Emma is generally compliant too but around that age she started testing her limits. Now when she tells me no to something I ask her if she wants me to turn the TV off (if it's on) or if she needs a time out in the hallway and she says, "NO" and will do what I've asked her about 90% of the time. She's tested the limits already and she knows that I will follow through so it does get better if you stay consistent. Punker will realize that you mean business and will stop pushing in time. Hang in there!