public void TestOpenBrowser()
        {
            const string targetUrl       = "http://target/url";
            var          objectUnderTest = new TestTopicViewModelBase(
                _ownerMock.Object, _itemMock.Object, new List <Subscription>());

            objectUnderTest.OpenBrowser(targetUrl);

            _ownerMock.Verify(o => o.OpenBrowser(targetUrl), Times.Once);
        }