Hi,
The manual for current version (10.3) DevTest does not mention about the Couchbase DB connection and "N1QL".
Then I do not think the "SQL Database Execution (JDBC) step" in DevTest can be used for Couchbase DB.
However, there are some possiblities to realize for using Couchbase DB from DevTest by writing java code or writing scripts in "Execute Script(JSR-223) step" with Couchbase JDBC driver, but these are customizations.
Thank you,