Allow tests to be ignored by feature

test/spec/.eslintrc

@@ -6,6 +6,7 @@
     "afterLoadText": false,
     "expect": false,
     "proj4": false,
-    "sinon": false
+    "sinon": false,
+    "where": false
   }
 }

test/spec/ol/source/rastersource.test.js

@@ -9,7 +9,7 @@ var green = 'data:image/gif;base64,R0lGODlhAQABAPAAAAD/AP///yH5BAAAAAAALAAAA' +
 var blue = 'data:image/gif;base64,R0lGODlhAQABAPAAAAAA/////yH5BAAAAAAALAAAAA' +
     'ABAAEAAAICRAEAOw==';
 
-describe('ol.source.Raster', function() {
+where('Uint8ClampedArray').describe('ol.source.Raster', function() {
 
   var target, map, redSource, greenSource, blueSource, raster;
 

test/test-extensions.js

@@ -458,4 +458,25 @@
     }
   };
 
+  var features = {
+    Uint8ClampedArray: ('Uint8ClampedArray' in global)
+  };
+
+  /**
+   * Allow tests to be skipped where certain features are not available.  The
+   * provided key must be in the above `features` lookup.  Keys should
+   * correspond to the feature that is required, but can be any string.
+   * @param {string} key The required feature name.
+   * @return {Object} An object with a `describe` function that will run tests
+   *     if the required feature is available and skip them otherwise.
+   */
+  global.where = function(key) {
+    if (!(key in features)) {
+      throw new Error('where() called with unknown key: ' + key);
+    }
+    return {
+      describe: features[key] ? global.describe : global.xdescribe
+    };
+  };
+
 })(this);