embedart: fix behaviour on IM unparseable output, add tests

Test all EmbedCoverArtPlugin.check_art_similarity() code paths.

Improve #1241.

beetsplug/embedart.py

@@ -211,6 +211,7 @@ class EmbedCoverArtPlugin(BeetsPlugin):
                 except ValueError:
                     self._log.debug(u'IM output is not a number: {0!r}',
                                     out_str)
+                    return
 
                 self._log.info(u'compare PHASH score is {0}', phash_diff)
                 if phash_diff > compare_threshold:

test/test_embedart.py

@@ -13,6 +13,8 @@
 # included in all copies or substantial portions of the Software.
 
 import os.path
+from mock import Mock, patch
+
 import _common
 from _common import unittest
 from helper import TestHelper, capture_log
@@ -21,6 +23,7 @@ from beets.mediafile import MediaFile
 from beets import config, logging
 from beets.util import syspath
 from beets.util.artresizer import ArtResizer
+from beetsplug.embedart import EmbedCoverArtPlugin
 
 
 def require_artresizer_compare(test):
@@ -110,6 +113,38 @@ class EmbedartCliTest(unittest.TestCase, TestHelper):
                          self.abbey_similarpath))
 
 
+class EmbedartTest(unittest.TestCase):
+    @patch('beetsplug.embedart.subprocess')
+    def test_imagemagick_response(self, mock_subprocess):
+        embed = EmbedCoverArtPlugin()
+        embed.extract = Mock(return_value=True)
+        proc = mock_subprocess.Popen.return_value
+
+        # everything is fine
+        proc.returncode = 0
+        proc.communicate.return_value = "10", "tagada"
+        self.assertTrue(embed.check_art_similarity(None, None, 20))
+        self.assertFalse(embed.check_art_similarity(None, None, 5))
+
+        # small failure
+        proc.returncode = 1
+        proc.communicate.return_value = "tagada", "10"
+        self.assertTrue(embed.check_art_similarity(None, None, 20))
+        self.assertFalse(embed.check_art_similarity(None, None, 5))
+
+        # bigger failure
+        proc.returncode = 2
+        self.assertIsNone(embed.check_art_similarity(None, None, 20))
+
+        # IM result parsing problems
+        proc.returncode = 0
+        proc.communicate.return_value = "foo", "bar"
+        self.assertIsNone(embed.check_art_similarity(None, None, 20))
+
+        proc.returncode = 1
+        self.assertIsNone(embed.check_art_similarity(None, None, 20))
+
+
 def suite():
     return unittest.TestLoader().loadTestsFromName(__name__)