Make a tested instance

For now, a single STK/Unit instance tries to test itself using 2 TCs (1 for assertions, the other for the core library). This is not bad for assertions, which can be completely tested. But of course only some procedures from the core lib can be tested this way.

This blueprint aims to make a separate instance of STK/Unit which will be tested by the main instance.

This will be possible when Macros will be implemented (in another STK project). In the main .sql file, the database name will be a Macro, so that it will be possible to transform it in the main instance or in the tested instance, simply by specifying 2 different values as DB name. Other files will contain references both to the main instance and to the tested instance (because they will use one instance to test the other one).

This feature is needed to test some planned features.