diff --git a/admin/spark-standalone.sh b/admin/spark-standalone.sh
index 2b38d4a5a3..e84c3bdbd0 100755
--- a/admin/spark-standalone.sh
+++ b/admin/spark-standalone.sh
@@ -9,6 +9,7 @@ PACKAGES_DIR=`dirname $0`/../packages
 echo 'Meteor = {};'
 cat $PACKAGES_DIR/uuid/uuid.js
 cat $PACKAGES_DIR/deps/deps.js
+cat $PACKAGES_DIR/deps/deps-utils.js
 cat $PACKAGES_DIR/liverange/liverange.js
 cat $PACKAGES_DIR/universal-events/listener.js
 cat $PACKAGES_DIR/universal-events/events-ie.js
diff --git a/examples/other/template-demo/client/template-demo.js b/examples/other/template-demo/client/template-demo.js
index 2268e41455..92a490cafa 100644
--- a/examples/other/template-demo/client/template-demo.js
+++ b/examples/other/template-demo/client/template-demo.js
@@ -137,32 +137,6 @@ Template.timer.destroyed = function () {
 
 ///////////////////////////////////////////////////////////////////////////////
 
-// Run f(). Record its dependencies. Rerun it whenever the
-// dependencies change.
-//
-// Returns an object with a stop() method. Call stop() to stop the
-// rerunning.
-//
-// XXX this should go into Meteor core as Meteor.autorun
-var autorun = function (f) {
-  var ctx;
-  var slain = false;
-  var rerun = function () {
-    if (slain)
-      return;
-    ctx = new Meteor.deps.Context;
-    ctx.run(f);
-    ctx.onInvalidate(rerun);
-  };
-  rerun();
-  return {
-    stop: function () {
-      slain = true;
-      ctx.invalidate();
-    }
-  };
-};
-
 Template.d3Demo.left = function () {
   return { group: "left" };
 };
@@ -233,7 +207,7 @@ Template.circles.rendered = function () {
 
   if (! self.handle) {
     d3.select(self.node).append("rect");
-    self.handle = autorun(function () {
+    self.handle = Meteor._autorun(function () {
       var circle = d3.select(self.node).selectAll("circle")
         .data(Circles.find({group: data.group}).fetch(),
               function (d) { return d._id; });
diff --git a/packages/deps/deps-utils.js b/packages/deps/deps-utils.js
new file mode 100644
index 0000000000..569d2deadd
--- /dev/null
+++ b/packages/deps/deps-utils.js
@@ -0,0 +1,118 @@
+(function () {
+  // XXX Document, test, and remove the leading underscore from everything.
+
+  ////////// Meteor.deps._ContextSet
+
+  // Constructor for an empty _ContextSet.
+  //
+  // A _ContextSet is used to hold a set of Meteor.deps.Contexts that
+  // are to be invalidated at some future time.  If a Context in the
+  // set becomes invalidated for any reason, it's immediately removed
+  // from the set.
+  var _ContextSet = function () {
+    this._contextsById = {};
+  };
+
+  // Adds the Context `ctx` to this set if it is not already
+  // present.  Returns true if the context is new to this set.
+  _ContextSet.prototype.add = function (ctx) {
+    var self = this;
+    if (ctx && ! (ctx.id in self._contextsById)) {
+      self._contextsById[ctx.id] = ctx;
+      ctx.onInvalidate(function () {
+        delete self._contextsById[ctx.id];
+      });
+      return true;
+    }
+    return false;
+  };
+
+  // Adds the current Context to this set if there is one.  Returns
+  // true if there is a current Context and it's new to the set.
+  _ContextSet.prototype.addCurrentContext = function () {
+    var self = this;
+    var context = Meteor.deps.Context.current;
+    if (! context)
+      return false;
+    return self.add(context);
+  };
+
+  // Invalidate all Contexts in this set.  They will be removed
+  // from the set as a consequence.
+  _ContextSet.prototype.invalidateAll = function () {
+    var self = this;
+    for (var id in self._contextsById)
+      self._contextsById[id].invalidate();
+  };
+
+  // Returns true if there are no Contexts in this set.
+  _ContextSet.prototype.isEmpty = function () {
+    var self = this;
+    for(var id in self._contextsById)
+      return false;
+    return true;
+  };
+
+  Meteor.deps._ContextSet = _ContextSet;
+
+  ////////// Meteor._autorun
+
+  // Run f(). Record its dependencies. Rerun it whenever the
+  // dependencies change.
+  //
+  // Returns an object with a stop() method. Call stop() to stop the
+  // rerunning.  Also passes this object as an argument to f.
+  Meteor._autorun = function (f) {
+    var ctx;
+    var slain = false;
+    var handle = {
+      stop: function () {
+        slain = true;
+        ctx.invalidate();
+      }
+    };
+    var rerun = function () {
+      if (slain)
+        return;
+      ctx = new Meteor.deps.Context;
+      ctx.run(function () { f.call(this, handle); });
+      ctx.onInvalidate(rerun);
+    };
+    rerun();
+    return handle;
+  };
+
+  ////////// Meteor._atFlush
+
+  // Run 'f' at Meteor.flush()-time. If atFlush is called multiple times,
+  // we guarantee that the 'f's will run in the same order that
+  // atFlush was called on them.  If we are inside a Meteor.flush() already,
+  // f will be scheduled as part of the current flush().
+
+  var atFlushQueue = [];
+  var atFlushContext = null;
+  Meteor._atFlush = function (f) {
+    atFlushQueue.push(f);
+
+    if (! atFlushContext) {
+      atFlushContext = new Meteor.deps.Context;
+      atFlushContext.onInvalidate(function () {
+        var f;
+        while ((f = atFlushQueue.shift())) {
+          // Since atFlushContext is truthy, if f() calls atFlush
+          // reentrantly, it's guaranteed to append to atFlushQueue and
+          // not contruct a new atFlushContext.
+          try {
+            f();
+          } catch (e) {
+            Meteor._debug("Exception from Meteor._atFlush:", e);
+          }
+        }
+        atFlushContext = null;
+      });
+
+      atFlushContext.invalidate();
+    }
+  };
+
+})();
\ No newline at end of file
diff --git a/packages/deps/deps.js b/packages/deps/deps.js
index dc229ad960..f1cff70855 100644
--- a/packages/deps/deps.js
+++ b/packages/deps/deps.js
@@ -59,7 +59,11 @@
 
