gistfile1.js

testBoth('should fire observer that contains a path', function(get, set) {
  var CarMixin = SC.Mixin.create({
    acceleration: 0
  });

  var car = SC.mixin({}, CarMixin);

  var tireAcceleration;

  var TireMixin = SC.Mixin.create({
    accelerationDidChange: SC.observer(function() {
      tireAcceleration = get(this, 'car.acceleration');
    }, 'car.acceleration')
  });

  var tire = SC.mixin({
    car: car
  }, TireMixin);

  set(car, 'acceleration', 50);

  equals(tireAcceleration, 50, "observer should fire");
});