[macOS] Clean up resources in ViewController tests

shell/platform/darwin/macos/framework/Source/FlutterEngineTestUtils.h

@@ -5,6 +5,8 @@
 #import "flutter/shell/platform/darwin/macos/framework/Headers/FlutterEngine.h"
 
 #import <OCMock/OCMock.h>
+
+#include "flutter/testing/autoreleasepool_test.h"
 #include "flutter/testing/test_dart_native_resolver.h"
 #include "gtest/gtest.h"
 
@@ -36,6 +38,30 @@ class FlutterEngineTest : public ::testing::Test {
 
 // Returns a mock FlutterEngine that is able to work in environments
 // without a real pasteboard.
+//
+// Callers MUST call [mockEngine shutDownEngine] when finished with the returned engine.
 id CreateMockFlutterEngine(NSString* pasteboardString);
 
+class MockFlutterEngineTest : public AutoreleasePoolTest {
+ public:
+  MockFlutterEngineTest();
+
+  void SetUp() override;
+  void TearDown() override;
+
+  id GetMockEngine() { return engine_mock_; }
+
+  void ShutDownEngine();
+
+  ~MockFlutterEngineTest() {
+    [engine_mock_ shutDownEngine];
+    [engine_mock_ stopMocking];
+  }
+
+ private:
+  id engine_mock_;
+
+  FML_DISALLOW_COPY_AND_ASSIGN(MockFlutterEngineTest);
+};
+
 }  // namespace flutter::testing

shell/platform/darwin/macos/framework/Source/FlutterEngineTestUtils.mm

@@ -67,4 +67,21 @@ id CreateMockFlutterEngine(NSString* pasteboardString) {
   }
 }
 
+MockFlutterEngineTest::MockFlutterEngineTest() = default;
+
+void MockFlutterEngineTest::SetUp() {
+  engine_mock_ = CreateMockFlutterEngine(@"");
+}
+
+void MockFlutterEngineTest::TearDown() {
+  [engine_mock_ shutDownEngine];
+  [engine_mock_ stopMocking];
+  engine_mock_ = nil;
+}
+
+void MockFlutterEngineTest::ShutDownEngine() {
+  [engine_mock_ shutDownEngine];
+  engine_mock_ = nil;
+}
+
 }  // namespace flutter::testing