         _.each(pending, function (ctx) {
           _.each(ctx._callbacks, function (f) {
-            f(ctx); // XXX wrap in try?
+            try {
+              f(ctx);
+            } catch (e) {
+              Meteor._debug("Exception from Meteor.flush:", e);
+            }
           });
           delete ctx._callbacks; // maybe help the GC
         });
diff --git a/packages/deps/package.js b/packages/deps/package.js
index 9949cfdd73..f21ff22073 100644
--- a/packages/deps/package.js
+++ b/packages/deps/package.js
@@ -9,5 +9,5 @@ Package.on_use(function (api, where) {
   where = where || ['client', 'server'];
 
   api.use('underscore', where);
-  api.add_files('deps.js', where);
+  api.add_files(['deps.js', 'deps-utils.js'], where);
 });
diff --git a/packages/session/session.js b/packages/session/session.js
index df76d163eb..c55d5b39e5 100644
--- a/packages/session/session.js
+++ b/packages/session/session.js
@@ -1,31 +1,9 @@
 // XXX could use some tests
 
 Session = _.extend({}, {
-  keys: {},
-  key_deps: {}, // key -> context id -> context
-  key_value_deps: {}, // key -> value -> context id -> context
-
-  // XXX remove debugging method (or improve it, but anyway, don't
-  // ship it in production)
-  dump_state: function () {
-    var self = this;
-    console.log("=== Session state ===");
-    for (var key in self.key_deps) {
-      var ids = _.keys(self.key_deps[key]);
-      if (!ids.length)
-        continue;
-      console.log(key + ": " + _.reject(ids, function (x) {return x === "_once"}).join(' '));
-    }
-
-    for (var key in self.key_value_deps) {
-      for (var value in self.key_value_deps[key]) {
-        var ids = _.keys(self.key_value_deps[key][value]);
-        if (!ids.length)
-          continue;
-        console.log(key + "(" + value + "): " + _.reject(ids, function (x) {return x === "_once";}).join(' '));
-      }
-    }
-  },
+  keys: {}, // key -> value
+  keyDeps: {}, // key -> _ContextSet
+  keyValueDeps: {}, // key -> value -> _ContextSet
 
   set: function (key, value) {
     var self = this;
@@ -36,35 +14,26 @@ Session = _.extend({}, {
         value !== null && value !== undefined)
       throw new Error("Session.set: value can't be an object");
 
-    var old_value = self.keys[key];
-    if (value === old_value)
+    var oldValue = self.keys[key];
+    if (value === oldValue)
       return;
     self.keys[key] = value;
 
