[test] Add tests for _get_empty() funcs
diff --git a/test/test-blob.c b/test/test-blob.c
index 22d40b7..beb23a5 100644
--- a/test/test-blob.c
+++ b/test/test-blob.c
@@ -52,6 +52,7 @@
 
   g_assert (hb_blob_is_immutable (hb_blob_get_empty ()));
   g_assert (hb_blob_get_empty () != NULL);
+  g_assert (hb_blob_get_empty () == hb_blob_create (NULL, 0, HB_MEMORY_MODE_READONLY, NULL, NULL));
 
   blob = hb_blob_get_empty ();
   g_assert (blob == hb_blob_get_empty ());