Add more information on running the tests, together with a section on how the tests are organised, aimed at new developers. (cherry picked from commitaf005cdbcf) (cherry picked from commit3952d4631e) (cherry picked from commit67f135c1d0)
Add more information on running the tests, together with a section on how the tests are organised, aimed at new developers. (cherry picked from commitaf005cdbcf) (cherry picked from commit3952d4631e) (cherry picked from commit67f135c1d0)