--- a/dom/workers/WorkerPrivate.cpp
+++ b/dom/workers/WorkerPrivate.cpp
@@ -2612,31 +2612,34 @@ WorkerPrivate::WorkerPrivate(WorkerPriva
   , mWorkerScriptExecutedSuccessfully(false)
   , mFetchHandlerWasAdded(false)
   , mOnLine(false)
   , mMainThreadObjectsForgotten(false)
   , mIsChromeWorker(aIsChromeWorker)
   , mParentFrozen(false)
   , mIsSecureContext(false)
   , mDebuggerRegistered(false)
+  , mIsInAutomation(false)
 {
   MOZ_ASSERT_IF(!IsDedicatedWorker(), NS_IsMainThread());
   mLoadInfo.StealFrom(aLoadInfo);
 
   if (aParent) {
     aParent->AssertIsOnWorkerThread();
 
     // Note that this copies our parent's secure context state into mJSSettings.
     aParent->CopyJSSettings(mJSSettings);
 
     // And manually set our mIsSecureContext, though it's not really relevant to
     // dedicated workers...
     mIsSecureContext = aParent->IsSecureContext();
     MOZ_ASSERT_IF(mIsChromeWorker, mIsSecureContext);
 
+    mIsInAutomation = aParent->IsInAutomation();
+
     MOZ_ASSERT(IsDedicatedWorker());
 
     if (aParent->mParentFrozen) {
       Freeze(nullptr);
     }
 
     mOnLine = aParent->OnLine();
   }
@@ -2660,16 +2663,18 @@ WorkerPrivate::WorkerPrivate(WorkerPriva
 
     if (mIsSecureContext) {
       mJSSettings.chrome.compartmentOptions
                  .creationOptions().setSecureContext(true);
       mJSSettings.content.compartmentOptions
                  .creationOptions().setSecureContext(true);
     }
 
+    mIsInAutomation = xpc::IsInAutomation();
+
     // Our parent can get suspended after it initiates the async creation
     // of a new worker thread.  In this case suspend the new worker as well.
     if (mLoadInfo.mWindow && mLoadInfo.mWindow->IsSuspended()) {
       ParentWindowPaused();
     }
 
     if (mLoadInfo.mWindow && mLoadInfo.mWindow->IsFrozen()) {
       Freeze(mLoadInfo.mWindow);

--- a/dom/workers/WorkerPrivate.h
+++ b/dom/workers/WorkerPrivate.h
@@ -628,16 +628,22 @@ public:
   // compartment of the worker global.  The only reason we don't
   // AssertIsOnParentThread() here is so we can assert that this value matches
   // the one on the compartment, which has to be done from the worker thread.
   bool IsSecureContext() const
   {
     return mIsSecureContext;
   }
 
+  // Check whether we're running in automation.
+  bool IsInAutomation() const
+  {
+    return mIsInAutomation;
+  }
+
   TimeStamp CreationTimeStamp() const
   {
     return mCreationTimeStamp;
   }
 
   DOMHighResTimeStamp CreationTime() const
   {
     return mCreationTimeHighRes;
@@ -1474,16 +1480,20 @@ private:
   // of state (loadinfo, worker type, parent).
   //
   // It's a bit unfortunate that we have to have an out-of-band boolean for
   // this, but we need access to this state from the parent thread, and we can't
   // use our global object's secure state there.
   bool mIsSecureContext;
 
   bool mDebuggerRegistered;
+
+  // mIsInAutomation is true when we're running in test automation.
+  // We expose some extra testing functions in that case.
+  bool mIsInAutomation;
 };
 
 class AutoSyncLoopHolder
 {
   WorkerPrivate* mWorkerPrivate;
   nsCOMPtr<nsIEventTarget> mTarget;
   uint32_t mIndex;