Wait for instructions once you have submitted your application.
We’ll send you instructions on how to get your medical exam done. You must go for your medical exam
within 30 daysof receiving these instructions.
If you do not follow these instructions, we may refuse your application.
https://www.canada.ca/en/immigratio...l-exams/requirements-permanent-residents.html
These instructions from CIC site are post application, so I believe after submitting your application, if they want you to get additional tests done, then they will notify you and in that case you should get those medical exams done within 30 days or else your application will be rejected,