src/third_party/mozjs-45/js/src/jit-test/tests/debug/Frame-environment-02.js

// dbg.getNewestFrame().environment works.

var g = newGlobal();
var dbg = new Debugger;
var gw = dbg.addDebuggee(g);
g.h = function () {
    var env = dbg.getNewestFrame().environment.parent.parent;
    assertEq(env instanceof Debugger.Environment, true);
    assertEq(env.object, gw);
    assertEq(env.parent, null);
};
g.eval("h()");