The Tor Browser / file revision

 // Debugger.Object basics

 var g = newGlobal();

 var dbg = Debugger(g);

 var hits = 0;

 dbg.onDebuggerStatement = function (frame) {

     assertEq(frame.arguments[0], frame.callee);

     assertEq(Object.getPrototypeOf(frame.arguments[0]), Debugger.Object.prototype);

     assertEq(frame.arguments[0] instanceof Debugger.Object, true);

     assertEq(frame.arguments[0] !== frame.arguments[1], true);

     assertEq(Object.getPrototypeOf(frame.arguments[1]), Debugger.Object.prototype);

     assertEq(frame.arguments[1] instanceof Debugger.Object, true);

     hits++;

 };

 g.eval("var obj = {}; function f(a, b) { debugger; } f(f, obj);");

 assertEq(hits, 1);