What I expected to happen was: Become invincible with the /effect command.

What actually happened was when I got the health boost effect level 255, the screen started shaking, when I stopped the effect, the shaking stopped.

Steps to Reproduce:
1. Make sure you have Minecraft PC and you are on the 1.9 snapshot 15w45a
2. Make sure you are on creative mode and have cheats enabled in the world.
3. Use this command: /effect @p 21 1000000 255, and then you are done!