-    var invalidate = function (map) {
-      if (map)
-        for (var id in map)
-          map[id].invalidate();
+    var invalidateAll = function (cset) {
+      cset && cset.invalidateAll();
     };
 
-    self._ensureKey(key);
-    invalidate(self.key_deps[key]);
-    invalidate(self.key_value_deps[key][old_value]);
-    invalidate(self.key_value_deps[key][value]);
+    invalidateAll(self.keyDeps[key]);
+    if (self.keyValueDeps[key]) {
+      invalidateAll(self.keyValueDeps[key][oldValue]);
+      invalidateAll(self.keyValueDeps[key][value]);
+    }
   },
 
   get: function (key) {
     var self = this;
-    var context = Meteor.deps.Context.current;
     self._ensureKey(key);
-
-    if (context && !(context.id in self.key_deps[key])) {
-      self.key_deps[key][context.id] = context;
-      context.onInvalidate(function () {
-        delete self.key_deps[key][context.id];
-      });
-    }
-
+    self.keyDeps[key].addCurrentContext();
     return self.keys[key];
   },
 
@@ -75,24 +44,23 @@ Session = _.extend({}, {
     if (typeof value !== 'string' &&
         typeof value !== 'number' &&
         typeof value !== 'boolean' &&
-        value !== null && value !== undefined)
+        typeof value !== 'undefined' &&
+        value !== null)
       throw new Error("Session.equals: value can't be an object");
 
     if (context) {
       self._ensureKey(key);
-      if (!(value in self.key_value_deps[key]))
-        self.key_value_deps[key][value] = {};
 
-      if (!(context.id in self.key_value_deps[key][value])) {
-        self.key_value_deps[key][value][context.id] = context;
+      if (!(value in self.keyValueDeps[key]))
+        self.keyValueDeps[key][value] = new Meteor.deps._ContextSet;
+
+      var isNew = self.keyValueDeps[key][value].add(context);
+      if (isNew) {
         context.onInvalidate(function () {
-          delete self.key_value_deps[key][value][context.id];
-
           // clean up [key][value] if it's now empty, so we don't use
           // O(n) memory for n = values seen ever
-          for (var x in self.key_value_deps[key][value])
-            return;
-          delete self.key_value_deps[key][value];
+          if (self.keyValueDeps[key][value].isEmpty())
+            delete self.keyValueDeps[key][value];
         });
       }
     }
@@ -102,9 +70,9 @@ Session = _.extend({}, {
 
   _ensureKey: function (key) {
     var self = this;
-    if (!(key in self.key_deps)) {
-      self.key_deps[key] = {};
-      self.key_value_deps[key] = {};
+    if (!(key in self.keyDeps)) {
+      self.keyDeps[key] = new Meteor.deps._ContextSet;
+      self.keyValueDeps[key] = {};
     }
   }
 });
diff --git a/packages/spark/spark.js b/packages/spark/spark.js
index 6706254e86..ee4d0b69be 100644
--- a/packages/spark/spark.js
+++ b/packages/spark/spark.js
@@ -22,7 +22,7 @@
 
 // XXX in landmark-demo, if Template.timer.created throws an exception,
 // then it is never called again, even if you push the 'create a
-// timer' button again. the problem is almost certainly in atFlushTime
+// timer' button again. the problem is almost certainly in atFlush
 // (not hard to see what it is.)
 
 (function() {
@@ -144,9 +144,19 @@ Spark._Renderer = function () {
 
 _.extend(Spark._Renderer.prototype, {
   // `what` can be a function that takes a LiveRange, or just a set of
-  // attributes to add to the liverange.  tag and what are optional.
-  // if no tag is passed, no liverange will be created.
-  annotate: function (html, type, what, unusedFunc) {
+  // attributes to add to the liverange.  type and what are optional.
+  // if no type is passed, no liverange will be created.
+  // If what is a function, it will be called no matter what, even
+  // if the annotated HTML was not used and no LiveRange was created,
+  // in which case it gets null as an argument.
+  annotate: function (html, type, what) {
+    if (typeof what !== 'function') {
+      var attribs = what;
+      what = function (range) {
+        if (range)
+          _.extend(range, attribs);
+      };
+    }
     // The annotation tags that we insert into HTML strings must be
     // unguessable in order to not create potential cross-site scripting
     // attack vectors, so we use random strings.  Even a well-written app
@@ -156,20 +166,15 @@ _.extend(Spark._Renderer.prototype, {
     // and not arbitrary user-entered data.
     var id = (type || '') + ":" + Spark._createId();
     this.annotations[id] = function (start, end) {
-      if (! start) {
-        // materialize called us with no args because this annotation
-        // wasn't used
-        unusedFunc && unusedFunc();
+      if ((! start) || (! type)) {
+        // ! start: materialize called us with no args because this
+        // annotation wasn't used
+        // ! type: no type given, don't generate a LiveRange
+        what(null);
         return;
       }
-      if (! type)
-        // no type given; don't generate a LiveRange
-        return;
       var range = makeRange(type, start, end);
-      if (what instanceof Function)
-        what(range);
-      else
-        _.extend(range, what);
+      what(range);
     };
 
