Updated the test system

test/deepFreeze.test.js

@@ -0,0 +1,35 @@
+const expect = require('expect');
+const {deepFreeze} = require('./_30s.js');
+
+test('deepFreeze is a Function', () => {
+  expect(deepFreeze).toBeInstanceOf(Function);
+});
+
+test('modifying deeply freezed object prop throws an error in strict mode', () => {
+  let freezedObj = deepFreeze({ a: 42 });
+
+  expect(() => {
+    'use strict';
+    freezedObj.a = 24;
+  }).toThrow();
+});
+
+test('should not modify deeply freezed object inside another object', () => {
+  let freezedObj = deepFreeze({
+    a: {
+      b: 42
+    }
+  });
+
+  freezedObj.a.b = 16;
+
+  expect(freezedObj.a.b).toBe(42);
+});
+
+test('should not add prop to deeply freezed empty object', () => {
+  let freezedObj = deepFreeze({});
+
+  freezedObj.a = 42;
+
+  expect(freezedObj).toEqual({});
+});