TIFR :- http://univ.tifr.res.in/gs2020/Imp_Dates/Imp_Dates.htm
JEST :- https://www.jest.org.in/joint-entrance-screening-test
These exams are conducted mainly for admissions in Ph.D / Integrated Ph.D Programme.
JEST score is also accepted for IISc M.Tech. Research admissions
Please visit their official website for further details.