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package mkcw
import (
"crypto/rand"
"os"
"path/filepath"
"testing"
"github.com/stretchr/testify/require"
)
func TestReadWriteWorkloadConfig(t *testing.T) {
// Create a temporary file to stand in for a disk image.
temp := filepath.Join(t.TempDir(), "disk.img")
f, err := os.OpenFile(temp, os.O_CREATE|os.O_RDWR, 0o600)
require.NoError(t, err)
err = f.Truncate(0x1000000)
require.NoError(t, err)
defer f.Close()
// Generate a random "encoded workload config".
workloadConfig := make([]byte, 0x100)
n, err := rand.Read(workloadConfig)
require.NoError(t, err)
require.Equal(t, len(workloadConfig), n)
// Read the size of our temporary file.
st, err := f.Stat()
require.NoError(t, err)
originalSize := st.Size()
// Should get an error, since there's no workloadConfig in there to read.
_, err = ReadWorkloadConfigFromImage(f.Name())
require.Error(t, err)
// File should grow, even though we looked for an old config to overwrite.
err = WriteWorkloadConfigToImage(f, workloadConfig, true)
require.NoError(t, err)
st, err = f.Stat()
require.NoError(t, err)
require.Greater(t, st.Size(), originalSize)
originalSize = st.Size()
// File shouldn't grow, even overwriting the config with a slightly larger one.
err = WriteWorkloadConfigToImage(f, append([]byte("slightly longer"), workloadConfig...), true)
require.NoError(t, err)
st, err = f.Stat()
require.NoError(t, err)
require.Equal(t, originalSize, st.Size())
originalSize = st.Size()
// File should grow if we're not trying to replace an old one config with a new one.
err = WriteWorkloadConfigToImage(f, []byte("{\"comment\":\"quite a bit shorter\"}"), false)
require.NoError(t, err)
st, err = f.Stat()
require.NoError(t, err)
require.Greater(t, st.Size(), originalSize)
// Should read successfully.
_, err = ReadWorkloadConfigFromImage(f.Name())
require.NoError(t, err)
}
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