From b9f52881832c74c004f4a162cda9623d07b69e10 Mon Sep 17 00:00:00 2001
From: Jeffrey Kintscher <websurfer@surf2c.net>
Date: Mon, 27 May 2019 19:19:04 -0700
Subject: [PATCH 1/5] bpo-36520: reset the encoded word offset when starting a
 new line during an email header folding operation

---
 Lib/email/_header_value_parser.py   |  1 +
 Lib/test/test_email/test_message.py | 74 +++++++++++++++++++++++++++++
 2 files changed, 75 insertions(+)

diff --git a/Lib/email/_header_value_parser.py b/Lib/email/_header_value_parser.py
index 649f1539fa02ab..18bab90165489e 100644
--- a/Lib/email/_header_value_parser.py
+++ b/Lib/email/_header_value_parser.py
@@ -2661,6 +2661,7 @@ def _refold_parse_tree(parse_tree, *, policy):
             newline = _steal_trailing_WSP_if_exists(lines)
             if newline or part.startswith_fws():
                 lines.append(newline + tstr)
+                last_ew = None
                 continue
         if not hasattr(part, 'encode'):
             # It's not a terminal, try folding the subparts.
diff --git a/Lib/test/test_email/test_message.py b/Lib/test/test_email/test_message.py
index f3a57df9e9cfd0..cf752ffe264a91 100644
--- a/Lib/test/test_email/test_message.py
+++ b/Lib/test/test_email/test_message.py
@@ -784,6 +784,80 @@ def test_str_defaults_to_utf8(self):
         m['Subject'] = 'unicöde'
         self.assertEqual(str(m), 'Subject: unicöde\n\n')
 
+    def test_folding_with_utf8_encoding_1(self):
+        # issue #36520
+        m = EmailMessage()
+        m['Subject'] = 'Hello Wörld! Hello Wörld! '\
+                       'Hello Wörld! Hello Wörld!Hello Wörld!'
+        self.assertEqual(bytes(m), \
+                         b'Subject: Hello =?utf-8?q?W=C3=B6rld!_Hello_W'\
+                         b'=C3=B6rld!_Hello_W=C3=B6rld!?=\n'\
+                         b' Hello =?utf-8?q?W=C3=B6rld!Hello_W=C3=B6rld!?=\n\n')
+
+
+    def test_folding_with_utf8_encoding_2(self):
+        # issue #36520
+        m = EmailMessage()
+        m['Subject'] = 'Hello Wörld! Hello Wörld! '\
+                       'Hello Wörlds123! Hello Wörld!Hello Wörld!'
+        self.assertEqual(bytes(m), \
+                         b'Subject: Hello =?utf-8?q?W=C3=B6rld!_Hello_W'\
+                         b'=C3=B6rld!_Hello_W=C3=B6rlds123!?=\n'\
+                         b' Hello =?utf-8?q?W=C3=B6rld!Hello_W=C3=B6rld!?=\n\n')
+
+    def test_folding_with_utf8_encoding_3(self):
+        # issue #36520
+        m = EmailMessage()
+        m['Subject'] = 'Hello-Wörld!-Hello-Wörld!-Hello-Wörlds123! '\
+                       'Hello Wörld!Hello Wörld!'
+        self.assertEqual(bytes(m), \
+                         b'Subject: =?utf-8?q?Hello-W=C3=B6rld!-Hello-W'\
+                         b'=C3=B6rld!-Hello-W=C3=B6rlds123!?=\n'\
+                         b' Hello =?utf-8?q?W=C3=B6rld!Hello_W=C3=B6rld!?=\n\n')
+
+    def test_folding_with_utf8_encoding_4(self):
+        # issue #36520
+        m = EmailMessage()
+        m['Subject'] = 'Hello-Wörld!-Hello-Wörld!-Hello-Wörlds123!-Hello'\
+                       ' Wörld!Hello Wörld!'
+        self.assertEqual(bytes(m), \
+                         b'Subject: =?utf-8?q?Hello-W=C3=B6rld!-Hello-W'\
+                         b'=C3=B6rld!-Hello-W=C3=B6rlds123!?=\n'\
+                         b' =?utf-8?q?-Hello_W=C3=B6rld!Hello_W=C3=B6rld!?=\n\n')
+
+    def test_folding_with_utf8_encoding_5(self):
+        # issue #36520
+        m = EmailMessage()
+        m['Subject'] = '123456789 123456789 123456789 123456789 123456789'\
+                       ' 123456789 123456789 Hello Wörld!'
+        self.assertEqual(bytes(m), \
+                         b'Subject: 123456789 123456789 123456789 123456789'\
+                         b' 123456789 123456789 123456789\n'\
+                         b' Hello =?utf-8?q?W=C3=B6rld!?=\n\n')
+
+    def test_folding_with_utf8_encoding_6(self):
+        # issue #36520
+        m = EmailMessage()
+        m['Subject'] = '123456789 123456789 123456789 123456789 Hello Wörld!'\
+                       ' 123456789 123456789 123456789 123456789 123456789'\
+                       ' 123456789'
+        self.assertEqual(bytes(m), \
+                         b'Subject: 123456789 123456789 123456789 123456789'\
+                         b' Hello =?utf-8?q?W=C3=B6rld!?=\n 123456789 '\
+                         b'123456789 123456789 123456789 123456789 '\
+                         b'123456789\n\n')
+
+    def test_folding_with_utf8_encoding_7(self):
+        # issue #36520
+        m = EmailMessage()
+        m['Subject'] = '123456789 123456789 Hello Wörld! Hello Wörld! '\
+                       '123456789-123456789 123456789 Hello Wörld! 123456789'\
+                       ' 123456789'
+        self.assertEqual(bytes(m), \
+                         b'Subject: 123456789 123456789 Hello =?utf-8?q?'\
+                         b'W=C3=B6rld!_Hello_W=C3=B6rld!?=\n'\
+                         b' 123456789-123456789 123456789 Hello '\
+                         b'=?utf-8?q?W=C3=B6rld!?= 123456789\n 123456789\n\n')
 
