public async Task SaveShouldWriteToDisk()
{
var subject = Arrange();
this.mockReaderWriter.Setup(m => m.WriteToDiskAsync(It.IsAny<string>(), It.IsAny<string>())).Returns(Task.CompletedTask);
SetPrivateBudgetCollection(subject);
await subject.SaveAsync();
this.mockReaderWriter.VerifyAll();
}