Add a test for our fix

tests/test_future/test_email_generation.py

@@ -0,0 +1,30 @@
+# -*- coding: utf-8 -*-
+"""Tests for email generation."""
+
+from __future__ import unicode_literals
+
+from future.backports.email.mime.multipart import MIMEMultipart
+from future.backports.email.mime.text import MIMEText
+from future.backports.email.utils import formatdate
+from future.tests.base import unittest
+
+
+class EmailGenerationTests(unittest.TestCase):
+    def test_email_custom_header_can_contain_unicode(self):
+        msg = MIMEMultipart()
+        alternative = MIMEMultipart('alternative')
+        alternative.attach(MIMEText('Plain content with Únicødê', _subtype='plain', _charset='utf-8'))
+        alternative.attach(MIMEText('HTML content with Únicødê', _subtype='html', _charset='utf-8'))
+        msg.attach(alternative)
+
+        msg['Subject'] = 'Subject with Únicødê'
+        msg['From'] = 'sender@test.com'
+        msg['To'] = 'recipient@test.com'
+        msg['Date'] = formatdate(None, localtime=True)
+        msg['Message-ID'] = 'anIdWithÚnicødêForThisEmail'
+
+        msg_lines = msg.as_string().split('\n')
+        self.assertEqual(msg_lines[2], 'Subject: =?utf-8?b?U3ViamVjdCB3aXRoIMOabmljw7hkw6o=?=')
+        self.assertEqual(msg_lines[6], 'Message-ID: =?utf-8?b?YW5JZFdpdGjDmm5pY8O4ZMOqRm9yVGhpc0VtYWls?=')
+        self.assertEqual(msg_lines[17], 'UGxhaW4gY29udGVudCB3aXRoIMOabmljw7hkw6o=')
+        self.assertEqual(msg_lines[24], 'SFRNTCBjb250ZW50IHdpdGggw5puaWPDuGTDqg==')