diff --git a/src/util/index.js b/src/util/index.js
index ca95383203..f7206750fc 100644
--- a/src/util/index.js
+++ b/src/util/index.js
@@ -5,6 +5,7 @@ var $ = require('jquery');
  */
 var util = require('./init');
 $.extend(util, require('./throttle'));
+$.extend(util, require('./mockVGL'));
 util.DistanceGrid = require('./distanceGrid.js');
 util.ClusterGroup = require('./clustering.js');
 
diff --git a/src/util/mockVGL.js b/src/util/mockVGL.js
new file mode 100644
index 0000000000..354ef8029e
--- /dev/null
+++ b/src/util/mockVGL.js
@@ -0,0 +1,189 @@
+/* eslint-disable camelcase */
+/* eslint-disable underscore/prefer-constant */
+
+var $ = require('jquery');
+var vgl = require('vgl');
+var vglRenderer = require('../gl/vglRenderer');
+
+var _renderWindow, _supported;
+
+module.exports = {};
+
+/**
+ * Replace vgl.renderer with a mocked version for testing in a non-webGL state.
+ * Use restoreVGLRenderer to unmock.  Call vgl.mockCounts() to get the number
+ * of times different webGL functions have been called.
+ *
+ * @param {boolean} [supported=true] If false, then the vgl renderer will
+ *      indicate that this is an unsupported browser environment.
+ */
+module.exports.mockVGLRenderer = function mockVGLRenderer(supported) {
+  'use strict';
+  var vgl = require('vgl');
+
+  if (supported === undefined) {
+    supported = true;
+  }
+
+  if (vgl._mocked) {
+    throw new Error('VGL renderer already mocked');
+  }
+
+  var mockCounts = {};
+  var count = function (name) {
+    mockCounts[name] = (mockCounts[name] || 0) + 1;
+  };
+  var noop = function (name) {
+    return function () {
+      count(name);
+    };
+  };
+  var _id = 0,
+      incID = function (name) {
+        return function () {
+          count(name);
+          _id += 1;
+          return _id;
+        };
+      };
+  /* The context largely does nothing. */
+  var default_context = {
+    activeTexture: noop('activeTexture'),
+    attachShader: noop('attachShader'),
+    bindAttribLocation: noop('bindAttribLocation'),
+    bindBuffer: noop('bindBuffer'),
+    bindFramebuffer: noop('bindFramebuffer'),
+    bindTexture: noop('bindTexture'),
+    blendFuncSeparate: noop('blendFuncSeparate'),
+    bufferData: noop('bufferData'),
+    bufferSubData: noop('bufferSubData'),
+    checkFramebufferStatus: function (key) {
+      count('checkFramebufferStatus');
+      if (key === vgl.GL.FRAMEBUFFER) {
+        return vgl.GL.FRAMEBUFFER_COMPLETE;
+      }
+    },
+    clear: noop('clear'),
+    clearColor: noop('clearColor'),
+    clearDepth: noop('clearDepth'),
+    compileShader: noop('compileShader'),
+    createBuffer: incID('createBuffer'),
+    createFramebuffer: noop('createFramebuffer'),
+    createProgram: incID('createProgram'),
+    createShader: incID('createShader'),
+    createTexture: incID('createTexture'),
+    deleteBuffer: noop('deleteBuffer'),
+    deleteProgram: noop('deleteProgram'),
+    deleteShader: noop('deleteShader'),
+    deleteTexture: noop('deleteTexture'),
+    depthFunc: noop('depthFunc'),
+    disable: noop('disable'),
+    disableVertexAttribArray: noop('disableVertexAttribArray'),
+    drawArrays: noop('drawArrays'),
+    enable: noop('enable'),
+    enableVertexAttribArray: noop('enableVertexAttribArray'),
+    finish: noop('finish'),
+    getExtension: incID('getExtension'),
+    getParameter: function (key) {
+      count('getParameter');
+      if (key === vgl.GL.DEPTH_BITS) {
+        return 16;
+      }
+    },
+    getProgramParameter: function (id, key) {
+      count('getProgramParameter');
+      if (key === vgl.GL.LINK_STATUS) {
+        return true;
+      }
+    },
+    getShaderInfoLog: function () {
