rspec model attribute change not saving properly
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I am using factory girl to create a model with inventory_count = 3. In my test, I want to test a case for when inventory_count = 0..so here's what I did:

    before(:each) do
      @user = FactoryGirl.create(:user)
      @piece = FactoryGirl.create(:piece)
      @lineup = @user.lineup
    end

    it 'should have status \'Waiting List\' if the piece doesn\'t have available inventory' do
      @piece.available_count = 0
      @lineup.pieces << @piece
      piece_lineup = @lineup.piece_lineups.find_by_piece_id(@piece.id)
      piece_lineup.set_status
      piece_lineup.status.should == 'Waiting List'
    end

I put a debugger after @piece.available_count = 0 and it is = 0, but when it gets down to the next line it switches back to the old value. I tried adding a .save to @piece but it still didn't work. Am i doing something wrong? Should I be creating the new value model in factorygirl instead of trying to do it on the fly?