Refactor outer functions within classes.

Use mypy strict optional checks and fix them.
Use better comparison for compatiblity output.
Add initial socket tests.

test/mypy-py2.sh

@@ -7,4 +7,4 @@ if [ $? -ne 0 ]; then
 fi
 _htmldir="${_cdir}/../html/mypy-py2"
 mkdir -p "${_htmldir}"
-mypy --python-version 2.7 --config-file "${_cdir}/mypy.ini" --html-report "${_htmldir}" "${_cdir}/../ssh-audit.py"
+mypy --python-version 2.7 --strict-optional --config-file "${_cdir}/mypy.ini" --html-report "${_htmldir}" "${_cdir}/../ssh-audit.py"

test/mypy-py3.sh

@@ -7,4 +7,4 @@ if [ $? -ne 0 ]; then
 fi
 _htmldir="${_cdir}/../html/mypy-py3"
 mkdir -p "${_htmldir}"
-mypy --python-version 3.5 --config-file "${_cdir}/mypy.ini" --html-report "${_htmldir}" "${_cdir}/../ssh-audit.py"
+mypy --python-version 3.5 --strict-optional --config-file "${_cdir}/mypy.ini" --html-report "${_htmldir}" "${_cdir}/../ssh-audit.py"

test/test_socket.py

@@ -0,0 +1,41 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+import socket
+import pytest
+
+
+# pylint: disable=attribute-defined-outside-init
+class TestSocket(object):
+	@pytest.fixture(autouse=True)
+	def init(self, ssh_audit):
+		self.ssh = ssh_audit.SSH
+	
+	def test_invalid_host(self, virtual_socket):
+		with pytest.raises(ValueError):
+			s = self.ssh.Socket(None, 22)
+	
+	def test_invalid_port(self, virtual_socket):
+		with pytest.raises(ValueError):
+			s = self.ssh.Socket('localhost', 'abc')
+		with pytest.raises(ValueError):
+			s = self.ssh.Socket('localhost', -1)
+		with pytest.raises(ValueError):
+			s = self.ssh.Socket('localhost', 0)
+		with pytest.raises(ValueError):
+			s = self.ssh.Socket('localhost', 65536)
+	
+	def test_not_connected_socket(self, virtual_socket):
+		sock = self.ssh.Socket('localhost', 22)
+		banner, header, err = sock.get_banner()
+		assert banner is None
+		assert len(header) == 0
+		assert err == 'not connected'
+		s, e = sock.recv()
+		assert s == -1
+		assert e == 'not connected'
+		s, e = sock.send('nothing')
+		assert s == -1
+		assert e == 'not connected'
+		s, e = sock.send_packet()
+		assert s == -1
+		assert e == 'not connected'