public async Task SortAndSaveNumbers_shouldReturnSortedtring(string input, string expected)
{
const string fileName = "file01.txt";
var mockFileService = new Mock <IFileService>();
mockFileService
.Setup(f => f.SaveToFile(It.IsAny <string>()))
.ReturnsAsync(fileName);
var sortingService = new SortingService(mockFileService.Object);
SavedData result = await sortingService.Create(new SortingInput { Line = input });
Assert.Equal(expected, result.OrderedNumbers);
Assert.Equal(fileName, result.FileName);
}