public void TestAddRemove() { _dataSource.Setup(x => x.SelectedLogLines).Returns(new HashSet <LogLineIndex> { 13 }); var logFile = new InMemoryLogFile(); logFile.AddEmptyEntries(13); _dataSource.Setup(x => x.FilteredLogFile).Returns(logFile); _viewModel.CurrentDataSource = _dataSource.Object; _viewModel.AddBookmarkCommand.Execute(null); _viewModel.Bookmarks.Should().NotBeEmpty(); var bookmark = _viewModel.Bookmarks.First(); bookmark.RemoveCommand.Execute(null); _viewModel.Bookmarks.Should().BeEmpty(); }