Migrated tests to jest

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

test4/isValidJSON/isValidJSON.js

@@ -0,0 +1,9 @@
+const isValidJSON = obj => {
+try {
+JSON.parse(obj);
+return true;
+} catch (e) {
+return false;
+}
+};
+module.exports = isValidJSON;