Update declarer.dart

pkgs/test_api/lib/src/backend/declarer.dart

diff --git a/pkgs/test_api/lib/src/backend/declarer.dart b/pkgs/test_api/lib/src/backend/declarer.dart
index 56f107e..658eb3f 100644
--- a/pkgs/test_api/lib/src/backend/declarer.dart
+++ b/pkgs/test_api/lib/src/backend/declarer.dart
@@ -312,7 +312,9 @@
   /// Registers a function to be called after all tests in the test library are completed.
   void addTearDownLibrary(dynamic Function() callback) {
     var declarer = this;
-    while (declarer._parent != null) declarer = declarer._parent!;
+    while (declarer._parent != null) {
+      declarer = declarer._parent!;
+    }
     declarer.addTearDownAll(callback);
   }