onSnapshot should call immediatly and then after data changes.

Author: BrianChapman

src/firestore-query.js

@@ -170,6 +170,10 @@ MockFirestoreQuery.prototype.onSnapshot = function (optionsOrObserverOrOnNext, o
       onError(err);
     }
   };
+
+  // onSnapshot should always return when initially called, then
+  // every time data changes.
+  onSnapshot();
   var unsubscribe = this.queue.onPostFlush(onSnapshot);
 
   // return the unsubscribe function

test/unit/firestore-collection.js

@@ -406,9 +406,16 @@ describe('MockFirestoreCollection', function () {
     it('Calls onError if error', function (done) {
       var error = new Error("An error occured.");
       collection.errs.onSnapshot = error;
+      var callCount = 0;
       collection.onSnapshot(function(snap) {
         throw new Error("This should not be called.");
       }, function(err) {
+        // onSnapshot always returns when first called and then
+        // after data changes so we get 2 calls here.
+        if (callCount == 0) {
+          callCount++;
+          return;
+        }
         expect(err).to.equal(error);
         done();
       });