add load-browser-scripts utility (#1077)

test/panic/util/load-browser-scripts.js

@@ -0,0 +1,41 @@
+module.exports = {
+  /**
+   * Loads scripts in PANIC clients
+   * @param browsers a Panic.ClientList of browsers
+   * @param paths an array of paths to desired .js files
+   * @returns Promise which will resolve when all browsers have loaded all dependencies
+   */
+  loadBrowserScripts: function (browsers, paths) {
+    var promises = [];
+    browsers.each(function (client, id) {
+      promises.push(client.run(function (test) {
+        test.async();
+        var env = test.props;
+        var imports = env.paths || [];
+        /** Loads a single script in the browser */
+        function load(src, cb) {
+          var script = document.createElement('script');
+          script.onload = cb; script.src = src;
+          document.head.appendChild(script);
+        }
+        /** Loads scripts in order, waiting on each to load before proceeding */
+        function loadAll(src, cb) {
+          if (src.length === 0) {
+            cb();
+            return;
+          }
+          var cur = src.shift();
+          // console.log('loading library:', cur);
+          load(cur, function () {
+            loadAll(src, cb);
+          });
+        }
+
+        loadAll(imports, function () {
+          test.done();
+        });
+      }, {paths: paths}));
+    });
+    return Promise.all(promises);
+  }
+};