The tests include rocky/json.h, which in turn includes nlohmann/json.hpp. This is a private depedency of Rocky, so this include statement is not transitive. It fails to build. vcpkg builds do not see this because the vcpkg install directory is part of the include path, and this file is under it.

One solution is to make the JSON dependency public in Rocky, but header docs strongly suggest this is not the right path. A better path is to make the test add in the JSON dependency.

The find_package is required because the library is scoped to the src/rocky/ directory.