1 files changed, 121 insertions, 0 deletions
diff --git a/xpcom/tests/gtest/TestStateMirroring.cpp b/xpcom/tests/gtest/TestStateMirroring.cpp
new file mode 100644
index 0000000000..e96ecb9a18
--- /dev/null
+++ b/xpcom/tests/gtest/TestStateMirroring.cpp
@@ -0,0 +1,121 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#include "gtest/gtest.h"
+#include "mozilla/gtest/WaitFor.h"
+#include "mozilla/SharedThreadPool.h"
+#include "mozilla/StateMirroring.h"
+#include "mozilla/SynchronizedEventQueue.h"
+#include "mozilla/TaskQueue.h"
+#include "mozilla/Unused.h"
+#include "nsISupportsImpl.h"
+#include "nsThreadUtils.h"
+#include "VideoUtils.h"
+
+namespace TestStateMirroring {
+
+using namespace mozilla;
+
+class StateMirroringTest : public ::testing::Test {
+ public:
+  using ValueType = int;
+  using Promise = MozPromise<ValueType, bool, /*IsExclusive =*/true>;
+
+  StateMirroringTest()
+      : mTarget(
+            TaskQueue::Create(GetMediaThreadPool(MediaThreadType::SUPERVISOR),
+                              "TestStateMirroring",
+                              /*aSupportsTailDispatch =*/true)),
+        mCanonical(AbstractThread::GetCurrent(), 0, "TestCanonical"),
+        mMirror(mTarget, 0, "TestMirror") {}
+
+  void TearDown() override {
+    mTarget->BeginShutdown();
+    mTarget->AwaitShutdownAndIdle();
+
+    // Make sure to run any events just dispatched from mTarget to main thread
+    // before continuing on to the next test.
+    NS_ProcessPendingEvents(nullptr);
+  }
+
+  RefPtr<Promise> ReadMirrorAsync() {
+    return InvokeAsync(mTarget, __func__, [&] {
+      return Promise::CreateAndResolve(mMirror, "ReadMirrorAsync::Resolve");
+    });
+  }
+
+ protected:
+  const RefPtr<TaskQueue> mTarget;
+  Canonical<int> mCanonical;
+  Mirror<int> mMirror;
+};
+
+TEST_F(StateMirroringTest, MirrorInitiatedEventOrdering) {
+  // Note that this requires the tail dispatcher, which is not available until
+  // we are processing events.
+  ASSERT_FALSE(AbstractThread::GetCurrent()->IsTailDispatcherAvailable());
+
+  MOZ_ALWAYS_SUCCEEDS(NS_DispatchAndSpinEventLoopUntilComplete(
+      "NeedTailDispatcher"_ns, GetCurrentSerialEventTarget(),
+      NS_NewRunnableFunction(__func__, [&] {
+        ASSERT_TRUE(AbstractThread::GetCurrent()->IsTailDispatcherAvailable());
+
+        RefPtr<Promise> mirrorPromise;
+
+        // This will ensure the tail dispatcher fires to dispatch the group
+        // runnable holding the Mirror::Connect task, before we continue the
+        // test.
+        MOZ_ALWAYS_SUCCEEDS(NS_DispatchAndSpinEventLoopUntilComplete(
+            "NeedTailDispatcher"_ns, GetCurrentSerialEventTarget(),
+            NS_NewRunnableFunction(__func__, [&] {
+              // Show that mirroring does not take effect until async init is
+              // done.
+
+              MOZ_ALWAYS_SUCCEEDS(mTarget->Dispatch(NS_NewRunnableFunction(
+                  __func__, [&] { mMirror.Connect(&mCanonical); })));
+              mCanonical = 1;
+              mirrorPromise = ReadMirrorAsync();
+            })));
+
+        // Make sure Mirror::Connect has run on mTarget.
+        mTarget->AwaitIdle();
+
+        // Make sure Canonical::AddMirror has run on this thread.
+        NS_ProcessPendingEvents(nullptr);
+
+        // Prior to establishing the connection, a value has not been mirrored.
+        EXPECT_EQ(WaitFor(mirrorPromise).unwrap(), 0);
+
+        // Once a connection has been establised, event ordering is as expected.
+        mCanonical = 2;
+        EXPECT_EQ(WaitFor(ReadMirrorAsync()).unwrap(), 2);
+
+        MOZ_ALWAYS_SUCCEEDS(mTarget->Dispatch(NS_NewRunnableFunction(
+            __func__, [&] { mMirror.DisconnectIfConnected(); })));
+      })));
+}
+
+TEST_F(StateMirroringTest, CanonicalInitiatedEventOrdering) {
+  // Note that this requires the tail dispatcher, which is not available until
+  // we are processing events.
+  ASSERT_FALSE(AbstractThread::GetCurrent()->IsTailDispatcherAvailable());
+
+  MOZ_ALWAYS_SUCCEEDS(NS_DispatchAndSpinEventLoopUntilComplete(
+      "NeedTailDispatcher"_ns, GetCurrentSerialEventTarget(),
+      NS_NewRunnableFunction(__func__, [&] {
+        ASSERT_TRUE(AbstractThread::GetCurrent()->IsTailDispatcherAvailable());
+
+        mCanonical.ConnectMirror(&mMirror);
+
+        // Event ordering is as expected immediately.
+        mCanonical = 1;
+        EXPECT_EQ(WaitFor(ReadMirrorAsync()).unwrap(), 1);
+
+        mCanonical.DisconnectAll();
+      })));
+}
+
+}  // namespace TestStateMirroring