I never claimed that a strict proof is possible, but I do believe that you can become reasonably certain that an AI understands human psychology.

Give the thing a college education in psychology, ethics and philosophy. Ask its opinion on famous philosophical problems. Show it video clips or abstract scenarios about everyday life and ask what it thinks why the people did what they did. Then ask what it would have done in the same situation and if it says it would act differently, ask it why and what it thinks is the difference in motivation between it and the human.

Finally, give it all stories that were ever written about malevolent AIs or paperclip maximizers to read and tell it to comment on that.

Let it write a 1000 page thesis on the dangers of AI.

If do all that you are bound to find any significant misunderstanding.