Medical certificate can be issued by any general practitioner provided you've consulted in person.
A specialist thus can also surely assist you in doing so.
Regarding tests, it will be prescribed before providing the certificate and depends on your clinical condition and history.
Usually a complete blood test profile including cbc, serology for
HIV, HBSAG, HCV , RFT,
LFT,
LIPID PROFILE, CXR and USG are sufficient but lie at the discretion of the attending physician.