Speed up factories spec by using FactoryDefault

spec/factories_spec.rb

@@ -3,7 +3,7 @@
 require 'spec_helper'
 
 RSpec.describe 'factories' do
-  FactoryBot.factories.each do |factory|
+  shared_examples 'factory' do |factory|
     describe "#{factory.name} factory" do
       it 'does not raise error when built' do
         expect { build(factory.name) }.not_to raise_error
@@ -22,4 +22,32 @@ RSpec.describe 'factories' do
       end
     end
   end
+
+  # FactoryDefault speed up specs by creating associations only once
+  # and reuse them in other factories.
+  #
+  # However, for some factories we cannot use FactoryDefault because the
+  # associations must be unique and cannot be reused.
+  skip_factory_defaults = %i[
+    fork_network_member
+  ].to_set.freeze
+
+  without_fd, with_fd = FactoryBot.factories
+    .partition { |factory| skip_factory_defaults.include?(factory.name) }
+
+  context 'with factory defaults', factory_default: :keep do
+    let_it_be(:namespace) { create_default(:namespace) }
+    let_it_be(:project) { create_default(:project, :repository) }
+    let_it_be(:user) { create_default(:user) }
+
+    with_fd.each do |factory|
+      it_behaves_like 'factory', factory
+    end
+  end
+
+  context 'without factory defaults' do
+    without_fd.each do |factory|
+      it_behaves_like 'factory', factory
+    end
+  end
 end