refactor app directory structure and add tests

tests/node_modules/nightwatch/lib/api/assertions/hidden.js

@@ -0,0 +1,45 @@
+/**
+ * Checks if the given element is not visible on the page.
+ *
+ * ```
+ *    this.demoTest = function (client) {
+ *      browser.assert.hidden(".should_not_be_visible");
+ *    };
+ * ```
+ *
+ * @method hidden
+ * @param {string} selector The selector (CSS / Xpath) used to locate the element.
+ * @param {string} [message] Optional log message to display in the output. If missing, one is displayed by default.
+ * @api assertions
+ */
+
+var util = require('util');
+exports.assertion = function(selector, msg) {
+
+  var MSG_ELEMENT_NOT_FOUND = 'Testing if element <%s> is hidden. ' +
+    'Element could not be located.';
+
+  this.message = msg || util.format('Testing if element <%s> is hidden.', selector);
+  this.expected = true;
+
+  this.pass = function(value) {
+    return value === this.expected;
+  };
+
+  this.failure = function(result) {
+    var failed = result === false || result && result.status === -1;
+    if (failed) {
+      this.message = msg || util.format(MSG_ELEMENT_NOT_FOUND, selector);
+    }
+    return failed;
+  };
+
+  this.value = function(result) {
+    return !result.value;
+  };
+
+  this.command = function(callback) {
+    return this.api.isVisible(selector, callback);
+  };
+
+};