Add data-driven dynamic question mode

api/QuestionsApi.Tests/DynamicQuestionTests.cs

@@ -0,0 +1,71 @@
+using Microsoft.Extensions.Configuration;
+using QuestionsApi.Models;
+using QuestionsApi.Services;
+using Xunit;
+
+namespace QuestionsApi.Tests;
+
+public sealed class DynamicQuestionTests
+{
+    [Fact]
+    public void Generator_IsDeterministic_AndPreservesCorrectAnswer()
+    {
+        var blueprint = Blueprint();
+        var generator = new DynamicQuestionGenerator();
+
+        var first = generator.Generate(blueprint, "same-seed", "one").Question;
+        var second = generator.Generate(blueprint, "same-seed", "two").Question;
+
+        Assert.Equal(first.Stem, second.Stem);
+        Assert.Equal(first.Choices.Select(value => value.Text), second.Choices.Select(value => value.Text));
+        Assert.Equal("correct", first.CorrectChoiceId);
+        Assert.Null(DynamicQuestionGenerator.Validate(blueprint));
+    }
+
+    [Fact]
+    public void SignedTokens_AreUserBound_AndRejectTampering()
+    {
+        var configuration = new ConfigurationBuilder()
+            .AddInMemoryCollection(new Dictionary<string, string?> { ["DynamicQuestions:SigningKey"] = "unit-test-key" })
+            .Build();
+        var service = new DynamicQuestionTokenService(configuration);
+        var claims = new DynamicGenerationClaims
+        {
+            UserId = "user-one",
+            BlueprintExternalId = "test",
+            BlueprintVersion = 1,
+            ObjectiveId = "objective",
+            Seed = "seed",
+            Nonce = "nonce",
+            GeneratorVersion = 1,
+            ExpiresUtc = DateTime.UtcNow.AddMinutes(5)
+        };
+
+        var token = service.SignGeneration(claims);
+
+        Assert.Equal("seed", service.ReadGeneration(token, "user-one").Seed);
+        Assert.Throws<ArgumentException>(() => service.ReadGeneration(token, "user-two"));
+        Assert.ThrowsAny<Exception>(() => service.ReadGeneration(token + "x", "user-one"));
+    }
+
+    private static DynamicQuestionBlueprint Blueprint() => new()
+    {
+        ExternalId = "test",
+        ObjectiveId = "objective",
+        StemTemplate = "Patient age {{age}}.",
+        LeadIn = "What is correct?",
+        Variables = new()
+        {
+            ["age"] = new DynamicVariableDefinition { Minimum = 20, Maximum = 80, Step = 1 }
+        },
+        CorrectAnswer = new DynamicAnswerTemplate { Id = "correct", TextTemplate = "Correct" },
+        Distractors =
+        [
+            new() { Id = "a", TextTemplate = "A" },
+            new() { Id = "b", TextTemplate = "B" },
+            new() { Id = "c", TextTemplate = "C" },
+            new() { Id = "d", TextTemplate = "D" }
+        ],
+        References = [new QuestionReference { Title = "Reference", Url = "https://example.test" }]
+    };
+}