diff -r 000000000000 -r 6474c204b198 gfx/tests/gtest/TestGfxPrefs.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gfx/tests/gtest/TestGfxPrefs.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,67 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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 http://mozilla.org/MPL/2.0/. */
+
+#include "gtest/gtest.h"
+
+#include "gfxPrefs.h"
+#ifdef GFX_DECL_PREF
+#error "This is not supposed to be defined outside of gfxPrefs.h"
+#endif
+
+// If the default values for any of these preferences change,
+// just modify the test to match. We are only testing against
+// a particular value to make sure we receive the correct
+// result through this API.
+
+TEST(GfxPrefs, Singleton) {
+  ASSERT_FALSE(gfxPrefs::SingletonExists());
+  gfxPrefs::GetSingleton();
+  ASSERT_TRUE(gfxPrefs::SingletonExists());
+  gfxPrefs::DestroySingleton();
+  ASSERT_FALSE(gfxPrefs::SingletonExists());
+}
+
+TEST(GfxPrefs, LiveValues) {
+  ASSERT_FALSE(gfxPrefs::SingletonExists());
+  gfxPrefs::GetSingleton();
+  ASSERT_TRUE(gfxPrefs::SingletonExists());
+
+  // Live boolean, default false
+  ASSERT_FALSE(gfxPrefs::CanvasAzureAccelerated());
+
+  // Live int32_t, default 23456
+  ASSERT_TRUE(gfxPrefs::LayerScopePort() == 23456);
+
+  // Live uint32_t, default 2
+  ASSERT_TRUE(gfxPrefs::MSAALevel() == 2);
+
+  gfxPrefs::DestroySingleton();
+  ASSERT_FALSE(gfxPrefs::SingletonExists());
+}
+
+TEST(GfxPrefs, OnceValues) {
+  ASSERT_FALSE(gfxPrefs::SingletonExists());
+  gfxPrefs::GetSingleton();
+  ASSERT_TRUE(gfxPrefs::SingletonExists());
+
+  // Once boolean, default true
+  ASSERT_TRUE(gfxPrefs::WorkAroundDriverBugs());
+
+  // Once boolean, default false
+  ASSERT_FALSE(gfxPrefs::LayersDump());
+
+  // Once int32_t, default 95
+  ASSERT_TRUE(gfxPrefs::CanvasSkiaGLCacheSize() == 96);
+
+  // Once uint32_t, default 5
+  ASSERT_TRUE(gfxPrefs::APZMaxVelocityQueueSize() == 5);
+
+  // Once float, default -1 (should be OK with ==)
+  ASSERT_TRUE(gfxPrefs::APZMaxVelocity() == -1.0f);
+
+  gfxPrefs::DestroySingleton();
+  ASSERT_FALSE(gfxPrefs::SingletonExists());
+}
+