fix(Suite/Test): untitled suite/test-case mochajs#1632

Throw a user-friendly error when the suite title or the test-case title
isn't provided.

Author: a8m

lib/suite.js

@@ -44,6 +44,9 @@ exports.create = function(parent, title) {
  * @param {Context} parentContext
  */
 function Suite(title, parentContext) {
+  if (!utils.isString(title)) {
+    throw new Error('Suite `title` should be a "string" but "' + typeof title + '" was given instead.');
+  }
   this.title = title;
   function Context() {}
   Context.prototype = parentContext;

lib/test.js

@@ -4,6 +4,7 @@
 
 var Runnable = require('./runnable');
 var create = require('lodash.create');
+var isString = require('./utils').isString;
 
 /**
  * Expose `Test`.
@@ -19,6 +20,9 @@ module.exports = Test;
  * @param {Function} fn
  */
 function Test(title, fn) {
+  if (!isString(title)) {
+    throw new Error('Test `title` should be a "string" but "' + typeof title + '" was given instead.');
+  }
   Runnable.call(this, title, fn);
   this.pending = !fn;
   this.type = 'test';

test/acceptance/throw.js

@@ -7,7 +7,7 @@ describe('a test that throws', function () {
   var suite, runner;
 
   beforeEach(function(){
-    suite = new Suite(null, 'root');
+    suite = new Suite('Suite', 'root');
     runner = new Runner(suite);
   })
 

test/runner.js

@@ -7,7 +7,7 @@ describe('Runner', function(){
   var suite, runner;
 
   beforeEach(function(){
-    suite = new Suite(null, 'root');
+    suite = new Suite('Suite', 'root');
     runner = new Runner(suite);
   })
 

test/suite.js

@@ -393,4 +393,42 @@ describe('Suite', function(){
     });
 
   });
+
+  describe('initialization', function() {
+    it('should throw an error if the title isn\'t a string', function() {
+      (function() {
+        new Suite(undefined, 'root');
+      }).should.throw();
+
+      (function() {
+        new Suite(function(){}, 'root');
+      }).should.throw();
+    });
+
+    it('should not throw if the title is a string', function() {
+      (function() {
+        new Suite('Bdd suite', 'root');
+      }).should.not.throw();
+    });
+  });
 });
+
+describe('Test', function() {
+  describe('initialization', function() {
+    it('should throw an error if the title isn\'t a string', function() {
+      (function() {
+        new Test(function(){});
+      }).should.throw();
+
+      (function() {
+        new Test(undefined, function(){});
+      }).should.throw();
+    });
+
+    it('should not throw if the title is a string', function() {
+      (function() {
+        new Test('test-case',  function(){});
+      }).should.not.throw();
+    });
+  });
+});