Executing this test method leads to an error MCStReaderTest debug: #testCommentWithStyle SmallInteger>>/ Job>>progress JobChange>>progress SystemProgressMorph class>>updateJob: MessageSend>>value: MessageSend>>cull: MessageSend>>cull:cull: AnnouncementSubscription>>deliver: in Block: [action cull: anAnnouncement cull: announcer] BlockClosure>>on:do: BlockClosure>>on:fork: in Block: [Processor terminateActive] testCommentWithStyle "self debug: #testCommentWithStyle" | reader | reader := MCStReader on: self commentWithStyle readStream. reader definitions But the error is raised by the progress bar Job>>progress ^ (currentValue - min) / (max - min) Raises a ZeroDivide Because max and min are equal to 1. What is really strange is that if I try with another test - green it will run perfectly - if I introduce a bug in another green test it will run and lead to the debugger and not the error SmallInteger>>/ Job>>progress JobChange>>progress SystemProgressMorph class>>updateJob: MessageSend>>value: MessageSend>>cull: MessageSend>>cull:cull: AnnouncementSubscription>>deliver: in Block: [action cull: anAnnouncement cull: announcer] BlockClosure>>on:do: BlockClosure>>on:fork: in Block: [Processor terminateActive]