Updated the test system

test/cleanObj.test.js

@@ -0,0 +1,10 @@
+const expect = require('expect');
+const {cleanObj} = require('./_30s.js');
+
+test('cleanObj is a Function', () => {
+  expect(cleanObj).toBeInstanceOf(Function);
+});
+const testObj = { a: 1, b: 2, children: { a: 1, b: 2 } };
+test('Removes any properties except the ones specified from a JSON object', () => {
+  expect(cleanObj(testObj, ['a'], 'children')).toEqual({ a: 1, children: { a: 1 } });
+});