Fix unit test and integration test for test_accept_block and SyncChurn

sync/src/relayer/tests/helper.rs

@@ -173,6 +173,10 @@ pub(crate) fn build_chain(tip: BlockNumber) -> (Relayer, OutPoint) {
 
     let chain_controller = start_chain_services(pack.take_chain_services_builder());
 
+    while chain_controller.is_verifying_unverified_blocks_on_startup() {
+        std::thread::sleep(std::time::Duration::from_millis(10));
+    }
+
     // Build 1 ~ (tip-1) heights
     for i in 0..tip {
         let parent = shared

test/src/specs/sync/sync_churn.rs

@@ -64,7 +64,9 @@ impl Spec for SyncChurn {
                 node.stop();
                 node.start();
             }
-            restart_stopped_tx.send(()).unwrap();
+            if let Err(err) = restart_stopped_tx.send(()) {
+                info!("Restart thread has exited already: {:?}", err);
+            }
         });
 
         mining_thread.join().unwrap();