Add test to cover when terminal is not a TTY

tests/test_cli.py

@@ -57,6 +57,19 @@ def patched_sys_stdin_read():
 
         assert 'There was an error decoding the token' in str(excinfo.value)
 
+    def test_decode_payload_raises_terminal_not_a_tty(self, monkeypatch):
+        decode_args = ['--key', '1234', 'decode']
+        parser = build_argparser()
+        args = parser.parse_args(decode_args)
+
+        monkeypatch.setattr(sys.stdin, 'isatty', lambda: False)
+        monkeypatch.setattr(sys.stdin, 'read', lambda: 'token')
+
+        with pytest.raises(IOError) as excinfo:
+            decode_payload(args)
+            assert 'Cannot read from stdin: terminal not a TTY' \
+                in str(excinfo.value)
+
     @pytest.mark.parametrize('key,name,job,exp,verify', [
         ('1234', 'Vader', 'Sith', None, None),
         ('4567', 'Anakin', 'Jedi', '+1', None),