foamy chicken poop (picture attached) - what causes this?

[SeaChickens]

My hen let out this crazy foamy yellow poop this morning. She seems normal otherwise, eating, drinking, laying eggs and acting normal. Does anyone know what would cause this? I had a fecal test done on another hen in my flock a few weeks ago and they didn't find any evidence of worms or cocci. She had also had some foamy poops but not as dramatic as this one.

 

[Eggcessive]

That looks like a cecal dropping, which occurs once in awhile. She may be drinking a lot of water to make it more runny. Here are a few examples below of cecal droppings:

 

[SeaChickens]

Thanks @Eggcessive!
I think that must be it. The hens have been free ranging so maybe that is why it's bigger and frothier than normal. So much different than my original flock's cecal poops which is what had me worried.