mongoid/mongoid — pull request #2334 by jpmckinney (2012-08-31 19:24:36+00:00)
Title: Add specs to exhibit strange behavior when aggregating on field that doesn't always exist

When a field only *sometimes* exists, the aggregates behave oddly. In both the specs, `50` should be the min. But in one case it's `nil` and in another it's `100` (!).