test add type-check for the qr-printing

src/escpos/escpos.py

@@ -157,7 +157,7 @@ class Escpos(object):
         if not native:
             # Map ESC/POS error correction levels to python 'qrcode' library constant and render to an image
             if model != QR_MODEL_2:
-                raise ValueError("Invalid QR model for qrlib rendering (must be QR_MODEL_2)")
+                raise ValueError("Invalid QR model for python-qrcode rendering (must be QR_MODEL_2)")
             python_qr_ec = {
                 QR_ECLEVEL_H: qrcode.constants.ERROR_CORRECT_H,
                 QR_ECLEVEL_L: qrcode.constants.ERROR_CORRECT_L,
@@ -168,8 +168,7 @@ class Escpos(object):
             qr_code.add_data(content)
             qr_code.make(fit=True)
             qr_img = qr_code.make_image()
-            im = qr_img._img.convert("RGB")
+            im = qr_img.convert("RGB")  # Convert the RGB image in printable image
-            # Convert the RGB image in printable image
             self.image(im)
             return
         # Native 2D code printing

test/test_function_qr_non-native.py

@@ -0,0 +1,32 @@
+#!/usr/bin/python
+#  -*- coding: utf-8 -*-
+"""tests for the non-native part of qr()
+
+:author: `Patrick Kanzler <patrick.kanzler@fablab.fau.de>`_
+:organization: `python-escpos <https://github.com/python-escpos>`_
+:copyright: Copyright (c) 2016 `python-escpos <https://github.com/python-escpos>`_
+:license: GNU GPL v3
+"""
+
+from __future__ import absolute_import
+from __future__ import division
+from __future__ import print_function
+from __future__ import unicode_literals
+
+import mock
+
+from escpos.printer import Dummy
+from PIL import Image
+
+
+@mock.patch('escpos.printer.Dummy.image', spec=Dummy)
+def test_type_of_object_passed_to_image_function(img_function):
+    """
+    Test the type of object that is passed to the image function during non-native qr-printing.
+
+    The type should be PIL.Image
+    """
+    d = Dummy()
+    d.qr("LoremIpsum")
+    args, kwargs = img_function.call_args
+    assert isinstance(args[0], Image.Image)