Added support for 'to have no children' HTMLElement assertion

lib/index.js

@@ -114,7 +114,7 @@ module.exports = {
       }
     });
 
-    expect.addAssertion('HTMLElement', ['to [only] have (attribute|attributes)'], function (expect, subject, cmp) {
+    expect.addAssertion('HTMLElement', 'to [only] have (attribute|attributes)', function (expect, subject, cmp) {
       var attrs = getAttributes(subject);
 
       if (typeof cmp === 'string') {
@@ -127,5 +127,15 @@ module.exports = {
         expect(attrs, 'to [exhaustively] satisfy', cmp);
       }
     });
+
+    expect.addAssertion('HTMLElement', 'to have [no] (child|children)', function (expect, subject, query, cmp) {
+      if (this.flags.no) {
+        this.errorMode = 'nested';
+        return expect(Array.prototype.slice.call(subject.childNodes), 'to be an empty array');
+      } else {
+        var children = Array.prototype.slice.call(subject.querySelectorAll(query));
+        throw children;
+      }
+    });
   }
 };

test/unexpected-dom.js

@@ -157,4 +157,42 @@ describe('unexpected-dom', function () {
     });
   });
 
+  describe('to have children', function () {
+    describe('with no children flag', function () {
+      it('should match element with no children', function () {
+        this.body.innerHTML = '<div></div>';
+        var el = this.body.firstChild;
+
+        expect(el, 'to have no children');
+      });
+
+      it('should fail on element with HTMLElement children', function () {
+        this.body.innerHTML = '<div><p></p></div>';
+        var el = this.body.firstChild;
+
+        expect(function () {
+          expect(el, 'to have no children');
+        }, 'to throw', /^expected <div >...<\/div> to have no children/);
+      });
+
+      it('should fail on element with HTMLComment children', function () {
+        this.body.innerHTML = '<div><!-- Comment --></div>';
+        var el = this.body.firstChild;
+
+        expect(function () {
+          expect(el, 'to have no children');
+        }, 'to throw', /^expected <div \/> to have no children/);
+      });
+
+      it('should fail on element with TextNode children', function () {
+        this.body.innerHTML = '<div>I am a text</div>';
+        var el = this.body.firstChild;
+
+        expect(function () {
+          expect(el, 'to have no children');
+        }, 'to throw', /^expected <div \/> to have no children/);
+      });
+    });
+  });
+
 });