1 files changed, 22 insertions, 0 deletions
diff --git a/test/sandbox/testdata/sum.go b/test/sandbox/testdata/sum.go
new file mode 100644
index 00000000..e4e8643a
--- /dev/null
+++ b/test/sandbox/testdata/sum.go
@@ -0,0 +1,22 @@
+//go:build testsuite || tester
+
+package testdata
+
+import (
+	"crypto/sha512"
+	"encoding/base64"
+	"strconv"
+)
+
+// sum decodes s as [base64.StdEncoding] and panics if it is invalid or
+// unexpectedly sized.
+func sum(s string) [sha512.Size]byte {
+	p, err := base64.StdEncoding.DecodeString(s)
+	if err != nil {
+		panic(err)
+	}
+	if len(p) != sha512.Size {
+		panic("unexpected checksum sized " + strconv.Itoa(len(p)))
+	}
+	return ([sha512.Size]byte)(p)
+}