Japanese Language Proficiency Test (JLPT)
The Japanese-Language Proficiency Test (JLPT) under joint organization of the Japan Foundation and Japan Educational Exchanges and Services (previously Association of International Education, Japan) started in 1984 as a test to measure and certify the Japanese-language proficiency of those whose native language is not Japanese. A JLPT N1 certificate is required for medical practitioners licensed overseas who want to take Japan's national exams for medical practitioners, and other professions.
For exam preparation, please refer to the official website of the Japanese Language Proficiency Test, where you can find sample questions and various other materials and information. You can also study online, for example on Youtube, so find a study style that suits you and aim to pass the N1. It is also very important to acquire the language by making friends who speak Japanese as their native language through SNS and other means before coming to Japan, and increasing the opportunities to speak and listen to the language. Japanese is said to be the most difficult language in the world to learn. Even if you pass the N1, there are still many Japanese phrases, Japanese-English words, and industry-specific terms (so-called industry jargon) that will make you struggle in real-life situations. However, I think there are many things you can overcome by sharing your thoughts with friends who have studied Japanese with you.