More mypy (#612)

* remove type comment where type is annotated
* move function tests
* remove six from tests
* add none annotations
* add more types
* change mock (so that mypy understands it)

test/test_functions/test_function_panel_button.py

@@ -0,0 +1,25 @@
+#!/usr/bin/python
+"""tests for panel button function
+
+:author: `Patrick Kanzler <dev@pkanzler.de>`_
+:organization: `python-escpos <https://github.com/python-escpos>`_
+:copyright: Copyright (c) 2016 `python-escpos <https://github.com/python-escpos>`_
+:license: MIT
+"""
+
+
+import escpos.printer as printer
+
+
+def test_function_panel_button_on() -> None:
+    """test the panel button function (enabling) by comparing output"""
+    instance = printer.Dummy()
+    instance.panel_buttons()
+    assert instance.output == b"\x1B\x63\x35\x00"
+
+
+def test_function_panel_button_off() -> None:
+    """test the panel button function (disabling) by comparing output"""
+    instance = printer.Dummy()
+    instance.panel_buttons(False)
+    assert instance.output == b"\x1B\x63\x35\x01"