WPF Combobox have no ClickItem
There are lots of possible answers to your question that we have found for you. Have you tried any of them?
As tristaanogre and I have continued to explain, there may not be a ClickItem option for your object. This means you will have to change your test. Arguing with us about it will get you nowhere.
Here's the link to Support. You can ask them your question directly.