Updated the test system

test/lowercaseKeys.test.js

@@ -0,0 +1,14 @@
+const expect = require('expect');
+const {lowercaseKeys} = require('./_30s.js');
+
+test('lowercaseKeys is a Function', () => {
+  expect(lowercaseKeys).toBeInstanceOf(Function);
+});
+const myObj = { Name: 'Adam', sUrnAME: 'Smith' };
+const myObjLower = lowercaseKeys(myObj);
+test('Lowercases object keys', () => {
+  expect(myObjLower).toEqual({ name: 'Adam', surname: 'Smith' });
+});
+test('Does not mutate original object', () => {
+  expect(myObj).toEqual({ Name: 'Adam', sUrnAME: 'Smith' });
+});