cause error when argument don't have a default constructor

[ianhe8x]

I mocked a method which is called with a argument don't have a default constructor. in MethodInvocation's constructor

if (args) {
      this._args = <any>_.cloneDeep(args);
      this._args.length = args.length;
      this._args.callee = args.callee;
}

and then cause my application throw error.

So why cloneDeep the arguments? Is there any workaround in this case?