You have a Ruby on Rails application/engine with some tests in Minitest and using postgresql as the db. In the original development environment all the tests that use fixtures and foreign key validations pass, but when you try to move to a different environment with new database some or all of you tests fail with a message that refers to the ForeignKeyViolation as in:
ActiveRecord::InvalidForeignKey: PG::ForeignKeyViolation: ERROR: insert or update on table "tbl_name" violates foreign key constraint "tbl_name_cln_name_fk_tbl_name_fk" DETAIL: Key (col_name)=(VALUE) is not present in table "fk_tbl_name".
Since active record disables the foreign keys before loading the fixtures in the database, the user that you run the tests with needs to have superuser permissions in the test database. Otherwise the fixtures are not loaded. So add the superuser permissions to your user:
psql -U super_user alter role use_for_tests superuser;
You may need to drop and create your test database.