--- a/toolkit/components/places/PlacesUtils.jsm
+++ b/toolkit/components/places/PlacesUtils.jsm
@@ -2544,18 +2544,23 @@ var GuidHelper = {
   },
 
   invalidateCacheForItemId(aItemId) {
     let guid = this.guidsForIds.get(aItemId);
     this.guidsForIds.delete(aItemId);
     this.idsForGuids.delete(guid);
   },
 
+  invalidateCache() {
+    this.guidsForIds.clear();
+    this.idsForGuids.clear();
+  },
+
   ensureObservingRemovedItems() {
-    if (!("observer" in this)) {
+    if (!this.observer) {
       /**
        * This observers serves two purposes:
        * (1) Invalidate cached id<->GUID paris on when items are removed.
        * (2) Cache GUIDs given us free of charge by onItemAdded/onItemRemoved.
       *      So, for exmaple, when the NewBookmark needs the new GUID, we already
       *      have it cached.
       */
       this.observer = {
@@ -2577,16 +2582,21 @@ var GuidHelper = {
         onEndUpdateBatch() {},
         onItemChanged() {},
         onItemVisited() {},
         onItemMoved() {},
       };
       PlacesUtils.bookmarks.addObserver(this.observer, false);
       PlacesUtils.registerShutdownFunction(() => {
         PlacesUtils.bookmarks.removeObserver(this.observer);
+        if (PlacesUtils._isDBTestingEnabled()) {
+          // Invalidate the entire cache if we expect to restart the database.
+          this.invalidateCache();
+          this.observer = null;
+        }
       });
     }
   }
 };
 
 // Transactions handlers.
 
 /**

--- a/toolkit/components/places/nsNavBookmarks.cpp
+++ b/toolkit/components/places/nsNavBookmarks.cpp
@@ -3360,27 +3360,30 @@ nsNavBookmarks::NotifyItemChanged(const 
 //// nsIObserver
 
 NS_IMETHODIMP
 nsNavBookmarks::Observe(nsISupports *aSubject, const char *aTopic,
                         const char16_t *aData)
 {
   NS_ASSERTION(NS_IsMainThread(), "This can only be called on the main thread");
 
-  if (strcmp(aTopic, TOPIC_PLACES_SHUTDOWN) == 0) {
-    // Stop Observing annotations.
+  ReadTestingEnabled();
+  if (strcmp(aTopic, TOPIC_PLACES_SHUTDOWN) == 0 && !mTestingEnabled) {
+    // Stop Observing annotations if we don't expect to restart the database.
     nsAnnotationService* annosvc = nsAnnotationService::GetAnnotationService();
     if (annosvc) {
       annosvc->RemoveObserver(this);
     }
   }
   else if (strcmp(aTopic, TOPIC_PLACES_CONNECTION_CLOSED) == 0) {
     // Don't even try to notify observers from this point on, the category
     // cache would init services that could try to use our APIs.
-    mCanNotify = false;
+    if (!mTestingEnabled) {
+      mCanNotify = false;
+    }
     mObservers.Clear();
   }
 
   return NS_OK;
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 //// nsINavHistoryObserver

--- a/toolkit/components/places/nsNavHistory.cpp
+++ b/toolkit/components/places/nsNavHistory.cpp
@@ -3084,17 +3084,20 @@ nsNavHistory::Observe(nsISupports *aSubj
     RefPtr<Database> DB = GetDatabase();
     NS_ENSURE_STATE(DB);
     DB->Observe(aSubject, aTopic, aData);
   }
 
   else if (strcmp(aTopic, TOPIC_PLACES_CONNECTION_CLOSED) == 0) {
     // Don't even try to notify observers from this point on, the category
     // cache would init services that could try to use our APIs.
-    mCanNotify = false;
+    ReadTestingEnabled();
+    if (!mTestingEnabled) {
+      mCanNotify = false;
+    }
     mObservers.Clear();
   }
 
 #ifdef MOZ_XUL
   else if (strcmp(aTopic, TOPIC_AUTOCOMPLETE_FEEDBACK_INCOMING) == 0) {
     nsCOMPtr<nsIAutoCompleteInput> input = do_QueryInterface(aSubject);
     if (!input)
       return NS_OK;