Refactor first_board method into the Board model

and add proper specs

app/models/board.rb

@@ -12,6 +12,7 @@ class Board < ApplicationRecord
 
   scope :with_associations, -> { preload(:destroyable_lists) }
   scope :order_by_name_asc, -> { order(arel_table[:name].lower.asc) }
+  scope :first_board, -> { where(id: self.order_by_name_asc.limit(1).select(:id)) }
 
   def project_needed?
     !group

app/services/boards/list_service.rb

@@ -20,12 +20,9 @@ module Boards
       parent.boards.order_by_name_asc
     end
 
-    # rubocop: disable CodeReuse/ActiveRecord
     def first_board
-      # We could use just one query but MySQL does not support nested queries using LIMIT
-      boards.where(id: boards.first).reorder(nil)
+      parent.boards.first_board
     end
-    # rubocop: enable CodeReuse/ActiveRecord
 
     def create_board!
       Boards::CreateService.new(parent, current_user).execute

spec/models/board_spec.rb

@@ -3,6 +3,9 @@
 require 'spec_helper'
 
 describe Board do
+  let(:project) { create(:project) }
+  let(:other_project) { create(:project) }
+
   describe 'relationships' do
     it { is_expected.to belong_to(:project) }
     it { is_expected.to have_many(:lists).order(list_type: :asc, position: :asc).dependent(:delete_all) }
@@ -11,4 +14,28 @@ describe Board do
   describe 'validations' do
     it { is_expected.to validate_presence_of(:project) }
   end
+
+  describe '#order_by_name_asc' do
+    let!(:second_board) { create(:board, name: 'Secondary board', project: project) }
+    let!(:first_board)  { create(:board, name: 'First board', project: project) }
+
+    it 'returns in alphabetical order' do
+      expect(project.boards.order_by_name_asc).to eq [first_board, second_board]
+    end
+  end
+
+  describe '#first_board' do
+    let!(:other_board)  { create(:board, name: 'Other board', project: other_project) }
+    let!(:second_board) { create(:board, name: 'Secondary board', project: project) }
+    let!(:first_board)  { create(:board, name: 'First board', project: project) }
+
+    it 'return the first alphabetical board as a relation' do
+      expect(project.boards.first_board).to eq [first_board]
+    end
+
+    # BoardsActions#board expects this behavior
+    it 'raises an error when find is done on a non-existent record' do
+      expect { project.boards.first_board.find(second_board.id) }.to raise_error(ActiveRecord::RecordNotFound)
+    end
+  end
 end

spec/support/shared_examples/services/boards/boards_list_service.rb

@@ -32,7 +32,9 @@ end
 
 shared_examples 'multiple boards list service' do
   let(:service)  { described_class.new(parent, double) }
-  let!(:boards) { create_list(:board, 3, resource_parent: parent) }
+  let!(:board_B) { create(:board, resource_parent: parent, name: 'B-board') }
+  let!(:board_c) { create(:board, resource_parent: parent, name: 'c-board') }
+  let!(:board_a) { create(:board, resource_parent: parent, name: 'a-board') }
 
   describe '#execute' do
     it 'returns all issue boards' do
@@ -40,10 +42,7 @@ shared_examples 'multiple boards list service' do
     end
 
     it 'returns boards ordered by name' do
-      board_names = %w[B-board c-board a-board]
-      boards.each_with_index { |board, i| board.update_column(:name, board_names[i]) }
-
-      expect(service.execute.pluck(:name)).to eq(%w[a-board B-board c-board])
+      expect(service.execute).to eq [board_a, board_B, board_c]
     end
   end
 end