Add tests

cache/disk/casblob/BUILD.bazel

@@ -11,4 +11,9 @@ go_library(
 go_test(
     name = "go_default_test",
     srcs = ["casblob_test.go"],
+    deps = [
+        ":go_default_library",
+        "//cache/disk/zstdimpl:go_default_library",
+        "//utils:go_default_library",
+    ],
 )

cache/disk/casblob/casblob_test.go

@@ -1,8 +1,18 @@
 package casblob_test
 
 import (
+	"bytes"
+	"crypto/sha256"
+	"encoding/hex"
+	"fmt"
+	"io"
+	"os"
 	"testing"
 	"unsafe"
+
+	"github.com/buchgr/bazel-remote/v2/cache/disk/casblob"
+	"github.com/buchgr/bazel-remote/v2/cache/disk/zstdimpl"
+	testutils "github.com/buchgr/bazel-remote/v2/utils"
 )
 
 func TestLenSize(t *testing.T) {
@@ -17,3 +27,55 @@ func TestLenSize(t *testing.T) {
 		t.Errorf("This should silence linters that think slice is never used")
 	}
 }
+
+func TestZstdFromLegacy(t *testing.T) {
+	size := 1024
+	zstd, err := zstdimpl.Get("go")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	data, hash := testutils.RandomDataAndHash(int64(size))
+	dir := testutils.TempDir(t)
+	filename := fmt.Sprintf("%s/%s", dir, hash)
+	file, err := os.OpenFile(filename, os.O_RDWR|os.O_CREATE|os.O_EXCL, 0664)
+	if err != nil {
+		t.Fatal(err)
+	}
+	n, err := file.Write(data)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if n != size {
+		t.Fatalf("Unexpected short write %d, expected %d", n, size)
+	}
+	file.Close()
+
+	file, err = os.Open(filename)
+	if err != nil {
+		t.Fatal(err)
+	}
+	zrc, err := casblob.GetLegacyZstdReadCloser(zstd, file)
+	if err != nil {
+		t.Fatal(err)
+	}
+	rc, err := zstd.GetDecoder(zrc)
+	if err != nil {
+		t.Fatal(err)
+	}
+	buf := bytes.NewBuffer(nil)
+	_, err = io.Copy(buf, rc)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if buf.Len() != size {
+		t.Fatalf("Unexpected buf size %d, expected %d", buf.Len(), size)
+	}
+
+	h := sha256.Sum256(data)
+	hs := hex.EncodeToString(h[:])
+	if hs != hash {
+		t.Fatalf("Unexpected content sha %s, expected %s", hs, hash)
+	}
+}