Você pode usar o comando diff
:
#! /bin/bash
for dir in testcases/*
do
if [[ -d $dir ]]
then
cd $dir
diff testcase.csv testcase64.csv -q > /dev/null || echo "$dir/testcase.csv and $dir/testcase64.csv differ."
diff testcase.csv testcaseMac.csv -q > /dev/null || echo "$dir/testcase.csv and $dir/testcaseMac.csv differ."
diff testcaseMac.csv testcase64.csv -q > /dev/null || echo "$dir/testcaseMac.csv and $dir/testcase64.csv differ."
cd -
fi
done