Add test case: test_report_available_mirrors to test that print the…

… available mirrors to the terminal.

apt_mirror_updater/tests.py

@@ -77,6 +77,11 @@ def test_current_mirror_discovery(self):
         assert exit_code == 0
         check_mirror_url(output.strip())
 
+    def test_report_available_mirrors(self):
+        """Test that print the available mirrors to the terminal."""
+        exit_code, output = run_cli(main, '--list-mirrors')
+        assert exit_code == 0
+
     def test_dumb_update(self):
         """Test that our dumb ``apt-get update`` wrapper works."""
         if os.getuid() != 0: