add mocha test

Author: Deng

test/test.js

@@ -0,0 +1,8 @@
+var assert = require('assert');
+describe('Array', function() {
+  describe('#indexOf()', function() {
+    it('should return -1 when the value is not present', function() {
+      assert.equal([1, 2, 3].indexOf(4), -1);
+    });
+  });
+});