Prefer high-performing distractors

2026-07-20 02:44:58 -05:00
parent dae3a31b71
commit 121e80b2ea
6 changed files with 152 additions and 20 deletions
@@ -35,6 +35,41 @@ public sealed class ChoicePoolTests
        Assert.Single(response.ReviewFollowups);
    }

+    [Fact]
+    public void HigherSelectionRatesIncreaseDistractorPresentationFrequency()
+    {
+        var question = BuildQuestion(9);
+        var rates = question.Choices.ToDictionary(choice => choice.Id, _ => 0);
+        rates["B"] = 100;
+        var random = new Random(12345);
+        var counts = question.Choices.ToDictionary(choice => choice.Id, _ => 0);
+
+        for (var iteration = 0; iteration < 2000; iteration++)
+        {
+            foreach (var id in ChoicePoolSelector.SelectChoiceIds(question, rates, random))
+                counts[id]++;
+        }
+
+        Assert.All(question.Choices.Where(choice => choice.Id is not "A" and not "B"),
+            choice => Assert.True(counts["B"] > counts[choice.Id]));
+        Assert.Equal(2000, counts["A"]);
+    }
+
+    [Fact]
+    public void MissingSelectionRatesStillAllowDifferentDistractorSets()
+    {
+        var question = BuildQuestion(9);
+        var random = new Random(9876);
+        var sets = Enumerable.Range(0, 40)
+            .Select(_ => string.Join(",", ChoicePoolSelector.SelectChoiceIds(
+                question,
+                new Dictionary<string, int>(),
+                random).Order()))
+            .ToHashSet();
+
+        Assert.True(sets.Count > 1);
+    }
+
    [Fact]
    public void ExamReviewContainsOnlyChoicesPresentedDuringTheExam()
    {