I&#x27;m sure that it persists them to disk but the test suite keeps running at the same speed, so it must happen when it&#x27;s less inconvenient. Buying enough RAM to cache there all the DB is a common recommendation even if it can need some careful configuration <a href="http:&#x2F;&#x2F;dba.stackexchange.com&#x2F;questions&#x2F;18484&#x2F;tuning-postgresql-for-large-amounts-of-ram" rel="nofollow">http:&#x2F;&#x2F;dba.stackexchange.com&#x2F;questions&#x2F;18484&#x2F;tuning-postgres...</a>