Rspec: Testing MongoMapper query

Question

I have a method:

def fb_matches_for_friend_employer_goals(user, friend)
    User.where( :is_reachable_on_fb   => true,                          # Users that are reachable on FB via wall posts
                "jobs.employer"       => friend.interested_employers,   # Users that have worked at the employers the friend is interested
                :fb_user_id           => user.fb_connections,           # Users that are friends of user through FB
                :fb_user_id.nin       => friend.fb_connections,         # Users that are NOT friends with the friend through FB
                :fb_user_id.ne        => user.fb_user_id,               # Users that are NOT the user
                :fb_user_id.ne        => friend.fb_user_id              # Users that are NOT the friend (although it's likely the friend hasn't worked at the goal employer)
    ).fields(:id, :jobs, :fb_connections).all
  end 

And a test:

  describe "#fb_matches_for_friend_employer_goals method" do
    let(:friend) { stub_model(User) }

    before(:each) do
      User.stub(where: User, fields: User, all: User)
      friend.stub(interested_employers: ["Apple"])
      friend.stub(fb_connections: ["100", "200"])
      friend.stub(fb_user_id: "1")        
      user.stub(fb_connections: ["101", "201"])
      user.stub(fb_user_id: "2")
    end

    it "returns users that are reachable on FB" do
      User.should_receive(:where).with( :is_reachable_on_fb   => true,
                                        "jobs.employer"       => ["Apple"],
                                        :fb_user_id           => ["101", "201"],
                                        :fb_user_id.nin       => ["100", "200"],
                                        :fb_user_id.ne        => "2",
                                        :fb_user_id.ne        => "1")
      a.fb_matches_for_friend_employer_goals(user, friend)
    end

  end

I get the following error:

Failures:

    1) Algorithm::Helpers::Facebook#fb_matches_for_friend_employer_goals method returns users           that are reachable on FB
 Failure/Error: User.should_receive(:where).with( :is_reachable_on_fb   => true,
   <User (class)> received :where with unexpected arguments
     expected: ({:is_reachable_on_fb=>true, "jobs.employer"=>["Apple"], :fb_user_id=>["101", "201"], #<SymbolOperator:0x007f9e28bac958 @field=:fb_user_id, @operator="nin">=>["100", "200"], #<SymbolOperator:0x007f9e28bac778 @field=:fb_user_id, @operator="ne">=>"2", #<SymbolOperator:0x007f9e28bac688 @field=:fb_user_id, @operator="ne">=>"1"})
          got: ({:is_reachable_on_fb=>true, "jobs.employer"=>["Apple"], :fb_user_id=>["101", "201"], #<SymbolOperator:0x007f9e28babcd8 @field=:fb_user_id, @operator="nin">=>["100", "200"], #<SymbolOperator:0x007f9e28bab6c0 @field=:fb_user_id, @operator="ne">=>"2", #<SymbolOperator:0x007f9e28bab148 @field=:fb_user_id, @operator="ne">=>"1"})
 # ./spec/lib/algorithm/helpers/facebook_spec.rb:44:in `block (3 levels) in <module:Helpers>'

From what I can tell, it's just that the SymbolOperators are different. any thoughts on how to avoid this and confirm the right hash is going into the query?

Answer 1

The problem has to do with the way hash equality is calculated in Ruby.

1.9.2-p0 :001 > :something.nin == :something.nin
 => true
1.9.2-p0 :002 > {:something.nin => 'hi'} == {:something.nin => 'hi'}
 => false
1.9.2-p0 :003 > {:something => 'hi'} == {:something => 'hi'}
 => true

For efficiency, I guess Ruby is comparing the hash-codes rather than doing actual == comparisons.

1.9.2-p0 :004 > {:something => 'hi'}.hash
 => 2493047093815769983 
1.9.2-p0 :005 > {:something => 'hi'}.hash
 => 2493047093815769983
1.9.2-p0 :006 > {:something.nin => 'hi'}.hash
 => 2609636779135588412
1.9.2-p0 :007 > {:something.nin => 'hi'}.hash
 => -424522258459261487
1.9.2-p0 :008 > :something.hash
 => 3062293424662012631
1.9.2-p0 :009 > :something.hash
 => 3062293424662012631
1.9.2-p0 :010 > :something.nin.hash
 => -1304763062464413657 
1.9.2-p0 :011 > :something.nin.hash
 => 2727789822935992035

The most permanent fix for your trouble is to define hash for symbol operators and submit a pull request to plucky. There's some discussion here on writing a hash implementation.