package readers import (	"io"	"testing" 	"github.com/stretchr/testify/assert"	"github.com/stretchr/testify/require") func TestPatternReader(t *testing.T) {	b2 := make([]byte, 1) 	r := NewPatternReader(0)	b, err := io.ReadAll(r)	require.NoError(t, err)	assert.Equal(t, []byte{}, b)	n, err := r.Read(b2)	require.Equal(t, io.EOF, err)	require.Equal(t, 0, n) 	r = NewPatternReader(10)	b, err = io.ReadAll(r)	require.NoError(t, err)	assert.Equal(t, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}, b)	n, err = r.Read(b2)	require.Equal(t, io.EOF, err)	require.Equal(t, 0, n)} func TestPatternReaderSeek(t *testing.T) {	r := NewPatternReader(1024)	b, err := io.ReadAll(r)	require.NoError(t, err) 	for i := range b {		assert.Equal(t, byte(i%251), b[i])	} 	n, err := r.Seek(1, io.SeekStart)	require.NoError(t, err)	assert.Equal(t, int64(1), n) 	// pos 1 	b2 := make([]byte, 10)	nn, err := r.Read(b2)	require.NoError(t, err)	assert.Equal(t, 10, nn)	assert.Equal(t, b[1:11], b2) 	// pos 11 	n, err = r.Seek(9, io.SeekCurrent)	require.NoError(t, err)	assert.Equal(t, int64(20), n) 	// pos 20 	nn, err = r.Read(b2)	require.NoError(t, err)	assert.Equal(t, 10, nn)	assert.Equal(t, b[20:30], b2) 	n, err = r.Seek(-24, io.SeekEnd)	require.NoError(t, err)	assert.Equal(t, int64(1000), n) 	// pos 1000 	nn, err = r.Read(b2)	require.NoError(t, err)	assert.Equal(t, 10, nn)	assert.Equal(t, b[1000:1010], b2) 	// Now test errors 	n, err = r.Seek(1, 400)	require.Error(t, err)	assert.Contains(t, err.Error(), "invalid whence")	assert.Equal(t, int64(0), n) 	n, err = r.Seek(-1, io.SeekStart)	require.Error(t, err)	assert.Contains(t, err.Error(), "negative position")	assert.Equal(t, int64(0), n)}