We define a CMake configuration toggle ENABLE_TESTS which toggles whether we build testing targets. CMake's default CTest module defines a toggle BUILD_TESTING which is the standard way to toggle test building within a CMake project.

Additionally: the test target should not be EXCLUDE_FROM_ALL by default, as they exercise a lot of compile-time checks that are useful in general. If packagers/users want to exclude test-libmongoc from building, they should either set BUILD_TESTING=FALSE or name the targets they want to build.

Additionally additionally: More targets should be properly gated behind BUILD_TESTING, rather than doing anything clever with EXCLUDE_FROM_ALL.