MortageScience.cs

public MortgageResult ApplyForMortgage(MortgageApplication app) {
  var oldProcessor = new LegacyProcessor(EmailFacade.Instance);
  var newProcessor = new ExperimentalProcessor(new FakeEmailSender()); // or null potentially
  
  return Scientist.Science<MortgageResult>(
    "Side effects are bad",
    experiment =>
    {
        experiment.Use(() => oldProcessor.Analyze(app));
        experiment.Try(() => newProcessor.Analyze(app));
        experiment.Compare((x, y) => x.Score == y.Score);
    });
}