Initial commit: standalone quiz-testing system

Full-stack F# (Domain/Server/Client via Fable+Elmish+Feliz), PostgreSQL
persistence via Dapper, Docker Compose deployment. Student quiz-taking flow
with time-limit enforcement and focus-loss tracking, Teacher question bank
and quiz builder with results analytics, Admin user management.

tests/Domain.Tests/GradingTests.fs

@@ -0,0 +1,182 @@
+module Domain.Tests.GradingTests
+
+open System
+open Xunit
+open Domain
+
+let private optA = { Id = OptionId(Guid.NewGuid()); Text = "A" }
+let private optB = { Id = OptionId(Guid.NewGuid()); Text = "B" }
+let private optC = { Id = OptionId(Guid.NewGuid()); Text = "C" }
+
+let private newQuestionId () = QuestionId(Guid.NewGuid())
+
+[<Fact>]
+let ``single choice: correct option awards full points`` () =
+    let qId = newQuestionId ()
+    let qType = SingleChoice([ optA; optB; optC ], optB.Id)
+    let grade = Grading.gradeResponse qId qType 10.0 (SingleChoiceResponse(Some optB.Id))
+    Assert.True grade.IsCorrect
+    Assert.Equal(10.0, grade.PointsAwarded)
+
+[<Fact>]
+let ``single choice: wrong option awards zero`` () =
+    let qId = newQuestionId ()
+    let qType = SingleChoice([ optA; optB; optC ], optB.Id)
+    let grade = Grading.gradeResponse qId qType 10.0 (SingleChoiceResponse(Some optA.Id))
+    Assert.False grade.IsCorrect
+    Assert.Equal(0.0, grade.PointsAwarded)
+
+[<Fact>]
+let ``single choice: unanswered awards zero`` () =
+    let qId = newQuestionId ()
+    let qType = SingleChoice([ optA; optB ], optB.Id)
+    let grade = Grading.gradeResponse qId qType 10.0 (SingleChoiceResponse None)
+    Assert.False grade.IsCorrect
+
+[<Fact>]
+let ``multiple choice: exact set match is correct`` () =
+    let qId = newQuestionId ()
+    let correct = Set.ofList [ optA.Id; optC.Id ]
+    let qType = MultipleChoice([ optA; optB; optC ], correct)
+    let grade = Grading.gradeResponse qId qType 5.0 (MultipleChoiceResponse(Set.ofList [ optA.Id; optC.Id ]))
+    Assert.True grade.IsCorrect
+
+[<Fact>]
+let ``multiple choice: partial selection is incorrect`` () =
+    let qId = newQuestionId ()
+    let correct = Set.ofList [ optA.Id; optC.Id ]
+    let qType = MultipleChoice([ optA; optB; optC ], correct)
+    let grade = Grading.gradeResponse qId qType 5.0 (MultipleChoiceResponse(Set.ofList [ optA.Id ]))
+    Assert.False grade.IsCorrect
+
+[<Fact>]
+let ``true false: matching answer is correct`` () =
+    let qId = newQuestionId ()
+    let grade = Grading.gradeResponse qId (TrueFalse true) 2.0 (TrueFalseResponse(Some true))
+    Assert.True grade.IsCorrect
+
+[<Fact>]
+let ``short answer: case-insensitive match by default`` () =
+    let qId = newQuestionId ()
+    let qType = ShortAnswer([ "Paris" ], caseSensitive = false)
+    let grade = Grading.gradeResponse qId qType 3.0 (ShortAnswerResponse "  paris ")
+    Assert.True grade.IsCorrect
+
+[<Fact>]
+let ``short answer: case-sensitive rejects mismatched case`` () =
+    let qId = newQuestionId ()
+    let qType = ShortAnswer([ "Paris" ], caseSensitive = true)
+    let grade = Grading.gradeResponse qId qType 3.0 (ShortAnswerResponse "paris")
+    Assert.False grade.IsCorrect
+
+[<Fact>]
+let ``numeric: within tolerance is correct`` () =
+    let qId = newQuestionId ()
+    let qType = Numeric(3.14, 0.01)
+    let grade = Grading.gradeResponse qId qType 4.0 (NumericResponse(Some 3.145))
+    Assert.True grade.IsCorrect
+
+[<Fact>]
+let ``numeric: outside tolerance is incorrect`` () =
