Hi,
I am not really excited about another DBMS pretending to be Postgres but then only supporting a sub-set of the features (Redshift, CockroachDB tried the same thing and it turns out to be a real nuisance for tool developers).
The "test suite" is the the Unit tests that test the Postgres specific features in SQL Workbench (they can be run using "mvn -Ptest-postgres test").
I tried it out and about 70% of all tests fail "out-of-the-box" because the Postgres JDBC driver states that the DBMS supports savepoints, but then the backend doesnt't. I make quite extensive use of Savepoints to avoid breaking transactions in non-autocommit mode.
I implemented a workaround to overwrite the JDBC driver's opinion on what the backend supports and then things look a better.
Note that with the next release, SQL Workbench/J will require Java 11, so maybe you want to at least add the recommendation about using Java 11.
Regards
Thomas