Migrated tests to jest

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

test/lowercaseKeys/lowercaseKeys.js

@@ -1,6 +0,0 @@
-const lowercaseKeys = obj =>
-Object.keys(obj).reduce((acc, key) => {
-acc[key.toLowerCase()] = obj[key];
-return acc;
-}, {});
-module.exports = lowercaseKeys;