add fust test for downloader

Signed-off-by: Adam Korczynski <adam@adalogics.com>

Author: AdamKorcz

pkg/downloader/fuzz_test.go

@@ -0,0 +1,35 @@
+package downloader
+
+import (
+	"context"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/opencontainers/go-digest"
+)
+
+var a = digest.Algorithm("sha256")
+
+func FuzzDownload(f *testing.F) {
+	f.Fuzz(func(t *testing.T, fileContents []byte, checkDigest bool) {
+		localFile := filepath.Join(t.TempDir(), "localFile")
+		remoteFile := filepath.Join(t.TempDir(), "remoteFile")
+		err := os.WriteFile(remoteFile, fileContents, 0o600)
+		if err != nil {
+			t.Fatal(err)
+		}
+		testLocalFileURL := "file://" + remoteFile
+		if checkDigest {
+			d := a.FromBytes(fileContents)
+			_, _ = Download(context.Background(),
+				localFile,
+				testLocalFileURL,
+				WithExpectedDigest(d))
+		} else {
+			_, _ = Download(context.Background(),
+				localFile,
+				testLocalFileURL)
+		}
+	})
+}