Starting

Attaching successful invariant that makes an update

Attaching successful invariant that uses retry&orelse internally

Attaching a failed invariant that makes an update
Caught: Exn raised in invariant

Attaching an invariant that blocks

Another update to the TVar with the blocking invariant

Update the TVar to cause the invariant to block again (expect thread blocked indef)
Caught: thread blocked indefinitely in an STM transaction