     return "<$" + id + ">" + html + "</$" + id + ">";
@@ -340,8 +345,7 @@ var scheduleOnscreenSetup = function (frag, landmarkRanges) {
     finalized = true;
   };
 
-  var ctx = new Meteor.deps.Context;
-  ctx.onInvalidate(function () {
+  Meteor._atFlush(function () {
     if (finalized)
       return;
 
@@ -395,8 +399,6 @@ var scheduleOnscreenSetup = function (frag, landmarkRanges) {
     notifyWatchers(renderedRange.firstNode(), renderedRange.lastNode());
     renderedRange.destroy();
   });
-
-  ctx.invalidate();
 };
 
 Spark.render = function (htmlFunc) {
@@ -721,6 +723,9 @@ Spark.attachEvents = withRenderer(function (eventMap, html, _renderer) {
 
   html = _renderer.annotate(
     html, Spark._ANNOTATION_EVENTS, function (range) {
+      if (! range)
+        return;
+
       _.each(eventTypes, function (t) {
         listener.addType(t);
       });
@@ -787,66 +792,40 @@ Spark.isolate = function (htmlFunc) {
   if (!renderer)
     return htmlFunc();
 
-  var ctx = new Meteor.deps.Context;
-
-  return renderer.annotate(
-    ctx.run(htmlFunc), Spark._ANNOTATION_ISOLATE, function (range) {
-      range.finalize = function () {
-        // Spark.finalize() was called on us (presumably because we were
-        // removed from the document.) Tear down our structures without
-        // doing any more updates. note that range is about to be
-        // destroyed by finalize.
-        range = null;
-        ctx.invalidate();
-      };
-
-      var refresh = function () {
-        if (! range)
-          return; // killed by finalize. range has already been destroyed.
-
-        ctx = new Meteor.deps.Context;
-        Spark.renderToRange(range, function () {
-          return ctx.run(htmlFunc);
+  var range;
+  var firstRun = true;
+  var retHtml;
+  Meteor._autorun(function (handle) {
+    if (firstRun) {
+      retHtml = renderer.annotate(
+        htmlFunc(), Spark._ANNOTATION_ISOLATE,
+        function (r) {
+          if (! r) {
+            // annotation not used; kill our context
+            handle.stop();
+          } else {
+            range = r;
+            range.finalize = function () {
+              // Spark.finalize() was called on our range (presumably
+              // because it was removed from the document.)  Kill
+              // this context and stop rerunning.
+              handle.stop();
+            };
+          }
         });
-        ctx.onInvalidate(refresh);
-      };
+      firstRun = false;
+    } else {
+      Spark.renderToRange(range, htmlFunc);
+    }
+  });
 
-      ctx.onInvalidate(refresh);
-    });
+  return retHtml;
 };
 
 /******************************************************************************/
 /* Lists                                                                      */
 /******************************************************************************/
 
-// Run 'f' at flush()-time. If atFlushTime is called multiple times,
-// we guarantee that the 'f's will run in the order of their
-// respective atFlushTime calls.
-//
-// XXX either break this out into a separate package or fold it into
-// deps
-var atFlushQueue = [];
-var atFlushContext = null;
-var atFlushTime = function (f) {
-  atFlushQueue.push(f);
-
-  if (! atFlushContext) {
-    atFlushContext = new Meteor.deps.Context;
-    atFlushContext.onInvalidate(function () {
-      var f;
-      while ((f = atFlushQueue.shift())) {
-        // Since atFlushContext is truthy, if f() calls atFlushTime
-        // reentrantly, it's guaranteed to append to atFlushQueue and
-        // not contruct a new atFlushContext.
-        f();
-      }
-      atFlushContext = null;
-    });
-
-    atFlushContext.invalidate();
-  }
-};
-
 Spark.list = function (cursor, itemFunc, elseFunc) {
   elseFunc = elseFunc || function () { return ''; };
 
