diff --git a/pkg/util/binaryrw_test.go b/pkg/util/binaryrw_test.go
index 34931afd2..466504057 100644
--- a/pkg/util/binaryrw_test.go
+++ b/pkg/util/binaryrw_test.go
@@ -1,11 +1,122 @@
 package util
 
 import (
+	"errors"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
 )
 
+// mocks io.Reader and io.Writer, always fails to Write() or Read().
+type badRW struct{}
+
+func (w *badRW) Write(p []byte) (int, error) {
+	return 0, errors.New("it always fails")
+}
+
+func (w *badRW) Read(p []byte) (int, error) {
+	return w.Write(p)
+}
+
+func TestWriteLE(t *testing.T) {
+	var (
+		val     uint32 = 0xdeadbeef
+		readval uint32
+		bin     []byte = []byte{0xef, 0xbe, 0xad, 0xde}
+	)
+	bw := NewBufBinWriter()
+	bw.WriteLE(val)
+	assert.Nil(t, bw.Err)
+	wrotebin := bw.Bytes()
+	assert.Equal(t, wrotebin, bin)
+	br := NewBinReaderFromBuf(bin)
+	br.ReadLE(&readval)
+	assert.Nil(t, br.Err)
+	assert.Equal(t, val, readval)
+}
+
+func TestWriteBE(t *testing.T) {
+	var (
+		val     uint32 = 0xdeadbeef
+		readval uint32
+		bin     []byte = []byte{0xde, 0xad, 0xbe, 0xef}
+	)
+	bw := NewBufBinWriter()
+	bw.WriteBE(val)
+	assert.Nil(t, bw.Err)
+	wrotebin := bw.Bytes()
+	assert.Equal(t, wrotebin, bin)
+	br := NewBinReaderFromBuf(bin)
+	br.ReadBE(&readval)
+	assert.Nil(t, br.Err)
+	assert.Equal(t, val, readval)
+}
+
+func TestWriterErrHandling(t *testing.T) {
+	var badio = &badRW{}
+	bw := NewBinWriterFromIO(badio)
+	bw.WriteLE(uint32(0))
+	assert.NotNil(t, bw.Err)
+	// these should work (without panic), preserving the Err
+	bw.WriteLE(uint32(0))
+	bw.WriteBE(uint32(0))
+	bw.WriteVarUint(0)
+	bw.WriteBytes([]byte{0x55, 0xaa})
+	bw.WriteString("neo")
+	assert.NotNil(t, bw.Err)
+}
+
+func TestReaderErrHandling(t *testing.T) {
+	var (
+		i     uint32 = 0xdeadbeef
+		iorig        = i
+		badio        = &badRW{}
+	)
+	br := NewBinReaderFromIO(badio)
+	br.ReadLE(&i)
+	assert.NotNil(t, br.Err)
+	// i shouldn't change
+	assert.Equal(t, i, iorig)
+	// these should work (without panic), preserving the Err
+	br.ReadLE(&i)
+	br.ReadBE(&i)
+	assert.Equal(t, i, iorig)
+	val := br.ReadVarUint()
+	assert.Equal(t, val, uint64(0))
+	b := br.ReadBytes()
+	assert.Equal(t, b, []byte{})
+	s := br.ReadString()
+	assert.Equal(t, s, "")
+	assert.NotNil(t, br.Err)
+}
+
+func TestBufBinWriterErr(t *testing.T) {
+	bw := NewBufBinWriter()
+	bw.WriteLE(uint32(0))
+	assert.Nil(t, bw.Err)
+	// inject error
+	bw.Err = errors.New("oopsie")
+	res := bw.Bytes()
+	assert.NotNil(t, bw.Err)
+	assert.Nil(t, res)
+}
+
+func TestWriteString(t *testing.T) {
+	var (
+		str string = "teststring"
+	)
+	bw := NewBufBinWriter()
+	bw.WriteString(str)
+	assert.Nil(t, bw.Err)
+	wrotebin := bw.Bytes()
+	// +1 byte for length
+	assert.Equal(t, len(wrotebin), len(str)+1)
+	br := NewBinReaderFromBuf(wrotebin)
+	readstr := br.ReadString()
+	assert.Nil(t, br.Err)
+	assert.Equal(t, str, readstr)
+}
+
 func TestWriteVarUint1(t *testing.T) {
 	var (
 		val = uint64(1)
@@ -15,6 +126,10 @@ func TestWriteVarUint1(t *testing.T) {
 	assert.Nil(t, bw.Err)
 	buf := bw.Bytes()
 	assert.Equal(t, 1, len(buf))
+	br := NewBinReaderFromBuf(buf)
+	res := br.ReadVarUint()
+	assert.Nil(t, br.Err)
+	assert.Equal(t, val, res)
 }
 
 func TestWriteVarUint1000(t *testing.T) {