test: add test for dkim header generation

spec/examples/dkim_signing/email.msg

@@ -0,0 +1,37 @@
+domain: adamtest.viaduct.io
+time: 1626973299
+dkim_identifier: postal-hg3YOm
+private_key: |
+  -----BEGIN RSA PRIVATE KEY-----
+  MIICWwIBAAKBgQDVebmUOjOp4WhVFdwXiHE0sIN0/pxG1lXka8b7wCcKXo7c0Bcp
+  2t77AUP3Lr3HOdY1OKYU8UzbLR5dahvwoodEo2QgFB6wxP9FF/koip+YdmWSscZI
+  9xMZBPcJYfMa3MtC2JC0aDHaKRTSlehg9/T77dJEL11pePdKJtyWZsxNlwIDAQAB
+  AoGAYBdWzb4VG1b3W7VnSMCGFK2Pvs4NEmXQa+2HuDKaYDSIIiUZCCIZVOsQ6OcF
+  TfRe074YJD0p107L6EinIv5F3HEp6pMT3gzo057mPabskohUXbDXcX3kq+0EDMYx
+  1HmlyRvWb6CI79hZrJavF5vOPZxSnM123Y7L0wc1WEKPxSECQQDq3iH/JNPmwDBS
+  DeY6KR6+q7hKGmvcfWfiPQh+PYaekE6635+au3qE8sp+xwiQDbsq9ywwj8J/8Lzt
+  FnvSi+/DAkEA6K7Zw8OHZpq3QwEfazTSm2A+iciD88ISl4g+71Cu6AVnaip5KdxI
+  yiEWE3z/3Y99NPyL1AGouohBCqHD3qOBnQJAWumRD0oaG//YtGpc67ZvCC9ALq77
+  gWWpiJFHcFYwfcAuOXfGOAbJ7hxs9ZXlYp1uDbuPh1yeVRfCiaNiWqWAMQJAJnuc
+  qoLxJugZvSw3XQy8dFQjo7gVEsCbQJKZDg2DD/6szuM9bM3w//Ue6JQ44RT1OUk3
+  exXXKRqV30NH2M+kBQJAJmVIeroVONXhsw/O18dtM4zSbr4glPKBHz73MVO3WK5v
+  ZM1TKedFNOujh8cEyYsoQRaIbGvTcnSMQfMYw7Inhw==
+  -----END RSA PRIVATE KEY-----
+headers: date:from:to:message-id:subject:mime-version:content-type:content-transfer-encoding
+bh: mvuu3b9qEfdaZCSaVxLvRSqKbMB5YN4qxRCRw5FtvuE=
+b: UZgYjsed5ngc9+U/80FMsHIWLTaxj/OBc5r1l9sKbOIz0rmdRnp+X/YCFq16/AY8PWsrJh+/FgIs/zR9hWn+F2iz7dSfvnTE70zKy1q+JIyNh5cw1HegnIgZqG5S6IdliiwaiCFlxMbya790z//jUh5pJdOcm2QuA+fDOGdfU3k=
+---
+DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=adamtest.viaduct.io; s=postal-hg3YOm; t=1626973299; bh=mvuu3b9qEfdaZCSaVxLvRSqKbMB5YN4qxRCRw5FtvuE=; h=date:from:to:message-id:subject:mime-version:content-type:content-transfer-encoding; b=UZgYjsed5ngc9+U/80FMsHIWLTaxj/OBc5r1l9sKbOIz0rmdRnp+X/YCFq16/AY8PWsrJh+/FgIs/zR9hWn+F2iz7dSfvnTE70zKy1q+JIyNh5cw1HegnIgZqG5S6IdliiwaiCFlxMbya790z//jUh5pJdOcm2QuA+fDOGdfU3k=
+X-Postal-MsgID: mPVbUwFRWZcU
+Received: from web-ui (10.210.10.54 [10.210.10.54]) by Postal with HTTP; Thu, 22 Jul 2021 17:01:39 +0000
+Date: Thu, 22 Jul 2021 18:01:39 +0100
+From: test@adamtest.viaduct.io
+To: JfkFM0Sy6bTz1N@dkimvalidator.com
+Message-ID: <d996f20d-c0c5-46d5-ba22-3bac0d859142@rp.adampostal.viaduct.io>
+Subject: Test Message at July 22, 2021 13:01
+Mime-Version: 1.0
+Content-Type: text/plain;
+ charset=UTF-8
+Content-Transfer-Encoding: 7bit
+
+This is a message to test the delivery of messages through Postal.

spec/lib/postal/dkim_header_spec.rb

@@ -0,0 +1,35 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+describe Postal::DKIMHeader do
+
+  examples = Rails.root.join('spec/examples/dkim_signing/*.msg')
+  Dir[examples].each do |path|
+    contents = File.read(path)
+    frontmatter, email = contents.split(/^---\n/m, 2)
+    frontmatter = YAML.load(frontmatter)
+    email.strip
+    it "works with #{path.split('/').first}" do
+      mocked_time = Time.at(frontmatter['time'].to_i)
+      allow(Time).to receive(:now).and_return(mocked_time)
+
+      domain = instance_double('Domain')
+      allow(domain).to receive(:dkim_status).and_return('OK')
+      allow(domain).to receive(:name).and_return(frontmatter['domain'])
+      allow(domain).to receive(:dkim_key).and_return(OpenSSL::PKey::RSA.new(frontmatter['private_key']))
+      allow(domain).to receive(:dkim_identifier).and_return(frontmatter['dkim_identifier'])
+
+      expectation = "DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; "  \
+                    "d=#{frontmatter['domain']}; s=#{frontmatter['dkim_identifier']}; t=#{mocked_time.to_i}; " \
+                    "bh=#{frontmatter['bh']}; "\
+                    "h=#{frontmatter['headers']}; " \
+                    "b=#{frontmatter['b']}"
+
+      header = described_class.new(domain, email)
+
+      expect(header.dkim_header).to eq expectation
+    end
+  end
+
+end