I've run into a bug where mother.children.length != mother.children.to_a.length in certain situations. A test-case built from a fresh rails-repository is referenced below.

To reproduce
1. Setup a mother with associated children
2. call mother.children.any?
3. Iterate over the children using render @mother.children
4. watch how mother.children.length != mother.children.to_a.length

The problem is related to
Mongoid::Relations::Targets::Enumerable

Test case
Let me know if I should elaborate on how to reproduce the bug. But since it's just a bare Rails repo with minimum new files it shouldn't be too hard to figure it out.

https://github.com/sandstrom/Mongoid-Bug