+      count('getShaderInfoLog');
+      return 'log';
+    },
+    getShaderParameter: function (id, key) {
+      count('getShaderParameter');
+      if (key === vgl.GL.COMPILE_STATUS) {
+        return true;
+      }
+    },
+    getUniformLocation: incID('getUniformLocation'),
+    isEnabled: function (key) {
+      count('isEnabled');
+      if (key === vgl.GL.BLEND) {
+        return true;
+      }
+    },
+    linkProgram: noop('linkProgram'),
+    pixelStorei: noop('pixelStorei'),
+    shaderSource: noop('shaderSource'),
+    texImage2D: noop('texImage2D'),
+    texParameteri: noop('texParameteri'),
+    uniform1iv: noop('uniform1iv'),
+    uniform1fv: noop('uniform1fv'),
+    uniform2fv: noop('uniform2fv'),
+    uniform3fv: noop('uniform3fv'),
+    uniform4fv: noop('uniform4fv'),
+    uniformMatrix3fv: noop('uniformMatrix3fv'),
+    uniformMatrix4fv: noop('uniformMatrix4fv'),
+    useProgram: noop('useProgram'),
+    vertexAttribPointer: noop('vertexAttribPointer'),
+    vertexAttrib3fv: noop('vertexAttrib3fv'),
+    viewport: noop('viewport')
+  };
+
+  _renderWindow = vgl.renderWindow;
+  var mockedRenderWindow = function () {
+    /* Temporarily put back the original definition of renderWindow so that the
+     * class instance will be instantiated correctly. */
+    vgl.renderWindow = _renderWindow;
+    var m_this = new vgl.renderWindow(),
+        m_context;
+    vgl.renderWindow = mockedRenderWindow;
+
+    m_this._setup = function () {
+      var i, renderers = m_this.renderers(),
+          wsize = m_this.windowSize(),
+          wpos = m_this.windowPosition();
+
+      m_context = $.extend({}, default_context);
+
+      for (i = 0; i < renderers.length; i += 1) {
+        if ((renderers[i].width() > wsize[0]) ||
+            renderers[i].width() === 0 ||
+            (renderers[i].height() > wsize[1]) ||
+            renderers[i].height() === 0) {
+          renderers[i].resize(wpos[0], wpos[1], wsize[0], wsize[1]);
+        }
+      }
+      return true;
+    };
+    m_this.context = function () {
+      return m_context;
+    };
+    return m_this;
+  };
+  vgl.renderWindow = mockedRenderWindow;
+
+  _supported = vglRenderer.supported;
+  vglRenderer.supported = function () {
+    return !!supported;
+  };
+
+  vgl._mocked = true;
+  vgl.mockCounts = function () {
+    return mockCounts;
+  };
+};
+
+/**
+ * Unmock the vgl renderer.
+ */
+module.exports.restoreVGLRenderer = function () {
+  if (vgl._mocked) {
+    vgl.renderWindow = _renderWindow;
+    vglRenderer.supported = _supported;
+    delete vgl._mocked;
+    // delete vgl._mockedRenderWindow;
+    delete vgl.mockCounts;
+  }
+};
diff --git a/testing/test-data/base-images.tgz.md5 b/testing/test-data/base-images.tgz.md5
index f2458e316b..c462aac6a5 100644
--- a/testing/test-data/base-images.tgz.md5
+++ b/testing/test-data/base-images.tgz.md5
@@ -1 +1 @@
-f2fa25ac074a409ccc072c3444edfb6f
\ No newline at end of file
+c9987ae6444d8124142e040ae06b7468
\ No newline at end of file
diff --git a/testing/test-data/base-images.tgz.url b/testing/test-data/base-images.tgz.url
index 7bc3557343..4418bdb639 100644
--- a/testing/test-data/base-images.tgz.url
+++ b/testing/test-data/base-images.tgz.url
@@ -1 +1 @@
-https://data.kitware.com/api/v1/file/58c934128d777f0aef5d79a7/download
\ No newline at end of file
+https://data.kitware.com/api/v1/file/590103778d777f16d01e04fb/download
\ No newline at end of file
diff --git a/tests/cases/annotation.js b/tests/cases/annotation.js
index 6e6b9065f9..557178ad76 100644
--- a/tests/cases/annotation.js
+++ b/tests/cases/annotation.js
@@ -5,8 +5,8 @@ describe('geo.annotation', function () {
 
