Use even more stubs to get more complex completions for e.g. strings working

test/test_api/test_interpreter.py

@@ -167,6 +167,14 @@ def test_list():
                                  ['upper'])
 
 
+def test_getattr():
+    class Foo1:
+        bar = []
+    baz = 'bar'
+    _assert_interpreter_complete('getattr(Foo1, baz).app', locals(), ['append'])
+
+
+@pytest.mark.xfail(reason='For now slicing on strings is not supported for mixed objects')
 def test_slice():
     class Foo1:
         bar = []