public async Task AddNewRangeAsync_WithDuplicates_DuplicatesAreNotAdded() { const string duplicatePath = "a"; var uploadList = new UploadList(_helpers) { new UploadFile { FullPath = duplicatePath }, new UploadFile { FullPath = "b" }, }; var addFiles = new List <string> { duplicatePath, "c" }; await uploadList.AddNewRangeAsync(addFiles); Assert.That(uploadList.Count, Is.EqualTo(3)); Assert.That(uploadList.Count(x => x.FullPath == duplicatePath), Is.EqualTo(1)); }