   var $ = require('jquery');
   var geo = require('../test-utils').geo;
-  var mockVGLRenderer = require('../test-utils').mockVGLRenderer;
-  var restoreVGLRenderer = require('../test-utils').restoreVGLRenderer;
+  var mockVGLRenderer = geo.util.mockVGLRenderer;
+  var restoreVGLRenderer = geo.util.restoreVGLRenderer;
 
   beforeEach(function () {
     mockVGLRenderer();
diff --git a/tests/cases/annotationLayer.js b/tests/cases/annotationLayer.js
index 6ba1cadc57..e1be239bd1 100644
--- a/tests/cases/annotationLayer.js
+++ b/tests/cases/annotationLayer.js
@@ -5,8 +5,8 @@ describe('geo.annotationLayer', function () {
 
   var $ = require('jquery');
   var geo = require('../test-utils').geo;
-  var mockVGLRenderer = require('../test-utils').mockVGLRenderer;
-  var restoreVGLRenderer = require('../test-utils').restoreVGLRenderer;
+  var mockVGLRenderer = geo.util.mockVGLRenderer;
+  var restoreVGLRenderer = geo.util.restoreVGLRenderer;
 
   beforeEach(function () {
     mockVGLRenderer();
diff --git a/tests/cases/choroplethFeature.js b/tests/cases/choroplethFeature.js
index 1c4de3376d..3130f004cf 100644
--- a/tests/cases/choroplethFeature.js
+++ b/tests/cases/choroplethFeature.js
@@ -1,9 +1,9 @@
 // Test geo.choroplethFeature and geo.gl.choroplethFeature
 
-var geo = require('../test-utils').geo;
 var $ = require('jquery');
-var mockVGLRenderer = require('../test-utils').mockVGLRenderer;
-var restoreVGLRenderer = require('../test-utils').restoreVGLRenderer;
+var geo = require('../test-utils').geo;
+var mockVGLRenderer = geo.util.mockVGLRenderer;
+var restoreVGLRenderer = geo.util.restoreVGLRenderer;
 
 describe('geo.choroplethFeature', function () {
   'use strict';
@@ -130,9 +130,9 @@ describe('geo.choroplethFeature', function () {
         .scalarValue(scalarData[0])).toBe(10);
       expect(choropleth.choropleth.get('accessors')()
         .geoId(mpdata[0])).toBe(0);
-      expect(Object.keys(choropleth.choropleth.get())).toEqual(
-        ['colorRange', 'scale', 'accessors', 'scalar',
-         'scalarAggregator', 'name']);
+      expect(Object.keys(choropleth.choropleth.get())).toEqual([
+        'colorRange', 'scale', 'accessors', 'scalar',
+        'scalarAggregator', 'name']);
       restoreVGLRenderer();
     });
   });
diff --git a/tests/cases/contourWrap.js b/tests/cases/contourWrap.js
index 0c80d310a8..92bc9d950b 100644
--- a/tests/cases/contourWrap.js
+++ b/tests/cases/contourWrap.js
@@ -1,12 +1,12 @@
-var geo = require('../test-utils').geo;
 var $ = require('jquery');
 
 describe('Contour Feature', function () {
   'use strict';
 
   var map, layer;
-  var mockVGLRenderer = require('../test-utils').mockVGLRenderer;
-  var restoreVGLRenderer = require('../test-utils').restoreVGLRenderer;
+  var geo = require('../test-utils').geo;
+  var mockVGLRenderer = geo.util.mockVGLRenderer;
+  var restoreVGLRenderer = geo.util.restoreVGLRenderer;
 
   beforeEach(function () {
     $('<div id="map-contour-wrap"/>')
diff --git a/tests/cases/lineFeature.js b/tests/cases/lineFeature.js
index 6c9eaaa30a..431a9189e4 100644
--- a/tests/cases/lineFeature.js
+++ b/tests/cases/lineFeature.js
@@ -1,14 +1,14 @@
 // Test geo.lineFeature, geo.d3.lineFeature, geo.canvas.lineFeature, and
 // geo.gl.lineFeature
 