@@ -874,8 +853,8 @@ Spark.list = function (cursor, itemFunc, elseFunc) {
 
   // Get the renderer, if any
   var renderer = Spark._currentRenderer.get();
-  var annotate = renderer ?
-    _.bind(renderer.annotate, renderer) :
+  var maybeAnnotate = renderer ?
+        _.bind(renderer.annotate, renderer) :
     function (html) { return html; };
 
   // Render the initial contents. If we have a renderer, create a
@@ -889,11 +868,11 @@ Spark.list = function (cursor, itemFunc, elseFunc) {
   else {
     for (var i = 0; i < initialContents.length; i++) {
       (function (i) {
-        html += annotate(itemFunc(initialContents[i]),
-                         Spark._ANNOTATION_LIST_ITEM,
-                         function (range) {
-                           itemRanges[i] = range;
-                         });
+        html += maybeAnnotate(itemFunc(initialContents[i]),
+                              Spark._ANNOTATION_LIST_ITEM,
+                              function (range) {
+                                itemRanges[i] = range;
+                              });
       })(i); // scope i to closure
     }
   }
@@ -903,13 +882,15 @@ Spark.list = function (cursor, itemFunc, elseFunc) {
     handle.stop();
     stopped = true;
   };
-  html = annotate(html, Spark._ANNOTATION_LIST, function (range) {
-    outerRange = range;
-    outerRange.finalize = cleanup;
-  }, function () {
-    // We never ended up on the screen (caller discarded our return
-    // value)
-    cleanup();
+  html = maybeAnnotate(html, Spark._ANNOTATION_LIST, function (range) {
+    if (! range) {
+      // We never ended up on the screen (caller discarded our return
+      // value)
+      cleanup();
+    } else {
+      outerRange = range;
+      outerRange.finalize = cleanup;
+    }
   });
 
   // No renderer? Then we have no way to update the returned html and
@@ -930,7 +911,7 @@ Spark.list = function (cursor, itemFunc, elseFunc) {
   };
 
   var later = function (f) {
-    atFlushTime(function () {
+    Meteor._atFlush(function () {
       if (! stopped)
         withEventGuard(f);
     });
@@ -1124,6 +1105,12 @@ Spark.createLandmark = function (options, htmlFunc) {
   var html = htmlFunc(landmark);
   return renderer.annotate(
     html, Spark._ANNOTATION_LANDMARK, function (range) {
+      if (! range) {
+        // annotation not used
+        options.destroyed && options.destroyed.call(landmark);
+        return;
+      }
+
       _.extend(range, {
         preserve: preserve,
         constant: !! options.constant,
@@ -1140,9 +1127,6 @@ Spark.createLandmark = function (options, htmlFunc) {
 
       landmark._range = range;
       renderer.landmarkRanges.push(range);
-    }, function () {
-      // "annotation not used" callback
-      options.destroyed && options.destroyed.call(landmark);
     });
 };
 
diff --git a/packages/stream/stream_client.js b/packages/stream/stream_client.js
index 0f70866b75..6b03f33c76 100644
--- a/packages/stream/stream_client.js
+++ b/packages/stream/stream_client.js
@@ -47,11 +47,10 @@ Meteor._Stream = function (url) {
     retry_count: 0
   };
 
-  self.status_listeners = {}; // context.id -> context
+  self.status_listeners = (Meteor.deps && new Meteor.deps._ContextSet);
   self.status_changed = function () {
-    _.each(self.status_listeners, function (context) {
-      context.invalidate();
-    });
+    if (self.status_listeners)
+      self.status_listeners.invalidateAll();
   };
 
   //// Retry logic
@@ -120,13 +119,8 @@ _.extend(Meteor._Stream.prototype, {
   // Get current status. Reactive.
   status: function () {
     var self = this;
-    var context = Meteor.deps && Meteor.deps.Context.current;
-    if (context && !(context.id in self.status_listeners)) {
-      self.status_listeners[context.id] = context;
-      context.onInvalidate(function () {
-        delete self.status_listeners[context.id];
-      });
-    }
+    if (self.status_listeners)
+      self.status_listeners.addCurrentContext();
     return self.current_status;
   },
 
diff --git a/packages/test-helpers/onscreendiv.js b/packages/test-helpers/onscreendiv.js
index 47446c6f71..b594627e2b 100644
--- a/packages/test-helpers/onscreendiv.js
+++ b/packages/test-helpers/onscreendiv.js
@@ -50,11 +50,9 @@ OnscreenDiv.prototype.kill = function() {
   if (self.div.parentNode)
     self.div.parentNode.removeChild(self.div);
 
