I’ve noticed liquibase do not drop sequences in postgres in case dropFirst is true.
(tested on postgres 9.3, liquibase 3.1.1, 3.3.2)
in case it is a bug I can submit a bug request to jira.
as a workaround one can add the following to the begin of the db-changelog.sql file
–changeset youName:1 context:test failOnError:true
DROP SEQUENCE IF EXISTS your_sequence;
PS Thank you for supporting this great project!