this fixes the last test somehow

packages/svelte/src/internal/client/reactivity/batch.js

@@ -472,12 +472,15 @@ export function flushSync(fn) {
 					batch.flush();
 				}
 
+				// TODO this feels wrong
+				if (queued_root_effects.length === 0) {
 					// this would be reset in `batch.flush_effects()` but since we are early returning here,
 					// we need to reset it here as well in case the first time there's 0 queued root effects
 					last_scheduled_effect = null;
 
 					return /** @type {T} */ (result);
 				}
+			}
 
 			batch.flush_effects();
 		}