add automatic codepage-changing

This code is adapted from the works by Frédéric Van der Essen in
pyxmlescpos.
I had to adapt the code completely in order to make it compatible with
modern unicode-handling

Further changes:
* improve text unittests in CLI and MagicEncode with hypothesis
* add feature force_encoding in order to enable old behaviour
* disable cli_text_test (for now)
* fix charcode(): it does now cooperate with the new structure
* remove redundant variable codepage from class Escpos

test/test_magicencode.py

@@ -1,5 +1,6 @@
 #!/usr/bin/python
-"""tests for panel button function
+#  -*- coding: utf-8 -*-
+"""tests for the magic encode module
 
 :author: `Patrick Kanzler <patrick.kanzler@fablab.fau.de>`_
 :organization: `python-escpos <https://github.com/python-escpos>`_
@@ -12,43 +13,90 @@ from __future__ import division
 from __future__ import print_function
 from __future__ import unicode_literals
 
-from nose.tools import with_setup
+from nose.tools import raises, assert_raises
+from hypothesis import given, example
+import hypothesis.strategies as st
+from escpos.magicencode import MagicEncode
+from escpos.exceptions import CharCodeError, Error
+from escpos.constants import CHARCODE
 
-import escpos.printer as printer
-import os
+@raises(CharCodeError)
+def test_magic_encode_unkown_char_constant_as_startenc():
+    """tests whether MagicEncode raises the proper Exception when an unknown charcode-name is passed as startencoding"""
+    MagicEncode(startencoding="something")
 
-devfile = 'testfile'
+@raises(CharCodeError)
+def test_magic_encode_unkown_char_constant_as_defaultenc():
+    """tests whether MagicEncode raises the proper Exception when an unknown charcode-name is passed as defaultenc."""
+    MagicEncode(defaultencoding="something")
+
+def test_magic_encode_wo_arguments():
+    """tests whether MagicEncode works in the standard configuration"""
+    MagicEncode()
+
+@raises(Error)
+def test_magic_encode_w_non_binary_defaultsymbol():
+    """tests whether MagicEncode catches non-binary defaultsymbols"""
+    MagicEncode(defaultsymbol="non-binary")
+
+@given(symbol=st.binary())
+def test_magic_encode_w_binary_defaultsymbol(symbol):
+    """tests whether MagicEncode works with any binary symbol"""
+    MagicEncode(defaultsymbol=symbol)
+
+@given(st.text())
+@example("カタカナ")
+@example("あいうえお")
+@example("ﾊﾝｶｸｶﾀｶﾅ")
+def test_magic_encode_encode_text_unicode_string(text):
+    """tests whether MagicEncode can accept a unicode string"""
+    me = MagicEncode()
+    me.encode_text(text)
+
+@given(char=st.characters())
+def test_magic_encode_encode_char(char):
+    """tests the encode_char-method of MagicEncode"""
+    me = MagicEncode()
+    me.encode_char(char)
+
+@raises(Error)
+@given(char=st.binary())
+def test_magic_encode_encode_char_binary(char):
+    """tests the encode_char-method of MagicEncode with binary input"""
+    me = MagicEncode()
+    me.encode_char(char)
 
 
-def setup_testfile():
-    """create a testfile as devfile"""
-    fhandle = open(devfile, 'a')
-    try:
-        os.utime(devfile, None)
-    finally:
-        fhandle.close()
+def test_magic_encode_string_with_katakana_and_hiragana():
+    """tests the encode_string-method with katakana and hiragana"""
+    me = MagicEncode()
+    me.encode_str("カタカナ")
+    me.encode_str("あいうえお")
 
+@raises(CharCodeError)
+def test_magic_encode_codepage_sequence_unknown_key():
+    """tests whether MagicEncode.codepage_sequence raises the proper Exception with unknown charcode-names"""
+    MagicEncode.codepage_sequence("something")
 
-def teardown_testfile():
-    """destroy testfile again"""
-    os.remove(devfile)
+@raises(CharCodeError)
+def test_magic_encode_codepage_name_unknown_key():
+    """tests whether MagicEncode.codepage_name raises the proper Exception with unknown charcode-names"""
+    MagicEncode.codepage_name("something")
 
+def test_magic_encode_constants_getter():
+    """tests whether the constants are properly fetched"""
+    for key in CHARCODE:
+        name = CHARCODE[key][1]
+        if name == '':
+            assert_raises(CharCodeError, MagicEncode.codepage_name, key)
+        else:
+            assert name == MagicEncode.codepage_name(key)
+        assert MagicEncode.codepage_sequence(key) == CHARCODE[key][0]
 
-@with_setup(setup_testfile, teardown_testfile)
-def test_function_panel_button_on():
-    """test the panel button function (enabling) by comparing output"""
-    instance = printer.File(devfile=devfile)
-    instance.panel_buttons()
-    instance.flush()
-    with open(devfile, "rb") as f:
-        assert(f.read() == b'\x1B\x63\x35\x00')
-
-
-@with_setup(setup_testfile, teardown_testfile)
-def test_function_panel_button_off():
-    """test the panel button function (disabling) by comparing output"""
-    instance = printer.File(devfile=devfile)
-    instance.panel_buttons(False)
-    instance.flush()
-    with open(devfile, "rb") as f:
-        assert(f.read() == b'\x1B\x63\x35\x01')
+def test_magic_encode_force_encoding():
+    """test whether force_encoding works as expected"""
+    me = MagicEncode()
+    assert me.force_encoding is False
+    me.set_encoding(encoding='KATAKANA', force_encoding=True)
+    assert me.encoding == 'KATAKANA'
+    assert me.force_encoding is True