Laravel 8 RefreshDatabase no longer working

[henrywhitaker3]

• Laravel Version: 8.31.0
• PHP Version: 7.4.9
• Database Driver & Version: pdo_sqlite 3.33.0

Description:

I've just upgraded an app from v7 to v8, when running tests they mostly fail, with the error

Integrity constraint violation: 19 UNIQUE constraint failed

In my phpunit.xml, I have

<server name="DB_CONNECTION" value="sqlite"/>
<server name="DB_DATABASE" value=":memory:"/>

If I comment out the :memory line, the tests start passing again.