult foods. English frequently uses food imagery to describe abstract concepts like difficulty, and cake's association with treats and celebration made it a natural symbol for ease.

"Pie" and "bread" don't complete this particular fixed idiom, even though pie appears in other idioms like "easy as pie," which carries the same meaning through a different fixed phrase — the two idioms simply aren't interchangeable in their exact wording.

English has a whole cluster of food-based idioms for easy tasks, including "easy as pie" and "a walk in the park," showing how everyday pleasant experiences repeatedly get recruited as metaphors for effortlessness across the language.