Hi Chetna,
From http://manual.gromacs.org/documentation/current/install-guide/index.html:
Alternatively, you can download and unpack the GROMACS regression test suite http://gerrit.gromacs.org/download/regressiontests-2020.3.tar.gz tarball yourself and use the advanced cmake option REGRESSIONTEST_PATH to specify the path to the unpacked tarball, which will then be used for testing
Give that a try.
Dan