Add a cleartext test file with a detached signature.

mayan/apps/django_gpg/tests/contrib/test_files/test_file.txt

@@ -0,0 +1 @@
+test_file content

mayan/apps/django_gpg/tests/contrib/test_files/test_file.txt.asc

@@ -0,0 +1,11 @@
+-----BEGIN PGP SIGNATURE-----
+Version: GnuPG v1
+
+iQEcBAABAgAGBQJW8z8CAAoJEEEl6cVx83isoK0IAKa7TGyBBhebx/EM8/tzKwgd
+mKmXFtgpSoJhqoLZiBdFVP4gJtxfaDnqSFt7uQA69V0TMqI6cIuX0x7h0lRrNLea
++FQZGsa8HwnJzsTQXIRzszY/wvvFyHfk8jYjBQi7BRwg5kZdW5fUgprYsE8j08WA
+cn/VAP5xigxKJfM0ny3pL3mbJj7rdoz+bEu4z7yMg5EsRLbF4MZDU9mUo5QjAvQg
+oMMIjv6fFpuvBP9xY/D03IstyqoEEfwl/+36ZQwyGNsA3ZHWXgSb5fwcpXWPdqaD
+PuX5l137B2VHz9YNPK9sJdnr5ZRyY0vebzkAvCFPfysAaGWH36iTE58V3uhLNMk=
+=yL7D
+-----END PGP SIGNATURE-----

mayan/apps/django_gpg/tests/literals.py

@@ -4,6 +4,16 @@ import os
 
 from django.conf import settings
 
+TEST_DETACHED_SIGNATURE = os.path.join(
+    settings.BASE_DIR, 'mayan', 'apps', 'django_gpg', 'tests', 'contrib',
+    'test_files', 'test_file.txt.asc'
+)
+
+TEST_FILE = os.path.join(
+    settings.BASE_DIR, 'mayan', 'apps', 'django_gpg', 'tests', 'contrib',
+    'test_files', 'test_file.txt'
+)
+
 TEST_KEY_DATA = '''-----BEGIN PGP PRIVATE KEY BLOCK-----
 Version: GnuPG v1