Set "root" property on Suite correctly (#3632)

* suite constructor

* tests

* suite.js corrections and new tests

lib/mocha.js

@@ -92,7 +92,7 @@ function Mocha(options) {
   this.files = [];
   this.options = options;
   // root suite
-  this.suite = new exports.Suite('', new exports.Context());
+  this.suite = new exports.Suite('', new exports.Context(), true);
 
   if ('useColors' in options) {
     utils.deprecate(

lib/suite.js

@@ -39,15 +39,18 @@ exports.create = function(parent, title) {
 };
 
 /**
- * Initialize a new `Suite` with the given `title` and `ctx`. Derived from [EventEmitter](https://nodejs.org/api/events.html#events_class_eventemitter)
+ * Constructs a new `Suite` instance with the given `title`, `ctx`, and `isRoot`.
  *
- * @memberof Mocha
  * @public
  * @class
- * @param {string} title
- * @param {Context} parentContext
+ * @extends EventEmitter
+ * @memberof Mocha
+ * @see {@link https://nodejs.org/api/events.html#events_class_eventemitter|EventEmitter}
+ * @param {string} title - Suite title.
+ * @param {Context} parentContext - Parent context instance.
+ * @param {boolean} [isRoot=false] - Whether this is the root suite.
  */
-function Suite(title, parentContext) {
+function Suite(title, parentContext, isRoot) {
   if (!utils.isString(title)) {
     throw createInvalidArgumentTypeError(
       'Suite argument "title" must be a string. Received type "' +
@@ -68,7 +71,7 @@ function Suite(title, parentContext) {
   this._beforeAll = [];
   this._afterEach = [];
   this._afterAll = [];
-  this.root = !title;
+  this.root = isRoot === true;
   this._timeout = 2000;
   this._enableTimeouts = true;
   this._slow = 75;
@@ -324,6 +327,7 @@ Suite.prototype.afterEach = function(title, fn) {
  */
 Suite.prototype.addSuite = function(suite) {
   suite.parent = this;
+  suite.root = false;
   suite.timeout(this.timeout());
   suite.retries(this.retries());
   suite.enableTimeouts(this.enableTimeouts());

test/unit/suite.spec.js

@@ -302,6 +302,27 @@ describe('Suite', function() {
     });
   });
 
+  describe('.create()', function() {
+    before(function() {
+      this.first = new Suite('Root suite', {}, true);
+      this.second = new Suite('RottenRoot suite', {}, true);
+      this.first.addSuite(this.second);
+    });
+
+    it('does not create a second root suite', function() {
+      expect(this.second.parent, 'to be', this.first);
+      expect(this.first.root, 'to be', true);
+      expect(this.second.root, 'to be', false);
+    });
+
+    it('does not denote the root suite by being titleless', function() {
+      var emptyTitleSuite = Suite.create(this.second, '');
+      expect(emptyTitleSuite.parent, 'to be', this.second);
+      expect(emptyTitleSuite.root, 'to be', false);
+      expect(this.second.root, 'to be', false);
+    });
+  });
+
   describe('.addSuite()', function() {
     beforeEach(function() {
       this.first = new Suite('First suite');
@@ -390,8 +411,8 @@ describe('Suite', function() {
     describe('when there is a parent', function() {
       describe('the parent is the root suite', function() {
         it('returns the suite title', function() {
-          var parentSuite = new Suite('');
-          parentSuite.addSuite(this.suite);
+          var rootSuite = new Suite('', {}, true);
+          rootSuite.addSuite(this.suite);
           expect(this.suite.titlePath(), 'to equal', ['A Suite']);
         });
       });