test(codec): add tests for raw and tar codecs (#450)

* test(codec): add tests for raw and tar codecs

Signed-off-by: Rishi Jat <rishijat098@gmail.com>

* address copilot review

Signed-off-by: Rishi Jat <rishijat098@gmail.com>

---------

Signed-off-by: Rishi Jat <rishijat098@gmail.com>

Author: rishi-jat

pkg/codec/codec_test.go

@@ -0,0 +1,227 @@
+/*
+ *     Copyright 2025 The CNAI Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package codec
+
+import (
+	"bytes"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// --- Raw Codec Tests ---
+
+func TestRawEncodeDecode(t *testing.T) {
+	t.Parallel()
+	dir := t.TempDir()
+	content := []byte("hello world raw codec test")
+
+	// Write source file.
+	srcPath := filepath.Join(dir, "input.bin")
+	require.NoError(t, os.WriteFile(srcPath, content, 0644))
+
+	r := newRaw()
+
+	// Encode: should return a reader with the file's content.
+	reader, err := r.Encode(srcPath, dir)
+	require.NoError(t, err)
+	if c, ok := reader.(io.Closer); ok {
+		t.Cleanup(func() { _ = c.Close() })
+	}
+
+	encoded, err := io.ReadAll(reader)
+	require.NoError(t, err)
+	assert.Equal(t, content, encoded)
+
+	// Decode: write the encoded bytes to an output directory.
+	outputDir := filepath.Join(dir, "output")
+	require.NoError(t, os.MkdirAll(outputDir, 0755))
+
+	desc := ocispec.Descriptor{Size: int64(len(content))}
+	err = r.Decode(outputDir, "decoded.bin", bytes.NewReader(encoded), desc)
+	require.NoError(t, err)
+
+	decoded, err := os.ReadFile(filepath.Join(outputDir, "decoded.bin"))
+	require.NoError(t, err)
+	assert.Equal(t, content, decoded)
+}
+
+func TestRawEncodeEmpty(t *testing.T) {
+	t.Parallel()
+	dir := t.TempDir()
+	content := []byte{}
+
+	srcPath := filepath.Join(dir, "empty.bin")
+	require.NoError(t, os.WriteFile(srcPath, content, 0644))
+
+	r := newRaw()
+
+	reader, err := r.Encode(srcPath, dir)
+	require.NoError(t, err)
+	if c, ok := reader.(io.Closer); ok {
+		t.Cleanup(func() { _ = c.Close() })
+	}
+
+	encoded, err := io.ReadAll(reader)
+	require.NoError(t, err)
+	assert.Empty(t, encoded)
+}
+
+func TestRawDecodeInvalidInput(t *testing.T) {
+	t.Parallel()
+	dir := t.TempDir()
+	r := newRaw()
+
+	// Decode from a reader that always errors; the error should propagate.
+	badReader := &errorReader{}
+	desc := ocispec.Descriptor{Size: 10}
+
+	err := r.Decode(dir, "out.bin", badReader, desc)
+	assert.Error(t, err)
+}
+
+// errorReader is a reader that always returns an error.
+type errorReader struct{}
+
+func (e *errorReader) Read([]byte) (int, error) {
+	return 0, io.ErrUnexpectedEOF
+}
+
+// --- Tar Codec Tests ---
+
+func TestTarArchiveSingleFile(t *testing.T) {
+	t.Parallel()
+	srcDir := t.TempDir()
+	content := []byte("single file content")
+
+	filePath := filepath.Join(srcDir, "file.txt")
+	require.NoError(t, os.WriteFile(filePath, content, 0644))
+
+	c := newTar()
+
+	reader, err := c.Encode(filePath, srcDir)
+	require.NoError(t, err)
+	if c, ok := reader.(io.Closer); ok {
+		t.Cleanup(func() { _ = c.Close() })
+	}
+
+	// Read the tar stream fully so it can be used for extraction.
+	tarData, err := io.ReadAll(reader)
+	require.NoError(t, err)
+	assert.NotEmpty(t, tarData)
+
+	// Extract and verify.
+	extractDir := t.TempDir()
+	desc := ocispec.Descriptor{}
+	err = c.Decode(extractDir, "file.txt", bytes.NewReader(tarData), desc)
+	require.NoError(t, err)
+
+	extracted, err := os.ReadFile(filepath.Join(extractDir, "file.txt"))
+	require.NoError(t, err)
+	assert.Equal(t, content, extracted)
+}
+
+func TestTarArchiveMultipleFiles(t *testing.T) {
+	t.Parallel()
+	srcDir := t.TempDir()
+
+	files := map[string]string{
+		"a.txt":     "content of a",
+		"b.txt":     "content of b",
+		"sub/c.txt": "content of c in sub",
+	}
+
+	for name, data := range files {
+		p := filepath.Join(srcDir, name)
+		require.NoError(t, os.MkdirAll(filepath.Dir(p), 0755))
+		require.NoError(t, os.WriteFile(p, []byte(data), 0644))
+	}
+
+	c := newTar()
+
+	// Archive the entire directory.
+	reader, err := c.Encode(srcDir, filepath.Dir(srcDir))
+	require.NoError(t, err)
+	if c, ok := reader.(io.Closer); ok {
+		t.Cleanup(func() { _ = c.Close() })
+	}
+
+	tarData, err := io.ReadAll(reader)
+	require.NoError(t, err)
+	assert.NotEmpty(t, tarData)
+
+	// Extract.
+	extractDir := t.TempDir()
+	desc := ocispec.Descriptor{}
+	err = c.Decode(extractDir, "", bytes.NewReader(tarData), desc)
+	require.NoError(t, err)
+
+	// The archive was created relative to filepath.Dir(srcDir), so the
+	// extracted tree includes the base name of srcDir as a prefix.
+	base := filepath.Base(srcDir)
+	for name, expected := range files {
+		got, err := os.ReadFile(filepath.Join(extractDir, base, name))
+		require.NoError(t, err, "reading extracted file %s", name)
+		assert.Equal(t, expected, string(got))
+	}
+}
+
+func TestTarExtractRoundtrip(t *testing.T) {
+	t.Parallel()
+	srcDir := t.TempDir()
+	content := []byte("roundtrip data 1234567890")
+
+	require.NoError(t, os.WriteFile(filepath.Join(srcDir, "data.bin"), content, 0644))
+
+	c := newTar()
+
+	// Encode.
+	reader, err := c.Encode(filepath.Join(srcDir, "data.bin"), srcDir)
+	require.NoError(t, err)
+	if c, ok := reader.(io.Closer); ok {
+		t.Cleanup(func() { _ = c.Close() })
+	}
+
+	tarData, err := io.ReadAll(reader)
+	require.NoError(t, err)
+
+	// Decode.
+	extractDir := t.TempDir()
+	desc := ocispec.Descriptor{}
+	require.NoError(t, c.Decode(extractDir, "data.bin", bytes.NewReader(tarData), desc))
+
+	got, err := os.ReadFile(filepath.Join(extractDir, "data.bin"))
+	require.NoError(t, err)
+	assert.Equal(t, content, got)
+}
+
+func TestTarInvalidArchive(t *testing.T) {
+	t.Parallel()
+	c := newTar()
+	extractDir := t.TempDir()
+	desc := ocispec.Descriptor{}
+
+	// Feed garbage data as a tar stream.
+	err := c.Decode(extractDir, "file.txt", strings.NewReader("this is not a tar"), desc)
+	assert.Error(t, err)
+}