To test the authenticity of Xiamen University's diploma, you can refer to the following methods:

1. Verify that the style and layout of the certificate meet the standards. You can download the comparison standard certificate from the school official website for verification.

2. Check whether the text and format on the certificate are standard. A real certificate usually has complete information such as the student's name, student number, major and graduation date.

3. Check whether the seal and signature on the certificate are legal. You can contact the school or relevant departments to verify the authenticity of the seal and signature.

4. You can try to verify the authenticity of the certificate through the electronic inquiry system or call the official phone of the school.

Generally speaking, the identification of the authenticity of a certificate requires verification in many aspects. At the same time, we should pay special attention to some obvious defects of certificates, such as the authenticity of paper, uneven printing, gloomy handwriting and skewed watermark.