--- a/dom/media/CubebUtils.cpp
+++ b/dom/media/CubebUtils.cpp
@@ -35,16 +35,18 @@
 #define PREF_VOLUME_SCALE "media.volume_scale"
 #define PREF_CUBEB_BACKEND "media.cubeb.backend"
 #define PREF_CUBEB_LATENCY_PLAYBACK "media.cubeb_latency_playback_ms"
 #define PREF_CUBEB_LATENCY_MSG "media.cubeb_latency_msg_frames"
 // Allows to get something non-default for the preferred sample-rate, to allow
 // troubleshooting in the field and testing.
 #define PREF_CUBEB_FORCE_SAMPLE_RATE "media.cubeb.force_sample_rate"
 #define PREF_CUBEB_LOGGING_LEVEL "media.cubeb.logging_level"
+// Hidden pref used by tests to force failure to obtain cubeb context
+#define PREF_CUBEB_FORCE_NULL_CONTEXT "media.cubeb.force_null_context"
 #define PREF_CUBEB_SANDBOX "media.cubeb.sandbox"
 #define PREF_AUDIOIPC_POOL_SIZE "media.audioipc.pool_size"
 #define PREF_AUDIOIPC_STACK_SIZE "media.audioipc.stack_size"
 
 #if (defined(XP_LINUX) && !defined(MOZ_WIDGET_ANDROID)) || defined(XP_MACOSX)
 #define MOZ_CUBEB_REMOTING
 #endif
 
@@ -122,16 +124,17 @@ uint32_t sCubebPlaybackLatencyInMillisec
 uint32_t sCubebMSGLatencyInFrames = 512;
 // If sCubebForcedSampleRate is zero, PreferredSampleRate will return the
 // preferred sample-rate for the audio backend in use. Otherwise, it will be
 // used as the preferred sample-rate.
 uint32_t sCubebForcedSampleRate = 0;
 bool sCubebPlaybackLatencyPrefSet = false;
 bool sCubebMSGLatencyPrefSet = false;
 bool sAudioStreamInitEverSucceeded = false;
+bool sCubebForceNullContext = false;
 #ifdef MOZ_CUBEB_REMOTING
 bool sCubebSandbox = false;
 size_t sAudioIPCPoolSize;
 size_t sAudioIPCStackSize;
 #endif
 StaticAutoPtr<char> sBrandName;
 StaticAutoPtr<char> sCubebBackendName;
 
@@ -230,16 +233,21 @@ void PrefChanged(const char* aPref, void
     Preferences::GetCString(aPref, value);
     if (value.IsEmpty()) {
       sCubebBackendName = nullptr;
     } else {
       sCubebBackendName = new char[value.Length() + 1];
       PodCopy(sCubebBackendName.get(), value.get(), value.Length());
       sCubebBackendName[value.Length()] = 0;
     }
+  } else if (strcmp(aPref, PREF_CUBEB_FORCE_NULL_CONTEXT) == 0) {
+    StaticMutexAutoLock lock(sMutex);
+    sCubebForceNullContext = Preferences::GetBool(aPref, false);
+    MOZ_LOG(gCubebLog, LogLevel::Verbose,
+            ("%s: %s", PREF_CUBEB_FORCE_NULL_CONTEXT, sCubebForceNullContext ? "true" : "false"));
   }
 #ifdef MOZ_CUBEB_REMOTING
   else if (strcmp(aPref, PREF_CUBEB_SANDBOX) == 0) {
     StaticMutexAutoLock lock(sMutex);
     sCubebSandbox = Preferences::GetBool(aPref);
     MOZ_LOG(gCubebLog, LogLevel::Verbose, ("%s: %s", PREF_CUBEB_SANDBOX, sCubebSandbox ? "true" : "false"));
 
     if (sCubebSandbox && !sServerHandle && XRE_IsParentProcess()) {
@@ -372,16 +380,22 @@ ipc::FileDescriptor CreateAudioIPCConnec
 #else
   return ipc::FileDescriptor();
 #endif
 }
 
 cubeb* GetCubebContextUnlocked()
 {
   sMutex.AssertCurrentThreadOwns();
+  if (sCubebForceNullContext) {
+    // Pref set such that we should return a null context
+    MOZ_LOG(gCubebLog, LogLevel::Debug,
+            ("%s: returning null context due to %s!", __func__, PREF_CUBEB_FORCE_NULL_CONTEXT));
+    return nullptr;
+  }
   if (sCubebState != CubebState::Uninitialized) {
     // If we have already passed the initialization point (below), just return
     // the current context, which may be null (e.g., after error or shutdown.)
     return sCubebContext;
   }
 
   if (!sBrandName && NS_IsMainThread()) {
     InitBrandName();
@@ -502,16 +516,17 @@ uint32_t GetCubebMSGLatencyInFrames(cube
 
 void InitLibrary()
 {
   Preferences::RegisterCallbackAndCall(PrefChanged, PREF_VOLUME_SCALE);
   Preferences::RegisterCallbackAndCall(PrefChanged, PREF_CUBEB_LATENCY_PLAYBACK);
   Preferences::RegisterCallbackAndCall(PrefChanged, PREF_CUBEB_LATENCY_MSG);
   Preferences::RegisterCallback(PrefChanged, PREF_CUBEB_FORCE_SAMPLE_RATE);
   Preferences::RegisterCallbackAndCall(PrefChanged, PREF_CUBEB_BACKEND);
+  Preferences::RegisterCallbackAndCall(PrefChanged, PREF_CUBEB_FORCE_NULL_CONTEXT);
   Preferences::RegisterCallbackAndCall(PrefChanged, PREF_CUBEB_SANDBOX);
   Preferences::RegisterCallbackAndCall(PrefChanged, PREF_AUDIOIPC_POOL_SIZE);
   Preferences::RegisterCallbackAndCall(PrefChanged, PREF_AUDIOIPC_STACK_SIZE);
   if (MOZ_LOG_TEST(gCubebLog, LogLevel::Verbose)) {
     cubeb_set_log_callback(CUBEB_LOG_VERBOSE, CubebLogCallback);
   } else if (MOZ_LOG_TEST(gCubebLog, LogLevel::Error)) {
     cubeb_set_log_callback(CUBEB_LOG_NORMAL, CubebLogCallback);
   }
@@ -537,16 +552,17 @@ void ShutdownLibrary()
   Preferences::UnregisterCallback(PrefChanged, PREF_AUDIOIPC_STACK_SIZE);
   Preferences::UnregisterCallback(PrefChanged, PREF_AUDIOIPC_POOL_SIZE);
   Preferences::UnregisterCallback(PrefChanged, PREF_CUBEB_SANDBOX);
   Preferences::UnregisterCallback(PrefChanged, PREF_CUBEB_BACKEND);
   Preferences::UnregisterCallback(PrefChanged, PREF_CUBEB_LATENCY_PLAYBACK);
   Preferences::UnregisterCallback(PrefChanged, PREF_CUBEB_FORCE_SAMPLE_RATE);
   Preferences::UnregisterCallback(PrefChanged, PREF_CUBEB_LATENCY_MSG);
   Preferences::UnregisterCallback(PrefChanged, PREF_CUBEB_LOGGING_LEVEL);
+  Preferences::UnregisterCallback(PrefChanged, PREF_CUBEB_FORCE_NULL_CONTEXT);
 
   StaticMutexAutoLock lock(sMutex);
   if (sCubebContext) {
     cubeb_destroy(sCubebContext);
     sCubebContext = nullptr;
   }
   sBrandName = nullptr;
   sCubebBackendName = nullptr;