Migrated tests to jest

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

test2/dropWhile/dropWhile.js

@@ -0,0 +1,5 @@
+const dropWhile = (arr, func) => {
+while (arr.length > 0 && !func(arr[0])) arr = arr.slice(1);
+return arr;
+};
+module.exports = dropWhile;