You are not sure if the username and password to a PostgreSQL database work. What do you do?
Run this one-line command:
psql -d "postgresql://jdoe:coolpassword@localhost/foobardb" -c "select now()"
# Replace "jdoe" with the SQL database username
# Replace "coolpassword" with the user's password
# Replace "foobardb" with the name of the database you are authenticating too
# If you have the PostgreSQL client installed (so psql works) and the database is remote, use the FQDN instead of the "localhost"
This solution was based on this posting.