public void IsValid_GivenCollectionWithWithoutAllCellsWithValues1to9_ReturnFalse() { var sut = new CellCollection(""); sut.Cells.Add(TestUtilities.CreateCell(1)); sut.Cells.Add(TestUtilities.CreateCell(2)); sut.Cells.Add(TestUtilities.CreateCell(3)); sut.Cells.Add(TestUtilities.CreateCell(4)); sut.Cells.Add(TestUtilities.CreateCell(6)); sut.Cells.Add(TestUtilities.CreateCell(7)); sut.Cells.Add(TestUtilities.CreateCell(9)); var result = sut.IsValid(); Assert.IsFalse(result); }