 class TestMIMEPart(TestEmailMessageBase, TestEmailBase):
     # Doing the full test run here may seem a bit redundant, since the two

From d989f75a2b53cfe1b96c6f118da848d757e91ddf Mon Sep 17 00:00:00 2001
From: "blurb-it[bot]" <blurb-it[bot]@users.noreply.github.com>
Date: Tue, 28 May 2019 02:37:01 +0000
Subject: [PATCH 2/5] =?UTF-8?q?=F0=9F=93=9C=F0=9F=A4=96=20Added=20by=20blu?=
 =?UTF-8?q?rb=5Fit.?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .../NEWS.d/next/Library/2019-05-28-02-37-00.bpo-36520.W4tday.rst | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 Misc/NEWS.d/next/Library/2019-05-28-02-37-00.bpo-36520.W4tday.rst

diff --git a/Misc/NEWS.d/next/Library/2019-05-28-02-37-00.bpo-36520.W4tday.rst b/Misc/NEWS.d/next/Library/2019-05-28-02-37-00.bpo-36520.W4tday.rst
new file mode 100644
index 00000000000000..28eee259682295
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2019-05-28-02-37-00.bpo-36520.W4tday.rst
@@ -0,0 +1 @@
+Lengthy email headers with UTF-8 characters are now properly encoded when they are folded.
\ No newline at end of file

From d4e969ba8a0c156e84ec2a297d7d98b3310f4cbb Mon Sep 17 00:00:00 2001
From: Jeffrey Kintscher <websurfer@surf2c.net>
Date: Wed, 29 May 2019 16:46:31 -0700
Subject: [PATCH 3/5] bpo-36520: add an additional test case, and provide
 descriptive comments for the test_folding_with_utf8_encoding_* tests

---
 Lib/test/test_email/test_message.py           | 57 +++++++++++++++++++
 .../2019-05-28-02-37-00.bpo-36520.W4tday.rst  |  2 +-
 2 files changed, 58 insertions(+), 1 deletion(-)

diff --git a/Lib/test/test_email/test_message.py b/Lib/test/test_email/test_message.py
index cf752ffe264a91..b8d35bc827eac8 100644
--- a/Lib/test/test_email/test_message.py
+++ b/Lib/test/test_email/test_message.py
@@ -786,6 +786,12 @@ def test_str_defaults_to_utf8(self):
 
     def test_folding_with_utf8_encoding_1(self):
         # issue #36520
+        #
+        # Fold a line that contains UTF-8 words before
+        # and after the whitespace fold point, where the
+        # line length limit is reached within an ASCII
+        # word.
+
         m = EmailMessage()
         m['Subject'] = 'Hello Wörld! Hello Wörld! '\
                        'Hello Wörld! Hello Wörld!Hello Wörld!'
@@ -797,6 +803,12 @@ def test_folding_with_utf8_encoding_1(self):
 
