Migrated tests to jest

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

test/isSorted/isSorted.js

@@ -1,9 +0,0 @@
-const isSorted = arr => {
-let direction = -(arr[0] - arr[1]);
-for (let [i, val] of arr.entries()) {
-direction = !direction ? -(arr[i - 1] - arr[i]) : direction;
-if (i === arr.length - 1) return !direction ? 0 : direction;
-else if ((val - arr[i + 1]) * direction > 0) return 0;
-}
-};
-module.exports = isSorted;