fakemongo/fongo — pull request #82 by libetl (2014-12-31 15:37:02+00:00)
Title: .$ operation is not working well, it must add or replace a value in an a array

I found out that this operation {"$set" : { "parentObject.subObject.$" : { "_id" : "random1" , "var3" : "val33"}}}
works with mongoDB but does not work with fongoDB. We must update the array instead of appending the parent object.

I added an unit test to emphazise that problem.