public void long_interval_for_easy_cards()
        {
            var difficultyRating = DifficultyRating.Easiest;
            var daysSincePreviousReview = 11;
            var item = new ReviewItemBuilder()
                                .WithLastReviewDate(_clock.Now().AddDays(-1))
                                .WitPreviousReviewDate(daysSincePreviousReview)
                                .WithDifficultyRating(difficultyRating)
                                .WithCorrectReviewStreak(3)
                                .Build();
            var strategy = new SuperMemo2ReviewStrategy(_clock);

            var nextReview = strategy.NextReview(item);

            var expectedInterval = (daysSincePreviousReview - 1) * strategy.DifficultyRatingToEasinessFactor(difficultyRating);
            Assert.That(nextReview, Is.EqualTo(item.ReviewDate.AddDays(expectedInterval)));
        }