1 files changed, 53 insertions, 0 deletions
diff --git a/xpcom/tests/gtest/TestThreads_mac.mm b/xpcom/tests/gtest/TestThreads_mac.mm
new file mode 100644
index 0000000000..c221452684
--- /dev/null
+++ b/xpcom/tests/gtest/TestThreads_mac.mm
@@ -0,0 +1,53 @@
+/* -*- 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 <Foundation/Foundation.h>
+
+#include "gtest/gtest.h"
+#include "mozilla/SyncRunnable.h"
+#include "nsIThread.h"
+#include "nsIThreadManager.h"
+
+using namespace mozilla;
+
+// Tests whether an nsThread ran a block in its NSRunLoop.
+// ThreadCreationOptions.isUiThread gets set to aIsUiThread.
+// Returns true if a block ran on the NSRunLoop.
+bool UiThreadRunsRunLoop(bool aIsUiThread) {
+  nsCOMPtr<nsIThread> thread;
+  nsIThreadManager::ThreadCreationOptions options;
+  options.isUiThread = aIsUiThread;
+  MOZ_ALWAYS_SUCCEEDS(
+      NS_NewNamedThread("Testing Thread", getter_AddRefs(thread), nullptr, options));
+
+  __block bool blockRanInRunLoop = false;
+  {
+    // We scope this so `loop` doesn't live past `thread-Shutdown()` since this file is compiled
+    // without ARC.
+    NSRunLoop* loop = nil;
+    auto syncRunnable = MakeRefPtr<SyncRunnable>(NS_NewRunnableFunction(__func__, [&] {
+      // If the thread doesn't already have an NSRunLoop, one will be created.
+      loop = NSRunLoop.currentRunLoop;
+    }));
+    MOZ_ALWAYS_SUCCEEDS(syncRunnable->DispatchToThread(thread));
+
+    [loop performBlock:^void() {
+      blockRanInRunLoop = true;
+    }];
+  }
+
+  thread->Shutdown();
+  return blockRanInRunLoop;
+}
+
+TEST(ThreadsMac, OptionsIsUiThread)
+{
+  const bool isUiThread = true;
+  const bool isNoUiThread = false;
+
+  EXPECT_TRUE(UiThreadRunsRunLoop(isUiThread));
+  EXPECT_FALSE(UiThreadRunsRunLoop(isNoUiThread));
+}