Fixing some tests

test/GitHub.App.UnitTests/ViewModels/GitHubPane/IssueListViewModelBaseTests.cs

@@ -1,8 +1,13 @@
 using System;
 using System.Collections.Generic;
+using System.Globalization;
 using System.Linq;
+using System.Reactive;
 using System.Reactive.Linq;
+using System.Reactive.Subjects;
+using System.Reactive.Threading.Tasks;
 using System.Threading.Tasks;
+using GitHub;
 using GitHub.Collections;
 using GitHub.Models;
 using GitHub.Primitives;
@@ -176,7 +181,7 @@ public Target(IRepositoryService repositoryService, int itemCount)
 
             protected override Task<IVirtualizingListSource<IIssueListItemViewModelBase>> CreateItemSource(bool refresh)
             {
-                throw new NotImplementedException();
+                return Task.FromResult(Substitute.For<IVirtualizingListSource<IIssueListItemViewModelBase>>());
             }
 
             protected override Task DoOpenItem(IIssueListItemViewModelBase item)