The various implementations of sccs vary in several different
ways, but the cssc test suite tries very hard to pass when run
against any genuine implementation of sccs unless it has a
definite bug. This means for example that although the cssc
version of admin -i will support automatic switch-over to
binary mode for a file provided via stdin, and the test suite tests
this, the same property is not required of sccs itself.
The real-thing script checks if we are actually tesing a real implementation of sccs. It sets the environment variable TESTING_CSSC to ‘true’ or ‘false’, depending on whether we are testing CSSC or not.
If you are really interested in whether the implementation being tested supports binary files or not, you should be using the config-data script instead.