--- a/dom/media/CubebUtils.cpp
+++ b/dom/media/CubebUtils.cpp
@@ -296,16 +296,25 @@ double GetVolumeScale()
 }
 
 cubeb* GetCubebContext()
 {
   StaticMutexAutoLock lock(sMutex);
   return GetCubebContextUnlocked();
 }
 
+// This is only exported when running tests.
+void
+ForceSetCubebContext(cubeb* aCubebContext)
+{
+  StaticMutexAutoLock lock(sMutex);
+  sCubebContext = aCubebContext;
+  sCubebState = CubebState::Initialized;
+}
+
 bool InitPreferredSampleRate()
 {
   StaticMutexAutoLock lock(sMutex);
   if (sPreferredSampleRate != 0) {
     return true;
   }
 #ifdef MOZ_WIDGET_ANDROID
   sPreferredSampleRate = AndroidGetAudioOutputSampleRate();

--- a/dom/media/CubebUtils.h
+++ b/dom/media/CubebUtils.h
@@ -49,12 +49,17 @@ void GetCurrentBackend(nsAString& aBacke
 void GetDeviceCollection(nsTArray<RefPtr<AudioDeviceInfo>>& aDeviceInfos,
                          Side aSide);
 cubeb_stream_prefs GetDefaultStreamPrefs();
 
 #ifdef MOZ_WIDGET_ANDROID
 uint32_t AndroidGetAudioOutputSampleRate();
 uint32_t AndroidGetAudioOutputFramesPerBuffer();
 #endif
+
+#ifdef ENABLE_SET_CUBEB_BACKEND
+void
+ForceSetCubebContext(cubeb* aCubebContext);
+#endif
 } // namespace CubebUtils
 } // namespace mozilla
 
 #endif // CubebUtils_h_