tests: Show that message encrypt modifies the original one

which is probably not what we want.
If we decide to fix it, the tests' assertions need to be changed.

Closes PYADAPT-99.

tests/test_message.py

@@ -69,3 +69,104 @@ Hi world!
 """.split("\n")
     assert dec_lines[:5] == expected_dec_lines[:5]
     assert dec_lines[7:] == expected_dec_lines[7:]
+
+
+def test_msg_len_changes(create_alice_identity, create_bob_identity):
+    """Test that the original message is modified after encryption.
+
+    Headers are added and therefore the modified unencrypted message length
+    is different to the original.
+    XXX: The original message should be left unchanged.
+         There could be another method previous to `encrypt` that adds the
+         extra headers and modify the subject returning a new message.
+
+    """
+    import pEp
+
+    alice = create_alice_identity
+    bob = create_bob_identity
+
+    msg = pEp.outgoing_message(alice)
+    msg.to = [bob]
+    msg.shortmsg = constants.SUBJECT
+    msg.longmsg = constants.BODY
+    msg_len = len(str(msg))
+    # Encrypt Message
+    msg.encrypt()
+
+    # After encryption, the original message is modified!!
+    # It contains one more header and the alice's public key, if it's the first
+    # msg to bob.
+    # XXX: if/when this is fixed, change the following `!=` to `==`
+    msg_after_encrypt_len = len(str(msg))
+    assert msg.shortmsg != constants.SUBJECT
+    assert msg.longmsg == constants.BODY
+    assert msg_after_encrypt_len != msg_len
+
+
+def test_dec_msg_len(create_alice_identity, create_bob_identity):
+    """
+    Test that the decrypted message length is different from the original.
+
+    Because it adds extra headers.
+
+    """
+    import pEp
+
+    alice = create_alice_identity
+    bob = create_bob_identity
+
+    msg = pEp.outgoing_message(alice)
+    msg.to = [bob]
+    msg.shortmsg = constants.SUBJECT
+    msg.longmsg = constants.BODY
+    msg_len = len(str(msg))
+    # Encrypt Message
+    enc_msg = msg.encrypt()
+
+    # Decrypt message.
+    dec_msg, _key_list, _rating, _r = enc_msg.decrypt()
+    dec_msg_len = len(str(dec_msg))
+
+    assert dec_msg.longmsg.replace("\r", "") == constants.BODY  # msg.longmsg
+    expected_dec_msg = """From: Alice Lovelace <alice@openpgp.example>\r
+To: Bob Babagge <bob@openpgp.example>\r
+Subject: This is a subject\r
+X-pEp-Version: 2.1\r
+X-EncStatus: reliable\r
+X-KeyList: \r
+ EB85BB5FA33A75E15E944E63F231550C4F47E38E,EB85BB5FA33A75E15E944E63F231550C4F47E38E,D1A66E1A23B182C9980F788CFBFCC82A015E7330\r
+MIME-Version: 1.0\r
+Content-Type: text/plain\r
+Content-Transfer-Encoding: 7bit\r
+\r
+Hi world!\r
+"""
+    assert expected_dec_msg == str(dec_msg)
+    # The decrypted message length should then be equal to the original message
+    # minus the extra headers added.
+    dec_lines = str(dec_msg).split("\n")
+    extra_headers_lines = dec_lines[3:7]
+    extra_headers = "\n".join(extra_headers_lines) + "\n"
+    len_extra_headers = len(extra_headers)
+    print("len_extra_headers", len_extra_headers)
+    assert dec_msg_len - len_extra_headers == msg_len
+
+
+def test_null_char_rmed(create_alice_identity, create_bob_identity):
+    """Test that null characters and anything after them is removed."""
+    import pEp
+
+    alice = create_alice_identity
+    bob = create_bob_identity
+
+    msg = pEp.outgoing_message(alice)
+    msg.to = [bob]
+    msg.shortmsg = constants.SUBJECT
+
+    # Message with null chars, potentially for padding.
+    body = "Hi Bob,\n" + "\0" * 255 + "\nBye,\nAlice."
+    msg.longmsg = body
+    # PYADAPT-91: The null characters and anything after them is removed.
+    # If/when this is fixed, change the following assertion.
+    assert msg.longmsg != body