When testing microtask queues, make sure that
they're not automatically drained.

test/cctest/test_environment.cc

diff --git a/test/cctest/test_environment.cc b/test/cctest/test_environment.cc
index e293133..6abdd95 100644
--- a/test/cctest/test_environment.cc
+++ b/test/cctest/test_environment.cc
@@ -647,7 +647,8 @@
   const v8::HandleScope handle_scope(isolate_);
   const Argv argv;
 
-  std::unique_ptr<v8::MicrotaskQueue> queue = v8::MicrotaskQueue::New(isolate_);
+  std::unique_ptr<v8::MicrotaskQueue> queue = v8::MicrotaskQueue::New(
+      isolate_, v8::MicrotasksPolicy::kExplicit);
   v8::Local<v8::Context> context = v8::Context::New(
       isolate_, nullptr, {}, {}, {}, queue.get());
   node::InitializeContext(context);