Identity columns in Datagrip and PostgreSQL 10?

I'm transitioning from MySQL to PostgreSQL 10, and am using Datagrip.

I made my columns that were previously auto-incremented in MySQL into integer primary keys in PostgreSQL. I then ran:

ALTER TABLE test_new
    ALTER COLUMN id ADD GENERATED BY DEFAULT AS IDENTITY;

for each relevant table. Now, I'm getting problems when I try to insert a new row. Mostly that I am violating the constraint of the primary key. 

It seems that a sequence is out of order. When I generated the DDL code, it looks like my column is actually converted to a serial with a sequence..

id serial not null
 constraint pk_test_new
  primary key

Am I understanding this incorrectly? And shouldn't the identity generate the correct sequence? If I am understanding this incorrectly, how can I update my sequence so that I can insert data..