diff --git a/testing/fxgc_unittest.cpp b/testing/fxgc_unittest.cpp
index 0e467cf..538565e 100644
--- a/testing/fxgc_unittest.cpp
+++ b/testing/fxgc_unittest.cpp
@@ -14,12 +14,18 @@
 
 void FXGCUnitTest::SetUp() {
   FXV8UnitTest::SetUp();
-  FXGC_Initialize(V8TestEnvironment::GetInstance()->platform(), nullptr);
+  auto* env = V8TestEnvironment::GetInstance();
+  FXGC_Initialize(env->platform(), env->isolate());
   heap_ = FXGC_CreateHeap();
   ASSERT_TRUE(heap_);
 }
 
 void FXGCUnitTest::TearDown() {
+  FXGC_ForceGarbageCollection(heap_.get());
+  auto* env = V8TestEnvironment::GetInstance();
+  while (v8::platform::PumpMessageLoop(env->platform(), env->isolate()))
+    continue;
+
   heap_.reset();
   FXGC_Release();
   FXV8UnitTest::TearDown();