-var geo = require('../test-utils').geo;
 var $ = require('jquery');
 var mockAnimationFrame = require('../test-utils').mockAnimationFrame;
 var stepAnimationFrame = require('../test-utils').stepAnimationFrame;
 var unmockAnimationFrame = require('../test-utils').unmockAnimationFrame;
+var geo = require('../test-utils').geo;
+var mockVGLRenderer = geo.util.mockVGLRenderer;
+var restoreVGLRenderer = geo.util.restoreVGLRenderer;
 var vgl = require('vgl');
-var mockVGLRenderer = require('../test-utils').mockVGLRenderer;
-var restoreVGLRenderer = require('../test-utils').restoreVGLRenderer;
 var waitForIt = require('../test-utils').waitForIt;
 var logCanvas2D = require('../test-utils').logCanvas2D;
 
diff --git a/tests/cases/osmLayer.js b/tests/cases/osmLayer.js
index be29953b2b..c15ab6bd2e 100644
--- a/tests/cases/osmLayer.js
+++ b/tests/cases/osmLayer.js
@@ -1,7 +1,5 @@
 // Test geo.core.osmLayer
-var geo = require('../test-utils').geo;
 var $ = require('jquery');
-var vgl = require('vgl');
 var mockAnimationFrame = require('../test-utils').mockAnimationFrame;
 var stepAnimationFrame = require('../test-utils').stepAnimationFrame;
 var unmockAnimationFrame = require('../test-utils').unmockAnimationFrame;
@@ -13,8 +11,10 @@ describe('geo.core.osmLayer', function () {
   var waitForIt = require('../test-utils').waitForIt;
   var submitNote = require('../test-utils').submitNote;
   // var logCanvas2D = require('../test-utils').logCanvas2D;
-  var mockVGLRenderer = require('../test-utils').mockVGLRenderer;
-  var restoreVGLRenderer = require('../test-utils').restoreVGLRenderer;
+  var geo = require('../test-utils').geo;
+  var mockVGLRenderer = geo.util.mockVGLRenderer;
+  var restoreVGLRenderer = geo.util.restoreVGLRenderer;
+  var vgl = require('vgl');
   var closeToEqual = require('../test-utils').closeToEqual;
 
   function create_map(opts) {
diff --git a/tests/cases/pointFeature.js b/tests/cases/pointFeature.js
index 52ea343559..16c3701124 100644
--- a/tests/cases/pointFeature.js
+++ b/tests/cases/pointFeature.js
@@ -1,13 +1,13 @@
 // Test geo.pointFeature, geo.d3.pointFeature, and geo.gl.pointFeature
 
-var geo = require('../test-utils').geo;
 var $ = require('jquery');
 var mockAnimationFrame = require('../test-utils').mockAnimationFrame;
 var stepAnimationFrame = require('../test-utils').stepAnimationFrame;
 var unmockAnimationFrame = require('../test-utils').unmockAnimationFrame;
+var geo = require('../test-utils').geo;
+var mockVGLRenderer = geo.util.mockVGLRenderer;
+var restoreVGLRenderer = geo.util.restoreVGLRenderer;
 var vgl = require('vgl');
-var mockVGLRenderer = require('../test-utils').mockVGLRenderer;
-var restoreVGLRenderer = require('../test-utils').restoreVGLRenderer;
 var waitForIt = require('../test-utils').waitForIt;
 
 describe('geo.pointFeature', function () {
diff --git a/tests/cases/polygonFeature.js b/tests/cases/polygonFeature.js
index e7eca2662b..d50867b687 100644
--- a/tests/cases/polygonFeature.js
+++ b/tests/cases/polygonFeature.js
@@ -1,10 +1,10 @@
 // Test geo.polygonFeature and geo.gl.polygonFeature
 
-var geo = require('../test-utils').geo;
 var $ = require('jquery');
+var geo = require('../test-utils').geo;
+var mockVGLRenderer = geo.util.mockVGLRenderer;
+var restoreVGLRenderer = geo.util.restoreVGLRenderer;
 var vgl = require('vgl');
-var mockVGLRenderer = require('../test-utils').mockVGLRenderer;
-var restoreVGLRenderer = require('../test-utils').restoreVGLRenderer;
 var waitForIt = require('../test-utils').waitForIt;
 // var closeToArray = require('../test-utils').closeToArray;
 
diff --git a/tests/cases/quadFeature.js b/tests/cases/quadFeature.js
index 2ba3d1a27f..d5d1e5d038 100644
--- a/tests/cases/quadFeature.js
+++ b/tests/cases/quadFeature.js
@@ -2,11 +2,11 @@
 
