first look at setting accum to large negative number (-total_power):

- commit to run all tests on circleci
- potential quick-fix for #2718

additional unrelated changes:
- do not capitalize error msgs
- fix typo

lite/doc.go

@@ -121,7 +121,7 @@ If we cannot update directly from H -> H' because there was too much change to
 the validator set, then we can look for some Hm (H < Hm < H') with a validator
 set Vm.  Then we try to update H -> Hm and then Hm -> H' in two steps.  If one
 of these steps doesn't work, then we continue bisecting, until we eventually
-have to externally validate the valdiator set changes at every block.
+have to externally validate the validator set changes at every block.
 
 Since we never trust any server in this protocol, only the signatures
 themselves, it doesn't matter if the seed comes from a (possibly malicious)

state/execution.go

@@ -326,11 +326,12 @@ func updateValidators(currentSet *types.ValidatorSet, abciUpdates []abci.Validat
 	if err != nil {
 		return err
 	}
-
+	// store the current total voting power before applying any updates
+	totalVotingPower := currentSet.TotalVotingPower()
 	// these are tendermint types now
 	for _, valUpdate := range updates {
 		if valUpdate.VotingPower < 0 {
-			return fmt.Errorf("Voting power can't be negative %v", valUpdate)
+			return fmt.Errorf("voting power can't be negative %v", valUpdate)
 		}
 
 		address := valUpdate.Address
@@ -339,19 +340,21 @@ func updateValidators(currentSet *types.ValidatorSet, abciUpdates []abci.Validat
 			// remove val
 			_, removed := currentSet.Remove(address)
 			if !removed {
-				return fmt.Errorf("Failed to remove validator %X", address)
+				return fmt.Errorf("failed to remove validator %X", address)
 			}
 		} else if val == nil {
-			// add val
+			// set accum to -totalVotingPower to make sure validators can't unbond/rebond to reset their accum to zero:
+			valUpdate.Accum = -totalVotingPower
+			// add validator
 			added := currentSet.Add(valUpdate)
 			if !added {
-				return fmt.Errorf("Failed to add new validator %v", valUpdate)
+				return fmt.Errorf("failed to add new validator %v", valUpdate)
 			}
 		} else {
 			// update val
 			updated := currentSet.Update(valUpdate)
 			if !updated {
-				return fmt.Errorf("Failed to update validator %X to %v", address, valUpdate)
+				return fmt.Errorf("failed to update validator %X to %v", address, valUpdate)
 			}
 		}
 	}

types/validator.go

@@ -81,13 +81,13 @@ func (v *Validator) Hash() []byte {
 // as its redundant with the pubkey. This also excludes accum which changes
 // every round.
 func (v *Validator) Bytes() []byte {
-	return cdcEncode((struct {
+	return cdcEncode(struct {
 		PubKey      crypto.PubKey
 		VotingPower int64
 	}{
 		v.PubKey,
 		v.VotingPower,
-	}))
+	})
 }
 
 //----------------------------------------