The prologue directory has two purposes:

(1) It contains 3rd party software packages that are kept inside of the ESMF
    source tree for easier maintenance. These sources are typically activated
    by setting the respective ESMF_* build environment variable to "internal".
    
(2) The "test" subdirectory contains very basic sanity tests which must be
    passed before any other tests in the framework are even attempted to be
    compiled or run.