 /* globals Image */
 
-var geo = require('../test-utils').geo;
 var $ = require('jquery');
+var geo = require('../test-utils').geo;
+var mockVGLRenderer = geo.util.mockVGLRenderer;
+var restoreVGLRenderer = geo.util.restoreVGLRenderer;
 var vgl = require('vgl');
-var mockVGLRenderer = require('../test-utils').mockVGLRenderer;
-var restoreVGLRenderer = require('../test-utils').restoreVGLRenderer;
 var waitForIt = require('../test-utils').waitForIt;
 var closeToArray = require('../test-utils').closeToArray;
 var logCanvas2D = require('../test-utils').logCanvas2D;
diff --git a/tests/cases/registry.js b/tests/cases/registry.js
index 0f14ab54da..98a171075f 100644
--- a/tests/cases/registry.js
+++ b/tests/cases/registry.js
@@ -2,8 +2,8 @@ describe('geo.registry', function () {
   'use strict';
 
   var geo = require('../test-utils').geo;
-  var mockVGLRenderer = require('../test-utils').mockVGLRenderer;
-  var restoreVGLRenderer = require('../test-utils').restoreVGLRenderer;
+  var mockVGLRenderer = geo.util.mockVGLRenderer;
+  var restoreVGLRenderer = geo.util.restoreVGLRenderer;
 
   describe('Check rendererForFeatures', function () {
     it('specific features', function () {
diff --git a/tests/cases/renderers.js b/tests/cases/renderers.js
index 4755ba0330..a754cf7623 100644
--- a/tests/cases/renderers.js
+++ b/tests/cases/renderers.js
@@ -6,8 +6,8 @@ describe('renderers', function () {
   var supported = true;
   var fallback = 'd3';
   var geo = require('../test-utils').geo;
-  var mockVGLRenderer = require('../test-utils').mockVGLRenderer;
-  var restoreVGLRenderer = require('../test-utils').restoreVGLRenderer;
+  var mockVGLRenderer = geo.util.mockVGLRenderer;
+  var restoreVGLRenderer = geo.util.restoreVGLRenderer;
 
   function create_simple_renderer() {
     var simpleRenderer = function (arg) {
diff --git a/tests/test-utils.js b/tests/test-utils.js
index dd42ba68a8..b33d4b87b3 100644
--- a/tests/test-utils.js
+++ b/tests/test-utils.js
@@ -1,14 +1,10 @@
 /* These are functions we want available to jasmine tests. */
-/* exported waitForIt, mockVGLRenderer, closeToArray, closeToEqual, logCanvas2D, submitNote */
+/* exported waitForIt, closeToArray, closeToEqual, logCanvas2D, submitNote */
 /* global CanvasRenderingContext2D */
 
-var vgl = require('vgl');
-var _renderWindow = vgl.renderWindow;
-
 var $ = require('jquery');
 
 var geo = require('../src');
-var _supported = geo.gl.vglRenderer.supported;
 var bowser = require('bowser');
 
 module.exports = {};
@@ -96,159 +92,6 @@ module.exports.closeToEqual = function closeToEqual(o1, o2, precision) {
   return true;
 };
 
