fix: itest: fix wdpost proving epoch calculation

Fixes: #12091

itests/kit/node_unmanaged.go

@@ -603,6 +603,9 @@ func (tm *TestUnmanagedMiner) wdPostLoop(ctx context.Context, sectorNumber abi.S
 
 			err = tm.submitWindowPost(ctx, sectorNumber, sealedCid, sealedPath, cacheDir)
 			writeRespF(err) // send an error, or first post, or nothing if no error and this isn't the first post
+			if err != nil {
+				return
+			}
 			postCount++
 			tm.t.Logf("Sector %d: WindowPoSt #%d submitted", sectorNumber, postCount)
 		}
@@ -846,15 +849,18 @@ func (tm *TestUnmanagedMiner) calculateNextPostEpoch(
 
 	// Calculate the start of the period, adjusting if the current deadline has passed
 	periodStart := di.PeriodStart
-	if di.PeriodStart < di.CurrentEpoch && sp.Deadline <= di.Index && di.Open <= di.CurrentEpoch {
+	if di.Open > di.CurrentEpoch {
+		// special case, first sector onboarded, cron hasn't run deadline tick yet
+		periodStart = di.PeriodStart + di.WPoStProvingPeriod
+	} else if di.PeriodStart < di.CurrentEpoch && sp.Deadline <= di.Index {
 		// If the deadline has passed in the current proving period, calculate for the next period
 		// Note that di.Open may be > di.CurrentEpoch if the miner has just been enrolled in cron so
 		// their deadlines haven't started rolling yet
 		periodStart += di.WPoStProvingPeriod
 	}
 
 	// Calculate the exact epoch when proving should occur
-	provingEpoch := periodStart + (di.WPoStProvingPeriod/abi.ChainEpoch(di.WPoStPeriodDeadlines))*abi.ChainEpoch(sp.Deadline)
+	provingEpoch := periodStart + di.WPoStChallengeWindow*abi.ChainEpoch(sp.Deadline)
 
 	tm.t.Logf("Miner %s: WindowPoST(%d): next ProvingEpoch: %d", tm.ActorAddr, sectorNumber, provingEpoch)