Loading the testthat package only for tests but not requiring in dependencies

Building a package results in the following warning: ``` * checking for unstated dependencies in tests ... WARNING ‘library’ or ‘require’ call not declared from: ‘testthat’ * checking tests ... Running ‘test-all.R’ OK * checking PDF version of manual ... OK WARNING: There was 1 warning. ``` The package directory has a folder called `tests`, with a file test-all.R: ``` library(testthat) library(bootLR) test_package("bootLR") ``` Then a subfolder `testthat` with two files in it that hold the various tests. The error message is likely telling me that I have not declared testthat in the DESCRIPTION file, but I don't want to require its installation by end-users, and I believe that putting the `library(testthat)` statement in the test-all.R file comes from the testthat manual. Any way around this, or do I have to add it in the proper way (that forces uses to install testthat)? Edit: I guess adding it to `Suggests:` might be the best way to do this?