     def test_folding_with_utf8_encoding_2(self):
         # issue #36520
+        #
+        # Fold a line that contains UTF-8 words before
+        # and after the whitespace fold point, where the
+        # line length limit is reached at the end of an
+        # encoded word.
+
         m = EmailMessage()
         m['Subject'] = 'Hello Wörld! Hello Wörld! '\
                        'Hello Wörlds123! Hello Wörld!Hello Wörld!'
@@ -807,6 +819,12 @@ def test_folding_with_utf8_encoding_2(self):
 
     def test_folding_with_utf8_encoding_3(self):
         # issue #36520
+        #
+        # Fold a line that contains UTF-8 words before
+        # and after the whitespace fold point, where the
+        # line length limit is reached at the end of the
+        # first word.
+
         m = EmailMessage()
         m['Subject'] = 'Hello-Wörld!-Hello-Wörld!-Hello-Wörlds123! '\
                        'Hello Wörld!Hello Wörld!'
@@ -817,6 +835,12 @@ def test_folding_with_utf8_encoding_3(self):
 
     def test_folding_with_utf8_encoding_4(self):
         # issue #36520
+        #
+        # Fold a line that contains UTF-8 words before
+        # and after the fold point, where the first
+        # word is UTF-8 and the fold point is within
+        # the word.
+
         m = EmailMessage()
         m['Subject'] = 'Hello-Wörld!-Hello-Wörld!-Hello-Wörlds123!-Hello'\
                        ' Wörld!Hello Wörld!'
@@ -827,6 +851,10 @@ def test_folding_with_utf8_encoding_4(self):
 
     def test_folding_with_utf8_encoding_5(self):
         # issue #36520
+        #
+        # Fold a line that contains a UTF-8 word after
+        # the fold point.
+
         m = EmailMessage()
         m['Subject'] = '123456789 123456789 123456789 123456789 123456789'\
                        ' 123456789 123456789 Hello Wörld!'
@@ -837,6 +865,10 @@ def test_folding_with_utf8_encoding_5(self):
 
     def test_folding_with_utf8_encoding_6(self):
         # issue #36520
+        #
+        # Fold a line that contains a UTF-8 word before
+        # the fold point and ASCII words after
+
         m = EmailMessage()
         m['Subject'] = '123456789 123456789 123456789 123456789 Hello Wörld!'\
                        ' 123456789 123456789 123456789 123456789 123456789'\
@@ -849,6 +881,11 @@ def test_folding_with_utf8_encoding_6(self):
 
     def test_folding_with_utf8_encoding_7(self):
         # issue #36520
+        #
+        # Fold a line twice that contains UTF-8 words before
+        # and after the first fold point, and ASCII words
+        # after the second fold point.
+
         m = EmailMessage()
         m['Subject'] = '123456789 123456789 Hello Wörld! Hello Wörld! '\
                        '123456789-123456789 123456789 Hello Wörld! 123456789'\
@@ -859,6 +896,26 @@ def test_folding_with_utf8_encoding_7(self):
                          b' 123456789-123456789 123456789 Hello '\
                          b'=?utf-8?q?W=C3=B6rld!?= 123456789\n 123456789\n\n')
 
