diff --git a/src/tilesource.js b/src/tilesource.js
index 19ea1d63..74d7c315 100644
--- a/src/tilesource.js
+++ b/src/tilesource.js
@@ -347,7 +347,7 @@ $.TileSource.prototype = {
     getTileAtPoint: function(level, point) {
         var validPoint = point.x >= 0 && point.x <= 1 &&
             point.y >= 0 && point.y <= 1 / this.aspectRatio;
-        $.console.assert(validPoint, "[TileSource.getTileAtPoint] called with invalid point " + point.toString());
+        $.console.assert(validPoint, "[TileSource.getTileAtPoint] must be called with a valid point.");
 
         var widthScaled = this.dimensions.x * this.getLevelScale(level);
         var pixelX = point.x * widthScaled;
diff --git a/test/coverage.html b/test/coverage.html
index b04d5fda..65711abc 100644
--- a/test/coverage.html
+++ b/test/coverage.html
@@ -32,6 +32,7 @@
     <script src="/src/iiiftilesource.js"></script>
     <script src="/src/osmtilesource.js"></script>
     <script src="/src/tmstilesource.js"></script>
+    <script src="/src/zoomifytilesource.js"></script>
     <script src="/src/legacytilesource.js"></script>
     <script src="/src/imagetilesource.js"></script>
     <script src="/src/tilesourcecollection.js"></script>
diff --git a/test/modules/basic.js b/test/modules/basic.js
index c6164560..4d787ab4 100644
--- a/test/modules/basic.js
+++ b/test/modules/basic.js
@@ -331,7 +331,7 @@
                     height: 155
                 } ]
         } );
-        viewer.addHandler('tile-drawn', function() {
+        viewer.addOnceHandler('tile-drawn', function() {
             ok(OpenSeadragon.isCanvasTainted(viewer.drawer.context.canvas),
                 "Canvas should be tainted.");
             start();
@@ -355,7 +355,7 @@
                             height: 155
                         } ]
                 } );
-                viewer.addHandler('tile-drawn', function() {
+                viewer.addOnceHandler('tile-drawn', function() {
                     ok(!OpenSeadragon.isCanvasTainted(viewer.drawer.context.canvas),
                         "Canvas should not be tainted.");
                     start();
@@ -385,7 +385,7 @@
                     },
                     crossOriginPolicy : false
                 } );
-                viewer.addHandler('tile-drawn', function() {
+                viewer.addOnceHandler('tile-drawn', function() {
                     ok(OpenSeadragon.isCanvasTainted(viewer.drawer.context.canvas),
                         "Canvas should be tainted.");
                     start();
@@ -414,7 +414,7 @@
                         crossOriginPolicy : "Anonymous"
                     }
                 } );
-                viewer.addHandler('tile-drawn', function() {
+                viewer.addOnceHandler('tile-drawn', function() {
                     ok(!OpenSeadragon.isCanvasTainted(viewer.drawer.context.canvas),
                         "Canvas should not be tainted.");
                     start();