Looks good to me, and it doesn't affect anything specifically here, so I believe we can merge this straight away.

I wonder if doing this instead wouldn't be a better practice (https://cliutils.gitlab.io/modern-cmake/chapters/testing.html):

When you add your test folder, you should do something like this:

if(CMAKE_PROJECT_NAME STREQUAL PROJECT_NAME AND BUILD_TESTING)
    add_subdirectory(tests)
endif()

The reason for this is that if someone else includes your package, and they use BUILD_TESTING, they probably do not want your tests to build.

On the other hand, BUILD_TESTS was added as a project option here, so it should be at least overridable.

And BTW, BUILD_TESTING is apparently a much more common name than BUILD_TESTS.