+    def test_folding_with_utf8_encoding_8(self):
+        # issue #36520
+        #
+        # Fold a line twice that contains UTF-8 words before
+        # the first fold point, and ASCII words after the
+        # first fold point, and UTF-8 words after the second
+        # fold point.
+        
+        m = EmailMessage()
+        m['Subject'] = '123456789 123456789 Hello Wörld! Hello Wörld! '\
+                       '123456789 123456789 123456789 123456789 123456789 '\
+                       '123456789-123456789 123456789 Hello Wörld! 123456789'\
+                       ' 123456789'
+        self.assertEqual(bytes(m), \
+                         b'Subject: 123456789 123456789 Hello '\
+                         b'=?utf-8?q?W=C3=B6rld!_Hello_W=C3=B6rld!?=\n 123456789 '\
+                         b'123456789 123456789 123456789 123456789 '\
+                         b'123456789-123456789\n 123456789 Hello '\
+                         b'=?utf-8?q?W=C3=B6rld!?= 123456789 123456789\n\n')
+
 class TestMIMEPart(TestEmailMessageBase, TestEmailBase):
     # Doing the full test run here may seem a bit redundant, since the two
     # classes are almost identical.  But what if they drift apart?  So we do
diff --git a/Misc/NEWS.d/next/Library/2019-05-28-02-37-00.bpo-36520.W4tday.rst b/Misc/NEWS.d/next/Library/2019-05-28-02-37-00.bpo-36520.W4tday.rst
index 28eee259682295..8171bfe9e2df12 100644
--- a/Misc/NEWS.d/next/Library/2019-05-28-02-37-00.bpo-36520.W4tday.rst
+++ b/Misc/NEWS.d/next/Library/2019-05-28-02-37-00.bpo-36520.W4tday.rst
@@ -1 +1 @@
-Lengthy email headers with UTF-8 characters are now properly encoded when they are folded.
\ No newline at end of file
+Lengthy email headers with UTF-8 characters are now properly encoded when they are folded. Patch by Jeffrey Kintscher.

From a34251995d2d80e8c164a25d5cb8eca95304c977 Mon Sep 17 00:00:00 2001
From: Jeffrey Kintscher <websurfer@surf2c.net>
Date: Wed, 29 May 2019 17:17:49 -0700
Subject: [PATCH 4/5] bpo-36520: fix whitespace issue

---
 Lib/test/test_email/test_message.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Lib/test/test_email/test_message.py b/Lib/test/test_email/test_message.py
index b8d35bc827eac8..b2d5541aa5ff8f 100644
--- a/Lib/test/test_email/test_message.py
+++ b/Lib/test/test_email/test_message.py
@@ -903,7 +903,7 @@ def test_folding_with_utf8_encoding_8(self):
         # the first fold point, and ASCII words after the
         # first fold point, and UTF-8 words after the second
         # fold point.
-        
+
         m = EmailMessage()
         m['Subject'] = '123456789 123456789 Hello Wörld! Hello Wörld! '\
                        '123456789 123456789 123456789 123456789 123456789 '\

From 8133eeb2cb7a7b3822cb5d9585a08a1b7a77ca1a Mon Sep 17 00:00:00 2001
From: Jeffrey Kintscher <websurfer@surf2c.net>
Date: Tue, 4 Jun 2019 14:57:49 -0700
Subject: [PATCH 5/5] bpo-36520: changes per reviewer request -- remove
 extraneous backslashes; add whitespace between terminating quotes and
 line-continuation backslashes; use "bpo-" instead of "issue #" in comments

---
 Lib/test/test_email/test_message.py | 94 ++++++++++++++---------------
 1 file changed, 47 insertions(+), 47 deletions(-)

diff --git a/Lib/test/test_email/test_message.py b/Lib/test/test_email/test_message.py
index b2d5541aa5ff8f..5dc46e1b812c5d 100644
--- a/Lib/test/test_email/test_message.py
+++ b/Lib/test/test_email/test_message.py
@@ -785,7 +785,7 @@ def test_str_defaults_to_utf8(self):
         self.assertEqual(str(m), 'Subject: unicöde\n\n')
 
     def test_folding_with_utf8_encoding_1(self):
-        # issue #36520
+        # bpo-36520
         #
         # Fold a line that contains UTF-8 words before
         # and after the whitespace fold point, where the
@@ -793,16 +793,16 @@ def test_folding_with_utf8_encoding_1(self):
         # word.
 
         m = EmailMessage()
-        m['Subject'] = 'Hello Wörld! Hello Wörld! '\
+        m['Subject'] = 'Hello Wörld! Hello Wörld! '            \
                        'Hello Wörld! Hello Wörld!Hello Wörld!'
-        self.assertEqual(bytes(m), \
-                         b'Subject: Hello =?utf-8?q?W=C3=B6rld!_Hello_W'\
-                         b'=C3=B6rld!_Hello_W=C3=B6rld!?=\n'\
+        self.assertEqual(bytes(m),
+                         b'Subject: Hello =?utf-8?q?W=C3=B6rld!_Hello_W'
+                         b'=C3=B6rld!_Hello_W=C3=B6rld!?=\n'
                          b' Hello =?utf-8?q?W=C3=B6rld!Hello_W=C3=B6rld!?=\n\n')
 
 
     def test_folding_with_utf8_encoding_2(self):
-        # issue #36520
+        # bpo-36520
         #
         # Fold a line that contains UTF-8 words before
         # and after the whitespace fold point, where the
@@ -810,15 +810,15 @@ def test_folding_with_utf8_encoding_2(self):
         # encoded word.
 