+    let qId = newQuestionId ()
+    let qType = Numeric(3.14, 0.01)
+    let grade = Grading.gradeResponse qId qType 4.0 (NumericResponse(Some 3.2))
+    Assert.False grade.IsCorrect
+
+let private sampleQuiz (questionRefs: QuizQuestionRef list) : Quiz =
+    { Id = QuizId(Guid.NewGuid())
+      OwnerId = UserId(Guid.NewGuid())
+      Title = "Sample quiz"
+      Description = ""
+      TimeLimit = None
+      MaxAttempts = None
+      GradingMethod = HighestAttempt
+      ShuffleQuestions = false
+      ShuffleAnswers = false
+      OpenFrom = None
+      OpenTo = None
+      PassingScore = None
+      QuestionSources = questionRefs |> List.map FixedQuestion
+      AssignedStudentIds = Set.empty }
+
+[<Fact>]
+let ``gradeAttempt: unanswered questions score zero without crashing`` () =
+    let qId = newQuestionId ()
+    let question =
+        { Id = qId
+          TopicId = TopicId(Guid.NewGuid())
+          Text = "2 + 2 = ?"
+          Points = 5.0
+          Type = Numeric(4.0, 0.0) }
+
+    let refs = [ { QuestionId = qId; Points = 5.0; Order = 0 } ]
+    let quiz = sampleQuiz refs
+    let questions = Map.ofList [ qId, question ]
+
+    let attempt =
+        Attempt.start (AttemptId(Guid.NewGuid())) quiz refs (UserId(Guid.NewGuid())) DateTimeOffset.UtcNow
+
+    let graded = Grading.gradeAttempt questions attempt
+
+    Assert.Equal(Some 0.0, graded.Score)
+    Assert.Equal(Graded, graded.State)
+
+[<Fact>]
+let ``gradeAttempt: sums points across multiple questions`` () =
+    let q1Id, q2Id = newQuestionId (), newQuestionId ()
+
+    let q1 =
+        { Id = q1Id
+          TopicId = TopicId(Guid.NewGuid())
+          Text = "Is the sky blue?"
+          Points = 1.0
+          Type = TrueFalse true }
+
+    let q2 =
+        { Id = q2Id
+          TopicId = TopicId(Guid.NewGuid())
+          Text = "Capital of France?"
+          Points = 1.0
+          Type = ShortAnswer([ "Paris" ], false) }
+
+    let refs =
+        [ { QuestionId = q1Id; Points = 3.0; Order = 0 }
+          { QuestionId = q2Id; Points = 7.0; Order = 1 } ]
+
+    let quiz = sampleQuiz refs
+    let questions = Map.ofList [ q1Id, q1; q2Id, q2 ]
+
+    let attempt =
+        Attempt.start (AttemptId(Guid.NewGuid())) quiz refs (UserId(Guid.NewGuid())) DateTimeOffset.UtcNow
+        |> Attempt.recordResponse q1Id (TrueFalseResponse(Some true))
+        |> Attempt.recordResponse q2Id (ShortAnswerResponse "paris")
+
+    let graded = Grading.gradeAttempt questions attempt
+
+    Assert.Equal(Some 10.0, graded.Score)
+
+[<Fact>]
+let ``applyGradingMethod: HighestAttempt picks the best score`` () =
+    let mkAttempt score started =
+        { Id = AttemptId(Guid.NewGuid())
+          QuizId = QuizId(Guid.NewGuid())
+          UserId = UserId(Guid.NewGuid())
+          StartedAt = started
+          SubmittedAt = Some started
+          State = Graded
+          Questions = []
+          Responses = Map.empty
+          Grades = Map.empty
+          Score = Some score
+          FocusLossCount = 0 }
+
+    let now = DateTimeOffset.UtcNow
+    let attempts = [ mkAttempt 4.0 now; mkAttempt 9.0 (now.AddMinutes 1.0); mkAttempt 6.0 (now.AddMinutes 2.0) ]
+
+    let result = Grading.applyGradingMethod HighestAttempt attempts
+    Assert.Equal(Some 9.0, result |> Option.bind (fun a -> a.Score))
+
+[<Fact>]
+let ``applyGradingMethod: no graded attempts returns None`` () =
+    let result = Grading.applyGradingMethod HighestAttempt []
+    Assert.Equal(None, result)