-/**
- * Replace vgl.renderer with a mocked version for phantom tests.
- * Returns a function that, when called, will restore vgl to its
- * default state.
- *
- * @param {boolean} [supported=true] If false, then the vgl renderer
- * will indicate that this is an unsupported browser environment.
- */
-module.exports.mockVGLRenderer = function mockVGLRenderer(supported) {
-  'use strict';
-  var vgl = require('vgl');
-
-  if (supported === undefined) {
-    supported = true;
-  }
-
-  if (vgl._mocked) {
-    throw new Error('VGL renderer already mocked');
-  }
-
-  var mockCounts = {};
-  var count = function (name) {
-    mockCounts[name] = (mockCounts[name] || 0) + 1;
-  };
-  var noop = function (name) {
-    return function () {
-      count(name);
-    };
-  };
-  var _id = 0,
-      incID = function (name) {
-        return function () {
-          count(name);
-          _id += 1;
-          return _id;
-        };
-      };
-  /* The context largely does nothing. */
-  var m_context = {
-    activeTexture: noop('activeTexture'),
-    attachShader: noop('attachShader'),
-    bindAttribLocation: noop('bindAttribLocation'),
-    bindBuffer: noop('bindBuffer'),
-    bindFramebuffer: noop('bindFramebuffer'),
-    bindTexture: noop('bindTexture'),
-    blendFuncSeparate: noop('blendFuncSeparate'),
-    bufferData: noop('bufferData'),
-    bufferSubData: noop('bufferSubData'),
-    checkFramebufferStatus: function (key) {
-      count('checkFramebufferStatus');
-      if (key === vgl.GL.FRAMEBUFFER) {
-        return vgl.GL.FRAMEBUFFER_COMPLETE;
-      }
-    },
-    clear: noop('clear'),
-    clearColor: noop('clearColor'),
-    clearDepth: noop('clearDepth'),
-    compileShader: noop('compileShader'),
-    createBuffer: incID('createBuffer'),
-    createFramebuffer: noop('createFramebuffer'),
-    createProgram: incID('createProgram'),
-    createShader: incID('createShader'),
-    createTexture: incID('createTexture'),
-    deleteBuffer: noop('deleteBuffer'),
-    deleteProgram: noop('deleteProgram'),
-    deleteShader: noop('deleteShader'),
-    deleteTexture: noop('deleteTexture'),
-    depthFunc: noop('depthFunc'),
-    disable: noop('disable'),
-    disableVertexAttribArray: noop('disableVertexAttribArray'),
-    drawArrays: noop('drawArrays'),
-    enable: noop('enable'),
-    enableVertexAttribArray: noop('enableVertexAttribArray'),
-    finish: noop('finish'),
-    getExtension: incID('getExtension'),
-    getParameter: function (key) {
-      count('getParameter');
-      if (key === vgl.GL.DEPTH_BITS) {
-        return 16;
-      }
-    },
-    getProgramParameter: function (id, key) {
-      count('getProgramParameter');
-      if (key === vgl.GL.LINK_STATUS) {
-        return true;
-      }
-    },
-    getShaderInfoLog: function () {
-      count('getShaderInfoLog');
-      return 'log';
-    },
-    getShaderParameter: function (id, key) {
-      count('getShaderParameter');
-      if (key === vgl.GL.COMPILE_STATUS) {
-        return true;
-      }
-    },
-    getUniformLocation: incID('getUniformLocation'),
-    isEnabled: function (key) {
-      count('isEnabled');
-      if (key === vgl.GL.BLEND) {
-        return true;
-      }
-    },
-    linkProgram: noop('linkProgram'),
-    pixelStorei: noop('pixelStorei'),
-    shaderSource: noop('shaderSource'),
-    texImage2D: noop('texImage2D'),
-    texParameteri: noop('texParameteri'),
-    uniform1iv: noop('uniform1iv'),
-    uniform1fv: noop('uniform1fv'),
-    uniform2fv: noop('uniform2fv'),
-    uniform3fv: noop('uniform3fv'),
-    uniform4fv: noop('uniform4fv'),
-    uniformMatrix3fv: noop('uniformMatrix3fv'),
-    uniformMatrix4fv: noop('uniformMatrix4fv'),
-    useProgram: noop('useProgram'),
-    vertexAttribPointer: noop('vertexAttribPointer'),
-    vertexAttrib3fv: noop('vertexAttrib3fv'),
-    viewport: noop('viewport')
-  };
-
-  /* Our mock has only a single renderWindow */
-  var m_renderWindow = vgl.renderWindow();
-  m_renderWindow._setup = function () {
-    return true;
-  };
-  m_renderWindow.context = function () {
-    return m_context;
-  };
-  vgl.renderWindow = function () {
-    return m_renderWindow;
-  };
-  geo.gl.vglRenderer.supported = function () {
-    return !!supported;
-  };
-
-  vgl._mocked = true;
-  vgl.mockCounts = function () {
-    return mockCounts;
-  };
-};
-
-/**
- * Restore the vgl renderer to a pristine state.
- */
-module.exports.restoreVGLRenderer = function () {
-  vgl.renderWindow = _renderWindow;
-  geo.gl.vglRenderer.supported = _supported;
-  delete vgl._mocked;
-  delete vgl.mockCounts;
-};
-
 /**
  * Add counters for various canvas calls so we can tell if they have been used.
  */