-  var cx = new Meteor.deps.Context;
-  cx.onInvalidate(function() {
+  Meteor._atFlush(function () {
     Spark.finalize(self.div);
   });
-  cx.invalidate();
 };
 
 // remove the DIV from the document
diff --git a/packages/test-helpers/reactivevar.js b/packages/test-helpers/reactivevar.js
index 2c3c4e7dde..0c789663ef 100644
--- a/packages/test-helpers/reactivevar.js
+++ b/packages/test-helpers/reactivevar.js
@@ -19,19 +19,11 @@ var ReactiveVar = function(initialValue) {
 
   this._value = (typeof initialValue === "undefined" ? null :
                  initialValue);
-  this._deps = {};
+  this._deps = new Meteor.deps._ContextSet;
 };
 
 ReactiveVar.prototype.get = function() {
-  var context = Meteor.deps.Context.current;
-  if (context && !(context.id in this._deps)) {
-    this._deps[context.id] = context;
-    var self = this;
-    context.onInvalidate(function() {
-      delete self._deps[context.id];
-    });
-  }
-
+  this._deps.addCurrentContext();
   return this._value;
 };
 
@@ -43,11 +35,9 @@ ReactiveVar.prototype.set = function(newValue) {
 
   this._value = newValue;
 
-  for(var id in this._deps)
-    this._deps[id].invalidate();
-
+  this._deps.invalidateAll();
 };
 
 ReactiveVar.prototype.numListeners = function() {
-  return _.keys(this._deps).length;
+  return _.keys(this._deps._contextsById).length;
 };
diff --git a/packages/test-helpers/wrappedfrag.js b/packages/test-helpers/wrappedfrag.js
index ad5f56e896..f019bf2fea 100644
--- a/packages/test-helpers/wrappedfrag.js
+++ b/packages/test-helpers/wrappedfrag.js
@@ -31,13 +31,11 @@ WrappedFrag.prototype.release = function() {
   // decrement frag's GC protection reference count
   // Clean up on flush, if hits 0.  Wait to decrement
   // so no one else cleans it up first.
-  var cx = new Meteor.deps.Context;
-  cx.onInvalidate(function() {
+  Meteor._atFlush(function () {
     if (! --frag["_protect"]) {
       Spark.finalize(frag);
     }
   });
-  cx.invalidate();
   return this;
 };
 
diff --git a/packages/test-in-browser/driver.js b/packages/test-in-browser/driver.js
index eb37196ca9..0a50601299 100644
--- a/packages/test-in-browser/driver.js
+++ b/packages/test-in-browser/driver.js
@@ -12,19 +12,12 @@ Meteor.startup(function () {
 });
 
 Template.test_table.running = function() {
-  var cx = Meteor.deps.Context.current;
-  if (cx) {
-    resultDeps.push(cx);
-  }
-
+  resultDeps.addCurrentContext();
   return running;
 };
 
 Template.test_table.passed = function() {
-  var cx = Meteor.deps.Context.current;
-  if (cx) {
-    resultDeps.push(cx);
-  }
+  resultDeps.addCurrentContext();
 
   // walk whole tree to look for failed tests
   var walk = function (groups) {
@@ -53,10 +46,7 @@ Template.test_table.passed = function() {
 
 
 Template.test_table.total_test_time = function() {
-  var cx = Meteor.deps.Context.current;
-  if (cx) {
-    resultDeps.push(cx);
-  }
+  resultDeps.addCurrentContext();
 
   // walk whole tree to get all tests
   var walk = function (groups) {
@@ -79,11 +69,7 @@ Template.test_table.total_test_time = function() {
 
 
 Template.test_table.data = function() {
-  var cx = Meteor.deps.Context.current;
-  if (cx) {
-    resultDeps.push(cx);
-  }
-
+  resultDeps.addCurrentContext();
   return resultTree;
 };
 
@@ -185,13 +171,10 @@ Template.event.is_debuggable = function() {
 
 
 var resultTree = [];
-var resultDeps = [];
+var resultDeps = new Meteor.deps._ContextSet;
 
 var _resultsChanged = function() {
-  _.each(resultDeps, function(cx) {
-    cx.invalidate();
-  });
-  resultDeps.length = 0;
+  resultDeps.invalidateAll();
 };
 
 var _testTime = function(t) {