Migrated tests to jest

Used jest-codemods to migrate, will have to pass everything by hand before we can merge.

test/permutations/permutations.js

@@ -1,11 +0,0 @@
-const permutations = arr => {
-if (arr.length <= 2) return arr.length === 2 ? [arr, [arr[1], arr[0]]] : arr;
-return arr.reduce(
-(acc, item, i) =>
-acc.concat(
-permutations([...arr.slice(0, i), ...arr.slice(i + 1)]).map(val => [item, ...val])
-),
-[]
-);
-};
-module.exports = permutations;