Serializza gli invii SMTP su una coda unica per non far chiudere Aruba.

Co-authored-by: Cursor <cursoragent@cursor.com>

test/services/mailings/smtp_gate_test.rb

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+require "test_helper"
+
+class Mailings::SmtpGateTest < ActiveSupport::TestCase
+  setup do
+    Mailings::SmtpGate.min_gap = 0
+    Mailings::SmtpGate.backoff_base = 0
+    Mailings::SmtpGate.max_attempts = 4
+    Mailings::SmtpGate.reset!
+  end
+
+  teardown do
+    Mailings::SmtpGate.min_gap = 0
+    Mailings::SmtpGate.backoff_base = 0
+    Mailings::SmtpGate.max_attempts = 4
+    Mailings::SmtpGate.reset!
+  end
+
+  test "retries EOFError then succeeds" do
+    hits = 0
+    result = Mailings::SmtpGate.deliver do
+      hits += 1
+      raise EOFError, "end of file reached" if hits < 3
+
+      :sent
+    end
+
+    assert_equal :sent, result
+    assert_equal 3, hits
+  end
+
+  test "gives up after max attempts" do
+    hits = 0
+    error = assert_raises(EOFError) do
+      Mailings::SmtpGate.deliver do
+        hits += 1
+        raise EOFError, "end of file reached"
+      end
+    end
+
+    assert_equal "end of file reached", error.message
+    assert_equal Mailings::SmtpGate.max_attempts, hits
+  end
+
+  test "does not retry permanent SMTP errors" do
+    hits = 0
+    assert_raises(Net::SMTPAuthenticationError) do
+      Mailings::SmtpGate.deliver do
+        hits += 1
+        raise Net::SMTPAuthenticationError, "535 authentication failed"
+      end
+    end
+    assert_equal 1, hits
+  end
+
+  test "serializes concurrent deliveries" do
+    order = Queue.new
+    threads = 2.times.map do |i|
+      Thread.new do
+        Mailings::SmtpGate.deliver do
+          order << i
+          sleep 0.05
+        end
+      end
+    end
+    threads.each(&:join)
+
+    assert_equal 2, order.size
+  end
+end