Add tests and fix conditional.

x/io/int.go

@@ -66,31 +66,31 @@ func ReadVarint(data []byte) (n int64, bytesRead int, err error) {
 
 // VarintBytes returns the number of bytes required to encode a varint.
 func VarintBytes(v int64) int {
-	if v < one || v >= -one {
+	if v < one && v >= -one {
 		return 1
 	}
-	if v < two || v >= -two {
+	if v < two && v >= -two {
 		return 2
 	}
-	if v < three || v >= -three {
+	if v < three && v >= -three {
 		return 3
 	}
-	if v < four || v >= -four {
+	if v < four && v >= -four {
 		return 4
 	}
-	if v < five || v >= -five {
+	if v < five && v >= -five {
 		return 5
 	}
-	if v < six || v >= -six {
+	if v < six && v >= -six {
 		return 6
 	}
-	if v < seven || v >= -seven {
+	if v < seven && v >= -seven {
 		return 7
 	}
-	if v < eight || v >= -eight {
+	if v < eight && v >= -eight {
 		return 8
 	}
-	if v < nine || v >= -nine {
+	if v < nine && v >= -nine {
 		return 9
 	}
 	return binary.MaxVarintLen64

x/io/int_test.go

@@ -0,0 +1,41 @@
+package io
+
+import (
+	"encoding/binary"
+	"math"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestVarintBytes(t *testing.T) {
+	buf := make([]byte, binary.MaxVarintLen64)
+	lowerBounds := []int64{
+		-one,
+		-two,
+		-three,
+		-four,
+		-five,
+		-six,
+		-seven,
+		-eight,
+		-nine,
+	}
+	upperBounds := []int64{
+		one - 1,
+		two - 1,
+		three - 1,
+		four - 1,
+		five - 1,
+		six - 1,
+		seven - 1,
+		eight - 1,
+		nine - 1,
+	}
+	for idx := 0; idx < len(upperBounds); idx++ {
+		require.Equal(t, binary.PutVarint(buf, upperBounds[idx]), VarintBytes(upperBounds[idx]))
+		require.Equal(t, binary.PutVarint(buf, lowerBounds[idx]), VarintBytes(lowerBounds[idx]))
+	}
+	require.Equal(t, binary.PutVarint(buf, math.MaxInt64), VarintBytes(math.MaxInt64))
+	require.Equal(t, binary.PutVarint(buf, math.MinInt64), VarintBytes(math.MinInt64))
+}