Run all the tests that are in sub directories in a unique file using testthat

When we use testthat in R, the package looks in tests/testthat directory and execute all the files that starts with 'test'... but if i have this type of organization:

tests

--/testthat

----/case1

------/Test1.R

------/Test2.R

----/case2

------/Test3.R

----/..

How can I execute all the tests in a unique command or file? I try to change the path of testthat tests to 'tests/testthat/**/*.R' but testthat not iterate over directories. Anybody knows a solution?