Update validation to return null

* change validate to return null on success as per the docs
* update integration tests to use null for validation success

lib/instance-validator.js

@@ -72,6 +72,8 @@ InstanceValidator.prototype.validate = function() {
   })).then(function() {
     if (self.errors.length) {
       return new sequelizeError.ValidationError(null, self.errors);
+    } else {
+      return null;
     }
   });
 };

test/integration/instance.validations.test.js

@@ -373,7 +373,7 @@ describe(Support.getTestDialectTeaser('InstanceValidator'), function() {
 
       var successfulUser = User.build({ name: '2' });
       return successfulUser.validate().then(function(err) {
-        expect(err).to.be.undefined;
+        expect(err).to.be.null;
       });
     });
   });
@@ -402,7 +402,7 @@ describe(Support.getTestDialectTeaser('InstanceValidator'), function() {
         expect(error.get('name')[0].message).to.equal('Invalid username');
 
         return User.build({ name: 'no error' }).validate().then(function(errors) {
-          expect(errors).to.be.undefined;
+          expect(errors).to.be.null;
         });
       });
     });
@@ -698,14 +698,14 @@ describe(Support.getTestDialectTeaser('InstanceValidator'), function() {
         password: 'short',
         salt: '42'
       }).validate().then(function(errors) {
-        expect(errors).not.to.be.undefined;
+        expect(errors).not.to.be.null;
         expect(errors.get('password')[0].message).to.equal('Please choose a longer password');
       }),
       User.build({
         password: 'loooooooong',
         salt: '42'
       }).validate().then(function(errors) {
-        expect(errors).to.be.undefined;
+        expect(errors).to.be.null;
       })
     ]);
   });
@@ -727,7 +727,7 @@ describe(Support.getTestDialectTeaser('InstanceValidator'), function() {
     return User.build({
       name: 'abcdefg'
     }).validate().then(function(errors) {
-      expect(errors === undefined).to.be.ok;
+      expect(errors).to.be.null;
 
       return User.build({
         name: 'a'

test/unit/instance/build.test.js

@@ -49,7 +49,7 @@ describe(Support.getTestDialectTeaser('Instance'), function() {
       expect(instance.get('updated_time')).to.be.an.instanceof(Date);
 
       return instance.validate().then(function(err) {
-        expect(err).to.be.equal(undefined);
+        expect(err).to.be.equal(null);
       });
     });
 

test/unit/model/validation.test.js

@@ -231,7 +231,7 @@ describe(Support.getTestDialectTeaser('InstanceValidator'), function() {
             });
             var successfulUser = UserSuccess.build({ name: succeedingValue });
             return successfulUser.validate().then(function(errors) {
-              expect(errors).to.be.undefined;
+              expect(errors).to.be.null;
             }).catch(function(err) {
               expect(err).to.deep.equal({});
             });