IncrementAccum upon RPC /validators; Sanity checks and comments (#2808)

types/validator_set.go

@@ -62,7 +62,11 @@ func (vals *ValidatorSet) CopyIncrementAccum(times int) *ValidatorSet {
 
 // IncrementAccum increments accum of each validator and updates the
 // proposer. Panics if validator set is empty.
+// `times` must be positive.
 func (vals *ValidatorSet) IncrementAccum(times int) {
+	if times <= 0 {
+		panic("Cannot call IncrementAccum with non-positive times")
+	}
 
 	// Add VotingPower * times to each validator and order into heap.
 	validatorsHeap := cmn.NewHeap()

types/validator_set_test.go

@@ -86,6 +86,19 @@ func TestCopy(t *testing.T) {
 	}
 }
 
+// Test that IncrementAccum requires positive times.
+func TestIncrementAccumPositiveTimes(t *testing.T) {
+	vset := NewValidatorSet([]*Validator{
+		newValidator([]byte("foo"), 1000),
+		newValidator([]byte("bar"), 300),
+		newValidator([]byte("baz"), 330),
+	})
+
+	assert.Panics(t, func() { vset.IncrementAccum(-1) })
+	assert.Panics(t, func() { vset.IncrementAccum(0) })
+	vset.IncrementAccum(1)
+}
+
 func BenchmarkValidatorSetCopy(b *testing.B) {
 	b.StopTimer()
 	vset := NewValidatorSet([]*Validator{})
@@ -239,7 +252,7 @@ func TestProposerSelection3(t *testing.T) {
 		mod := (cmn.RandInt() % 5) + 1
 		if cmn.RandInt()%mod > 0 {
 			// sometimes its up to 5
-			times = cmn.RandInt() % 5
+			times = (cmn.RandInt() % 4) + 1
 		}
 		vset.IncrementAccum(times)