Add test case to new mblookup functionality

A new test case to check for mblookup's ability to search
for data based on release id is created along with a function
mocks getReleaseMetadata using an existing JSON file.

Signed-off-by: ABCbum <kimlong221002@gmail.com>

whipper/test/test_command_mblookup.py

@@ -4,8 +4,10 @@
 import os
 import pickle
 import unittest
+import json
 
 from whipper.command import mblookup
+from whipper.common.mbngs import _getMetadata
 
 
 class MBLookupTestCase(unittest.TestCase):
@@ -19,6 +21,22 @@ class MBLookupTestCase(unittest.TestCase):
         with open(path, "rb") as p:
             return pickle.load(p)
 
+    @staticmethod
+    def _mock_getReleaseMetadata(release_id):
+        """
+        Mock function for whipper.common.mbngs.getReleaseMetadata.
+
+        :param release_id: MusicBrainz Release ID
+        :type release_id: str
+        :returns: a DiscMetadata object based on the given release_id
+        :rtype: `DiscMetadata`
+        """
+        filename = 'whipper.release.{}.json'.format(release_id)
+        path = os.path.join(os.path.dirname(__file__), filename)
+        with open(path, "rb") as handle:
+            response = json.loads(handle.read().decode('utf-8'))
+        return _getMetadata(response['release'])
+
     def testMissingReleaseType(self):
         """Test that lookup for release without a type set doesn't fail."""
         # Using: Gustafsson, Österberg & Cowle - What's Up? 8 (disc 4)
@@ -28,3 +46,12 @@ class MBLookupTestCase(unittest.TestCase):
         # https://musicbrainz.org/cdtoc/xu338_M8WukSRi0J.KTlDoflB8Y-
         lookup = mblookup.MBLookup([discid], 'whipper mblookup', None)
         lookup.do()
+
+    def testGetDataFromReleaseId(self):
+        """Test that lookup for a release with a specified id."""
+        # Using: The KLF - Space & Chill Out
+        # https://musicbrainz.org/release/c56ff16e-1d81-47de-926f-ba22891bd2bd
+        mblookup.getReleaseMetadata = self._mock_getReleaseMetadata
+        releaseid = 'c56ff16e-1d81-47de-926f-ba22891bd2bd'
+        lookup = mblookup.MBLookup([releaseid], 'whipper mblookup', None)
+        lookup.do()