Allow Boards::ListService to find a single board

app/services/boards/list_service.rb

@@ -5,13 +5,7 @@ module Boards
     def execute(create_default_board: true)
       create_board! if create_default_board && parent.boards.empty?
 
-      if parent.multiple_issue_boards_available?
-        boards
-      else
-        # When multiple issue boards are not available
-        # a user is only allowed to view the default shown board
-        first_board
-      end
+      find_boards
     end
 
     private
@@ -27,5 +21,18 @@ module Boards
     def create_board!
       Boards::CreateService.new(parent, current_user).execute
     end
+
+    def find_boards
+      found =
+        if parent.multiple_issue_boards_available?
+          boards
+        else
+          # When multiple issue boards are not available
+          # a user is only allowed to view the default shown board
+          first_board
+        end
+
+      params[:board_id].present? ? [found.find(params[:board_id])] : found
+    end
   end
 end

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

@@ -50,5 +50,20 @@ RSpec.shared_examples 'multiple boards list service' do
     it 'returns boards ordered by name' do
       expect(service.execute).to eq [board_a, board_B, board_c]
     end
+
+    context 'when wanting a specific board' do
+      it 'returns board specified by id' do
+        service = described_class.new(parent, double, board_id: board_c.id)
+
+        expect(service.execute).to eq [board_c]
+      end
+
+      it 'raises exception when board is not found' do
+        outside_board = create(:board, resource_parent: create(:project), name: 'outside board')
+        service = described_class.new(parent, double, board_id: outside_board.id)
+
+        expect { service.execute }.to raise_exception(ActiveRecord::RecordNotFound)
+      end
+    end
   end
 end