Expand sparseWriter tests

- Add more test cases
- Test that we create the expected (large) holes;
  don't enforce anything for the <zerosThresholt ones.

O)nly changes test code, should not change behavior.

Signed-off-by: Miloslav Trmač <mitr@redhat.com>

pkg/machine/compression/sparse_file_writer_test.go

@@ -3,22 +3,32 @@ package compression
 import (
 	"bytes"
 	"errors"
+	"fmt"
 	"io"
 	"testing"
+
+	"github.com/sirupsen/logrus"
+	"github.com/stretchr/testify/assert"
 )
 
 type memorySparseFile struct {
 	buffer bytes.Buffer
 	pos    int64
+	sparse int64
 }
 
 func (m *memorySparseFile) Seek(offset int64, whence int) (int64, error) {
+	logrus.Debugf("Seek %d %d", offset, whence)
 	var newPos int64
 	switch whence {
 	case io.SeekStart:
-		newPos = offset
+		panic("unexpected")
 	case io.SeekCurrent:
 		newPos = m.pos + offset
+		if offset < -1 {
+			panic("unexpected")
+		}
+		m.sparse += offset
 	case io.SeekEnd:
 		newPos = int64(m.buffer.Len()) + offset
 	default:
@@ -34,6 +44,7 @@ func (m *memorySparseFile) Seek(offset int64, whence int) (int64, error) {
 }
 
 func (m *memorySparseFile) Write(b []byte) (n int, err error) {
+	logrus.Debugf("Write %d", len(b))
 	if int64(m.buffer.Len()) < m.pos {
 		padding := make([]byte, m.pos-int64(m.buffer.Len()))
 		_, err := m.buffer.Write(padding)
@@ -42,8 +53,6 @@ func (m *memorySparseFile) Write(b []byte) (n int, err error) {
 		}
 	}
 
-	m.buffer.Next(int(m.pos) - m.buffer.Len())
-
 	n, err = m.buffer.Write(b)
 	m.pos += int64(n)
 	return n, err
@@ -53,7 +62,7 @@ func (m *memorySparseFile) Close() error {
 	return nil
 }
 
-func testInputWithWriteLen(t *testing.T, input []byte, chunkSize int) {
+func testInputWithWriteLen(t *testing.T, input []byte, minSparse int64, chunkSize int) {
 	m := &memorySparseFile{}
 	sparseWriter := NewSparseWriter(m)
 
@@ -71,15 +80,16 @@ func testInputWithWriteLen(t *testing.T, input []byte, chunkSize int) {
 	if err != nil {
 		t.Fatalf("Expected no error, got %v", err)
 	}
-	if !bytes.Equal(input, m.buffer.Bytes()) {
-		t.Fatalf("Incorrect output")
-	}
+	assert.Equal(t, string(input), m.buffer.String())
+	assert.GreaterOrEqual(t, m.sparse, minSparse)
 }
 
-func testInput(t *testing.T, inputBytes []byte) {
+func testInput(t *testing.T, name string, inputBytes []byte, minSparse int64) {
 	currentLen := 1
 	for {
-		testInputWithWriteLen(t, inputBytes, currentLen)
+		t.Run(fmt.Sprintf("%s@%d", name, currentLen), func(t *testing.T) {
+			testInputWithWriteLen(t, inputBytes, minSparse, currentLen)
+		})
 		currentLen <<= 1
 		if currentLen > len(inputBytes) {
 			break
@@ -88,22 +98,30 @@ func testInput(t *testing.T, inputBytes []byte) {
 }
 
 func TestSparseWriter(t *testing.T) {
-	testInput(t, []byte("hello"))
-	testInput(t, append(make([]byte, 100), []byte("hello")...))
-	testInput(t, []byte(""))
+	testInput(t, "small contents", []byte("hello"), 0)
+	testInput(t, "small zeroes", append(make([]byte, 100), []byte("hello")...), 0)
+	testInput(t, "empty", []byte(""), 0)
+	testInput(t, "small iterated", []byte{'a', 0, 'a', 0, 'a', 0}, 0)
+	testInput(t, "small iterated2", []byte{0, 'a', 0, 'a', 0, 'a'}, 0)
 
 	// add "hello" at the beginning
-	largeInput := make([]byte, 1024*1024)
+	const largeSize = 1024 * 1024
+	largeInput := make([]byte, largeSize)
 	copy(largeInput, []byte("hello"))
-	testInput(t, largeInput)
+	testInput(t, "sparse end", largeInput, largeSize-5-1) // -1 for the final byte establishing file size
 
 	// add "hello" at the end
-	largeInput = make([]byte, 1024*1024)
-	copy(largeInput[1024*1024-5:], []byte("hello"))
-	testInput(t, largeInput)
+	largeInput = make([]byte, largeSize)
+	copy(largeInput[largeSize-5:], []byte("hello"))
+	testInput(t, "sparse beginning", largeInput, largeSize-5)
 
 	// add "hello" in the middle
-	largeInput = make([]byte, 1024*1024)
+	largeInput = make([]byte, largeSize)
 	copy(largeInput[len(largeInput)/2:], []byte("hello"))
-	testInput(t, largeInput)
+	testInput(t, "sparse both ends", largeInput, largeSize-5-1) // -1 for the final byte establishing file size
+
+	largeInput = make([]byte, largeSize)
+	copy(largeInput[0:5], []byte("hello"))
+	copy(largeInput[largeSize-5:], []byte("HELLO"))
+	testInput(t, "sparse middle", largeInput, largeSize-10)
 }