diff --git a/test/spec/ol/collection.test.js b/test/spec/ol/collection.test.js
index a861a07ba4..77d746aef2 100644
--- a/test/spec/ol/collection.test.js
+++ b/test/spec/ol/collection.test.js
@@ -80,7 +80,7 @@ describe('ol.collection', function() {
     describe('on an empty collection', function() {
       it('does not call the callback', function() {
         collection.forEach(cb);
-        expect(cb.called).to.not.be.ok();
+        expect(cb).to.not.be.called();
       });
     });
     describe('on a non-empty collection', function() {
@@ -116,7 +116,7 @@ describe('ol.collection', function() {
       var cb = sinon.spy();
       goog.events.listen(collection, ol.CollectionEventType.REMOVE, cb);
       expect(collection.remove(1)).to.eql(1);
-      expect(cb.called).to.be.ok();
+      expect(cb).to.be.called();
       expect(cb.lastCall.args[0].elem).to.eql(1);
     });
     it('does not remove more than one matching element', function() {
@@ -206,21 +206,21 @@ describe('ol.collection', function() {
     describe('insertAt', function() {
       it('triggers length_changed event', function() {
         collection.insertAt(2, 3);
-        expect(cb.called).to.be.ok();
+        expect(cb).to.be.called();
       });
     });
 
     describe('removeAt', function() {
       it('triggers length_changed event', function() {
         collection.removeAt(0);
-        expect(cb.called).to.be.ok();
+        expect(cb).to.be.called();
       });
     });
 
     describe('setAt', function() {
       it('does not trigger length_changed event', function() {
         collection.setAt(1, 1);
-        expect(cb.called).to.not.be.ok();
+        expect(cb).to.not.be.called();
       });
     });
   });
diff --git a/test/spec/ol/layer/vectorlayer.test.js b/test/spec/ol/layer/vectorlayer.test.js
index 4e2ac781ea..34e73c1e06 100644
--- a/test/spec/ol/layer/vectorlayer.test.js
+++ b/test/spec/ol/layer/vectorlayer.test.js
@@ -56,7 +56,7 @@ describe('ol.layer.Vector', function() {
     it('can filter by geometry type using its GeometryType index', function() {
       sinon.spy(geomFilter, 'applies');
       var lineStrings = layer.getFeatures(geomFilter);
-      expect(geomFilter.applies.called).to.not.be.ok();
+      expect(geomFilter.applies).to.not.be.called();
       expect(lineStrings.length).to.eql(4);
       expect(lineStrings).to.contain(features[4]);
     });
@@ -64,7 +64,7 @@ describe('ol.layer.Vector', function() {
     it('can filter by extent using its RTree', function() {
       sinon.spy(extentFilter, 'applies');
       var subset = layer.getFeatures(extentFilter);
-      expect(extentFilter.applies.called).to.not.be.ok();
+      expect(extentFilter.applies).to.not.be.called();
       expect(subset.length).to.eql(4);
       expect(subset).not.to.contain(features[7]);
     });
@@ -78,8 +78,8 @@ describe('ol.layer.Vector', function() {
       sinon.spy(filter2, 'applies');
       var subset1 = layer.getFeatures(filter1);
       var subset2 = layer.getFeatures(filter2);
-      expect(filter1.applies.called).to.not.be.ok();
-      expect(filter2.applies.called).to.not.be.ok();
+      expect(filter1.applies).to.not.be.called();
+      expect(filter2.applies).to.not.be.called();
       expect(subset1.length).to.eql(0);
       expect(subset2.length).to.eql(0);
     });
@@ -89,7 +89,7 @@ describe('ol.layer.Vector', function() {
           ol.filter.LogicalOperator.OR);
       sinon.spy(filter, 'applies');
       var subset = layer.getFeatures(filter);
-      expect(filter.applies.called).to.be.ok();
+      expect(filter.applies).to.be.called();
       expect(subset.length).to.eql(8);
     });
 
diff --git a/test/spec/ol/map.test.js b/test/spec/ol/map.test.js
index a6d6658e7a..9e9175e28c 100644
--- a/test/spec/ol/map.test.js
+++ b/test/spec/ol/map.test.js
@@ -198,7 +198,7 @@ describe('ol.Map', function() {
       // confirm that the center is somewhere between origin and destination
       // after a short delay
       setTimeout(function() {
-        expect(o.callback.called).to.be.ok();
+        expect(o.callback).to.be.called();
         var loc = map.getView().getCenter();
         expect(loc.x).not.to.eql(origin.x);
         expect(loc.y).not.to.eql(origin.y);
diff --git a/test/spec/ol/object.test.js b/test/spec/ol/object.test.js
index 9e0e4e1f89..2facaaed56 100644
--- a/test/spec/ol/object.test.js
+++ b/test/spec/ol/object.test.js
@@ -116,17 +116,17 @@ describe('ol.Object', function() {
 
     it('dispatches events', function() {
       o.notify('k');
-      expect(listener1.called).to.be.ok();
+      expect(listener1).to.be.called();
     });
 
     it('dispatches generic change events to bound objects', function() {
       o.notify('k');
-      expect(listener2.called).to.be.ok();
+      expect(listener2).to.be.called();
     });
 
     it('dispatches events to bound objects', function() {
       o.notify('k');
-      expect(listener3.called).to.be.ok();
+      expect(listener3).to.be.called();
     });
   });
 