         m = EmailMessage()
-        m['Subject'] = 'Hello Wörld! Hello Wörld! '\
+        m['Subject'] = 'Hello Wörld! Hello Wörld! '                \
                        'Hello Wörlds123! Hello Wörld!Hello Wörld!'
-        self.assertEqual(bytes(m), \
-                         b'Subject: Hello =?utf-8?q?W=C3=B6rld!_Hello_W'\
-                         b'=C3=B6rld!_Hello_W=C3=B6rlds123!?=\n'\
+        self.assertEqual(bytes(m),
+                         b'Subject: Hello =?utf-8?q?W=C3=B6rld!_Hello_W'
+                         b'=C3=B6rld!_Hello_W=C3=B6rlds123!?=\n'
                          b' Hello =?utf-8?q?W=C3=B6rld!Hello_W=C3=B6rld!?=\n\n')
 
     def test_folding_with_utf8_encoding_3(self):
-        # issue #36520
+        # bpo-36520
         #
         # Fold a line that contains UTF-8 words before
         # and after the whitespace fold point, where the
@@ -826,15 +826,15 @@ def test_folding_with_utf8_encoding_3(self):
         # first word.
 
         m = EmailMessage()
-        m['Subject'] = 'Hello-Wörld!-Hello-Wörld!-Hello-Wörlds123! '\
+        m['Subject'] = 'Hello-Wörld!-Hello-Wörld!-Hello-Wörlds123! ' \
                        'Hello Wörld!Hello Wörld!'
         self.assertEqual(bytes(m), \
-                         b'Subject: =?utf-8?q?Hello-W=C3=B6rld!-Hello-W'\
-                         b'=C3=B6rld!-Hello-W=C3=B6rlds123!?=\n'\
+                         b'Subject: =?utf-8?q?Hello-W=C3=B6rld!-Hello-W'
+                         b'=C3=B6rld!-Hello-W=C3=B6rlds123!?=\n'
                          b' Hello =?utf-8?q?W=C3=B6rld!Hello_W=C3=B6rld!?=\n\n')
 
     def test_folding_with_utf8_encoding_4(self):
-        # issue #36520
+        # bpo-36520
         #
         # Fold a line that contains UTF-8 words before
         # and after the fold point, where the first
@@ -842,62 +842,62 @@ def test_folding_with_utf8_encoding_4(self):
         # the word.
 
         m = EmailMessage()
-        m['Subject'] = 'Hello-Wörld!-Hello-Wörld!-Hello-Wörlds123!-Hello'\
+        m['Subject'] = 'Hello-Wörld!-Hello-Wörld!-Hello-Wörlds123!-Hello' \
                        ' Wörld!Hello Wörld!'
-        self.assertEqual(bytes(m), \
-                         b'Subject: =?utf-8?q?Hello-W=C3=B6rld!-Hello-W'\
-                         b'=C3=B6rld!-Hello-W=C3=B6rlds123!?=\n'\
+        self.assertEqual(bytes(m),
+                         b'Subject: =?utf-8?q?Hello-W=C3=B6rld!-Hello-W'
+                         b'=C3=B6rld!-Hello-W=C3=B6rlds123!?=\n'
                          b' =?utf-8?q?-Hello_W=C3=B6rld!Hello_W=C3=B6rld!?=\n\n')
 
     def test_folding_with_utf8_encoding_5(self):
-        # issue #36520
+        # bpo-36520
         #
         # Fold a line that contains a UTF-8 word after
         # the fold point.
 
