Write Unit Tests in Java

Noom's habit tracker shows users a "day streak" for logging meals. Support has tickets saying streaks sometimes jump or reset incorrectly. Here is the class that computes the streak from a user's log dates:

public class StreakCalculator {
    public int calculateStreak(List<LocalDate> logDates) {
        Collections.sort(logDates);
        int streak = 1;
        LocalDate previous = logDates.get(0);

        for (int i = 1; i < logDates.size(); i++) {
            LocalDate current = logDates.get(i);
            long gap = ChronoUnit.DAYS.between(previous, current);

            if (gap <= 1) {
                streak++;
            } else {
                streak = 1;
            }

            if (current == previous) {
                streak--;
            }

            previous = current;
        }

        return streak;
    }
}

As the QA engineer on this feature, write the unit tests you would add for this class. For each test, say what input it uses, what defect in the code it would catch, and what the test would assert instead of what the current code produces.