better error handling for jasmine task

grunt/tasks/webdriver-jasmine.js

@@ -7,10 +7,12 @@ module.exports = function(){
 
   var desiredCapabilities = {};
   if (config.desiredCapabilities) Object.keys(config.desiredCapabilities).forEach(function(key){
+    if (config.desiredCapabilities[key] === undefined) return;
     desiredCapabilities[key] = config.desiredCapabilities[key];
   });
+  grunt.verbose.writeln("desiredCapabilities", JSON.stringify(desiredCapabilities));
 
-  grunt.verbose.write('webdriver remote', JSON.stringify(config.webdriver.remote));
+  grunt.verbose.writeln('webdriver remote', JSON.stringify(config.webdriver.remote));
   var browser = wd.promiseChainRemote(config.webdriver.remote);
 
   browser.on('status', function(info) {
@@ -21,28 +23,48 @@ module.exports = function(){
     grunt.verbose.writeln(' > ' + meth, path, data || '');
   });
 
+  var report = null;
+
+  // browser._debugPromise();
   browser
     .init(desiredCapabilities)
+    .then(config.onStart && config.onStart.bind(config, browser))
     .get(config.url)
     .then(function(){return browser;})
     .then(getJSReport)
-    .then(config.onComplete && config.onComplete.bind(browser), config.onError && config.onError.bind(browser))
-    .fail(grunt.verbose.writeln.bind(grunt.verbose))
-    .fin(function(){
+    .then(function(data){ report = data; })
+    .fail(function(error){
+      grunt.log.error(error);
+      return browser
+        .eval('document.documentElement.innerText || document.documentElement.textContent')
+        .then(grunt.verbose.writeln.bind(grunt.verbose))
+        .then(function(){throw error})
+      ;
+    })
+    .finally(function(){
       if (grunt.option('webdriver-keep-open')) return;
       grunt.verbose.writeln('Closing the browser window. To keep it open, pass the --webdriver-keep-open flag to grunt.');
       return browser.quit();
     })
     .done(
-      taskSucceeded.bind(null,true),
-      taskSucceeded.bind(null,false)
+      function(){
+        if (config.onComplete) config.onComplete(report);
+        taskSucceeded(true);
+      },
+      function(error){
+        if (config.onError) config.onError(error);
+        taskSucceeded(false);
+      }
     )
   ;
 }
 
 function getJSReport(browser){
   return browser
     .waitForCondition("typeof window.jasmine != 'undefined'", 500)
+    .fail(function(error){
+      throw Error("The test page didn't load properly. " + error);
+    })
     .waitForCondition("typeof window.jasmine.getJSReport != 'undefined'", 10e3)
     .waitForCondition("window.testImageURL.running <= 0", 5e3)
     .eval("jasmine.getJSReport()")