@@ -149,7 +149,7 @@ describe('ol.Object', function() {
 
     it('dispatches events to object', function() {
       o.set('k', 1);
-      expect(listener1.called).to.be.ok();
+      expect(listener1).to.be.called();
 
       expect(o.getKeys()).to.eql(['k']);
       expect(o2.getKeys()).to.eql(['k']);
@@ -157,17 +157,17 @@ describe('ol.Object', function() {
 
     it('dispatches generic change events to object', function() {
       o.set('k', 1);
-      expect(listener2.called).to.be.ok();
+      expect(listener2).to.be.called();
     });
 
     it('dispatches events to bound object', function() {
       o.set('k', 1);
-      expect(listener3.called).to.be.ok();
+      expect(listener3).to.be.called();
     });
 
     it('dispatches events to object bound to', function() {
       o2.set('k', 2);
-      expect(listener1.called).to.be.ok();
+      expect(listener1).to.be.called();
 
       expect(o.getKeys()).to.eql(['k']);
       expect(o2.getKeys()).to.eql(['k']);
@@ -175,7 +175,7 @@ describe('ol.Object', function() {
 
     it('dispatches generic change events to object bound to', function() {
       o2.set('k', 2);
-      expect(listener2.called).to.be.ok();
+      expect(listener2).to.be.called();
     });
   });
 
@@ -300,8 +300,8 @@ describe('ol.Object', function() {
       expect(o.get('k2')).to.be(undefined);
       expect(o2.get('k2')).to.eql(1);
       expect(o2.get('k1')).to.be(undefined);
-      expect(listener1.called).to.be.ok();
-      expect(listener2.called).to.be.ok();
+      expect(listener1).to.be.called();
+      expect(listener2).to.be.called();
 
       expect(o.getKeys()).to.eql(['k1']);
       expect(o2.getKeys()).to.eql(['k2']);
@@ -392,7 +392,7 @@ describe('ol.Object', function() {
       it('does not call the setter', function() {
         o.set('x', 1);
         expect(o.get('x')).to.eql(1);
-        expect(o.setX.called).to.not.be.ok();
+        expect(o.setX).to.not.be.called();
 
         expect(o.getKeys()).to.eql(['x']);
       });
@@ -403,7 +403,7 @@ describe('ol.Object', function() {
         var o2 = new ol.Object();
         o2.bindTo('x', o);
         o2.set('x', 1);
-        expect(o.setX.called).to.be.ok();
+        expect(o.setX).to.be.called();
         expect(o.get('x')).to.eql(1);
 
         expect(o.getKeys()).to.eql(['x']);
@@ -423,7 +423,7 @@ describe('ol.Object', function() {
     describe('without bind', function() {
       it('does not call the getter', function() {
         expect(o.get('x')).to.be(undefined);
-        expect(o.getX.called).to.not.be.ok();
+        expect(o.getX).to.not.be.called();
       });
     });
 
@@ -432,7 +432,7 @@ describe('ol.Object', function() {
         var o2 = new ol.Object();
         o2.bindTo('x', o);
         expect(o2.get('x')).to.eql(1);
-        expect(o.getX.called).to.be.ok();
+        expect(o.getX).to.be.called();
 
         expect(o.getKeys()).to.eql([]);
         expect(o2.getKeys()).to.eql(['x']);
@@ -467,8 +467,8 @@ describe('ol.Object', function() {
 
     it('dispatches the expected event', function() {
       o.set('K', 1);
-      expect(listener1.called).to.be.ok();
-      expect(listener2.called).to.not.be.ok();
+      expect(listener1).to.be.called();
+      expect(listener2).to.not.be.called();
 
       expect(o.getKeys()).to.eql(['K']);
     });
diff --git a/test/spec/ol/rectangle.test.js b/test/spec/ol/rectangle.test.js
index c81fcf3037..50bd9a4df5 100644
--- a/test/spec/ol/rectangle.test.js
+++ b/test/spec/ol/rectangle.test.js
@@ -17,9 +17,6 @@ describe('ol.Rectangle', function() {
 
     beforeEach(function() {
       rectangle1 = new ol.Rectangle(50, 50, 100, 100);
-      expect.Assertion.prototype.intersectWith = function(other) {
-        return this.obj.intersects(other);
-      };
     });
 
     it('returns the expected value', function() {
diff --git a/test/test-extensions.js b/test/test-extensions.js
index dbf5add6b6..abb0ab0ea7 100644
--- a/test/test-extensions.js
+++ b/test/test-extensions.js
@@ -24,6 +24,15 @@ expect.Assertion.prototype.roughlyEqual = function(other, tol) {
 };
 
 
+expect.Assertion.prototype.intersectWith = function(other) {
+  return this.obj.intersects(other);
+};
+
+
+expect.Assertion.prototype.called = function() {
+  return this.obj.called;
+};
+
 
 // helper functions for async testing
 (function(global) {