         m = EmailMessage()
-        m['Subject'] = '123456789 123456789 123456789 123456789 123456789'\
+        m['Subject'] = '123456789 123456789 123456789 123456789 123456789' \
                        ' 123456789 123456789 Hello Wörld!'
-        self.assertEqual(bytes(m), \
-                         b'Subject: 123456789 123456789 123456789 123456789'\
-                         b' 123456789 123456789 123456789\n'\
+        self.assertEqual(bytes(m),
+                         b'Subject: 123456789 123456789 123456789 123456789'
+                         b' 123456789 123456789 123456789\n'
                          b' Hello =?utf-8?q?W=C3=B6rld!?=\n\n')
 
     def test_folding_with_utf8_encoding_6(self):
-        # issue #36520
+        # bpo-36520
         #
         # Fold a line that contains a UTF-8 word before
         # the fold point and ASCII words after
 
         m = EmailMessage()
-        m['Subject'] = '123456789 123456789 123456789 123456789 Hello Wörld!'\
-                       ' 123456789 123456789 123456789 123456789 123456789'\
+        m['Subject'] = '123456789 123456789 123456789 123456789 Hello Wörld!' \
+                       ' 123456789 123456789 123456789 123456789 123456789'   \
                        ' 123456789'
-        self.assertEqual(bytes(m), \
-                         b'Subject: 123456789 123456789 123456789 123456789'\
-                         b' Hello =?utf-8?q?W=C3=B6rld!?=\n 123456789 '\
-                         b'123456789 123456789 123456789 123456789 '\
+        self.assertEqual(bytes(m),
+                         b'Subject: 123456789 123456789 123456789 123456789'
+                         b' Hello =?utf-8?q?W=C3=B6rld!?=\n 123456789 '
+                         b'123456789 123456789 123456789 123456789 '
                          b'123456789\n\n')
 
     def test_folding_with_utf8_encoding_7(self):
-        # issue #36520
+        # bpo-36520
         #
         # Fold a line twice that contains UTF-8 words before
         # and after the first fold point, and ASCII words
         # after the second fold point.
 
         m = EmailMessage()
-        m['Subject'] = '123456789 123456789 Hello Wörld! Hello Wörld! '\
-                       '123456789-123456789 123456789 Hello Wörld! 123456789'\
+        m['Subject'] = '123456789 123456789 Hello Wörld! Hello Wörld! '       \
+                       '123456789-123456789 123456789 Hello Wörld! 123456789' \
                        ' 123456789'
-        self.assertEqual(bytes(m), \
-                         b'Subject: 123456789 123456789 Hello =?utf-8?q?'\
-                         b'W=C3=B6rld!_Hello_W=C3=B6rld!?=\n'\
-                         b' 123456789-123456789 123456789 Hello '\
+        self.assertEqual(bytes(m),
+                         b'Subject: 123456789 123456789 Hello =?utf-8?q?'
+                         b'W=C3=B6rld!_Hello_W=C3=B6rld!?=\n'
+                         b' 123456789-123456789 123456789 Hello '
                          b'=?utf-8?q?W=C3=B6rld!?= 123456789\n 123456789\n\n')
 
     def test_folding_with_utf8_encoding_8(self):
-        # issue #36520
+        # bpo-36520
         #
         # Fold a line twice that contains UTF-8 words before
         # the first fold point, and ASCII words after the
@@ -905,15 +905,15 @@ def test_folding_with_utf8_encoding_8(self):
         # fold point.
 
         m = EmailMessage()
-        m['Subject'] = '123456789 123456789 Hello Wörld! Hello Wörld! '\
-                       '123456789 123456789 123456789 123456789 123456789 '\
-                       '123456789-123456789 123456789 Hello Wörld! 123456789'\
+        m['Subject'] = '123456789 123456789 Hello Wörld! Hello Wörld! '       \
+                       '123456789 123456789 123456789 123456789 123456789 '   \
+                       '123456789-123456789 123456789 Hello Wörld! 123456789' \
                        ' 123456789'
-        self.assertEqual(bytes(m), \
-                         b'Subject: 123456789 123456789 Hello '\
-                         b'=?utf-8?q?W=C3=B6rld!_Hello_W=C3=B6rld!?=\n 123456789 '\
-                         b'123456789 123456789 123456789 123456789 '\
-                         b'123456789-123456789\n 123456789 Hello '\
+        self.assertEqual(bytes(m),
+                         b'Subject: 123456789 123456789 Hello '
+                         b'=?utf-8?q?W=C3=B6rld!_Hello_W=C3=B6rld!?=\n 123456789 '
+                         b'123456789 123456789 123456789 123456789 '
+                         b'123456789-123456789\n 123456789 Hello '
                          b'=?utf-8?q?W=C3=B6rld!?= 123456789 123456789\n\n')
 
 class TestMIMEPart(TestEmailMessageBase, TestEmailBase):