test: add initial tests for Postal::SMTPServer::Client

spec/factories/route_factory.rb

@@ -0,0 +1,14 @@
+# frozen_string_literal: true
+
+FactoryBot.define do
+  factory :route do
+    name { "test" }
+    mode { "Accept" }
+    spam_mode { "Mark" }
+
+    before(:create) do |route|
+      route.server ||= create(:server)
+      route.domain ||= create(:domain, owner: route.server)
+    end
+  end
+end