I'm experiencing an error in the tests for mongoid 3.0.0. After bundle install, I'm doing bundle exec rspec spec/*/_spec.rb --no-color --fail-fast.

$ git log
commit eeb4a88bd77514e8aeb99866794b0d8132a0ac12
Date:   Sat Mar 9 17:06:55 2013 -0500

$ cat rspec-filtered
Run options: exclude {:config=>#<Proc:./spec/spec_helper.rb:73>}
Mongoid::Criteria
  #aggregates
    when provided a single field
      returns an avg (FAILED - 1)
Failures:
  1) Mongoid::Criteria#aggregates when provided a single field returns an avg
     Failure/Error: criteria.aggregates(:likes)
     NoMethodError:
       undefined method `[]' for nil:NilClass
     # ./lib/mongoid/contextual/aggregable/mongo.rb:27:in `aggregates'
     # ./lib/mongoid/contextual.rb:10:in `aggregates'
     # ./spec/mongoid/criteria_spec.rb:149:in `block (4 levels) in <top (required)>'
     # ./spec/mongoid/criteria_spec.rb:153:in `block (4 levels) in <top (required)>'
Finished in 16.64 seconds
758 examples, 1 failure
Failed examples:
rspec ./spec/mongoid/criteria_spec.rb:152 # Mongoid::Criteria#aggregates when provided a single field returns an avg

I'm using mongodb 2.0.0, the latest in Debian squeeze backports:

$ dpkg-query -l mongodb
mongodb 1:2.0.0-2~bpo60+1

$ cat /etc/mongodb.conf

1. mongodb.conf

1. Where to store the data.

1. Note: if you run mongodb as a non-root user (recommended) you may
2. need to create and set permissions for this directory manually,
3. e.g., if the parent directory isn't mutable by the mongodb user.
   dbpath=/var/lib/mongodb

#where to log
logpath=/var/log/mongodb/mongodb.log

1. logappend=true
   logappend=false

bind_ip = 127.0.0.1
#port = 27017

1. Enables periodic logging of CPU utilization and I/O wait
   #cpu = true

1. Turn on/off security. Off is currently the default
   #noauth = true
   #auth = true

1. Verbose logging output.
   #verbose = true

1. Per http://stackoverflow.com/questions/5004626/mongod-log-file-growth
   quiet = true

1. Inspect all client data for validity on receipt (useful for
2. developing drivers)
   #objcheck = true

1. Enable db quota management
   #quota = true

1. Set oplogging level where n is
2. 0=off (default)
3. 1=W
4. 2=R
5. 3=both
6. 7=W+some reads
   #oplog = 0

1. Diagnostic/debugging option
   #nocursors = true

1. Ignore query hints
   #nohints = true

1. Disable the HTTP interface (Defaults to localhost:27018).
   #nohttpinterface = true

1. Turns off server-side scripting. This will result in greatly limited
2. functionality
   #noscripting = true

1. Turns off table scans. Any query that would do a table scan fails.
   #notablescan = true

1. Disable data file preallocation.
   noprealloc = true

1. Specify .ns file size for new databases.
2. nssize = <size>
   nssize = 2

1. Accout token for Mongo monitoring server.
   #mms-token = <token>

1. Server name for Mongo monitoring server.
   #mms-name = <server-name>

1. Ping interval for Mongo monitoring server.
   #mms-interval = <seconds>

1. Replication Options

1. in replicated mongo databases, specify here whether this is a slave or master
   #slave = true
   #source = master.example.com
2. Slave only: specify a single database to replicate
   #only = master.example.com
3. or
   #master = true
   #source = slave.example.com

1. Address of a server to pair with.
   #pairwith = <server:port>
2. Address of arbiter server.
   #arbiter = <server:port>
3. Automatically resync if slave data is stale
   #autoresync
4. Custom size for replication operation log.
   #oplogSize = <MB>
5. Size limit for in-memory storage of op ids.
   #opIdMem = <bytes>