sinon

HTML

<script src="http://sinonjs.org/releases/sinon-1.7.1.js"></script>

JavaScript

var A = function() {};

A.getInstance = function() {
	return new A();
}

A.prototype.render = function() {
	return this;
}

A.prototype.show = function() {}
var c = {
	render: sinon.stub().returns(c),
  show: sinon.stub()
};

sinon.stub(A, 'getInstance').returns({
render: sinon.stub(function() {return this}),
show: sinon.stub()
});

function f() {
	A.getInstance().render().show();
}
f();
console.log(A.getInstance.callCount);