Refactor TestCase files into python modules

Convert all TestCase files into standard python modules to be run and
discovered by unittest.

tests/test_signatures.py

@@ -0,0 +1,44 @@
+#!/usr/bin/env python3
+
+import hashlib
+import os
+import unittest
+from tempfile import TemporaryDirectory
+
+from .testcommon import TmpCwd
+from fdroidserver import common, signatures
+
+basedir = os.path.dirname(__file__)
+
+
+class SignaturesTest(unittest.TestCase):
+    def setUp(self):
+        common.config = None
+        config = common.read_config()
+        config['jarsigner'] = common.find_sdk_tools_cmd('jarsigner')
+        config['verbose'] = True
+        common.config = config
+
+    def test_main(self):
+
+        class OptionsFixture:
+            APK = [os.path.join(basedir, 'repo', 'com.politedroid_3.apk')]
+
+        with TemporaryDirectory() as tmpdir, TmpCwd(tmpdir):
+            signatures.extract(OptionsFixture)
+
+            # check if extracted signatures are where they are supposed to be
+            # also verify weather if extracted file contian what they should
+            filesAndHashes = (
+                (os.path.join('metadata', 'com.politedroid', 'signatures', '3', 'MANIFEST.MF'),
+                 '7dcd83f0c41a75457fd2311bf3c4578f80d684362d74ba8dc52838d353f31cf2'),
+                (os.path.join('metadata', 'com.politedroid', 'signatures', '3', 'RELEASE.RSA'),
+                 '883ef3d5a6e0bf69d2a58d9e255a7930f08a49abc38e216ed054943c99c8fdb4'),
+                (os.path.join('metadata', 'com.politedroid', 'signatures', '3', 'RELEASE.SF'),
+                 '99fbb3211ef5d7c1253f3a7ad4836eadc9905103ce6a75916c40de2831958284'),
+            )
+            for path, checksum in filesAndHashes:
+                self.assertTrue(os.path.isfile(path),
+                                f'check whether {path!r} was extracted correctly.')
+                with open(path, 'rb') as f:
+                    self.assertEqual(hashlib.sha256(f.read()).hexdigest(), checksum)