# Feature: Quiz System

> **Status**: ⏳ Planned  
> **Priority**: High  
> **Complexity**: High  
> **Estimate**: 6-10 hours  
> **Assignee**: -  
> **Created**: May 31, 2025  
> **Target Completion**: -  
> **PR**: -  
> **Related Features**: Infrastructure Setup, Lesson Management, User Authentication, AI Services (TTS)

---

## 📌 Overview

### Purpose
Implement a comprehensive quiz system that tests users' understanding of lesson material through various question types, with automatic scoring and progress tracking.

### User Story
As a learner, I want to take quizzes after each lesson to test my understanding and receive immediate feedback on my performance.

### Acceptance Criteria
- [ ] Each lesson has an associated quiz
- [ ] Quiz contains 10-15 questions of various types
- [ ] Question types: Multiple Choice, Fill-in-the-Blank, Listening Comprehension, Matching
- [ ] Static difficulty (same questions for all users)
- [ ] 80% passing score required to complete lesson
- [ ] Unlimited retakes allowed
- [ ] Score is recorded in UserProgress table
- [ ] Quiz results show which questions were correct/incorrect

---

## 📋 Requirements

### Functional Requirements
| ID | Requirement | Priority |
|----|-------------|----------|
| FR-001 | Create/Read/Update/Delete quizzes (Admin) | High |
| FR-002 | Associate quizzes with lessons | High |
| FR-003 | Support multiple question types | High |
| FR-004 | Support MCQ questions | High |
| FR-005 | Support fill-in-the-blank questions | High |
| FR-006 | Support listening comprehension questions | High |
| FR-007 | Support matching questions | High |
| FR-008 | Calculate quiz score and passing status | High |
| FR-009 | Record quiz attempts in UserProgress | High |
| FR-010 | Return detailed results with correct/incorrect answers | Medium |
| FR-011 | Allow unlimited retakes | Medium |
| FR-012 | Configurable passing score (default 80%) | Medium |

### Non-Functional Requirements
- Performance: Quiz loading < 300ms
- Performance: Quiz submission < 500ms
- Security: Only authorized admins can create/edit quizzes
- Data Integrity: Quiz-question relationships must be maintained

---

## 🏗️ Technical Design

### Components Involved
- **Backend**: QuizzesController, QuizService, QuestionService
- **Database**: Quizzes, Questions tables
- **Models**: Quiz, Question, QuizDto, QuestionDto, AnswerDto, QuizResult
- **External**: Coqui TTS (for listening questions audio)
- **Frontend**: QuizPage, QuizTab, McqQuestion, FillInBlank, ListeningQuestion, MatchingQuestion components

### Data Flow
```
1. User completes lesson activities
2. User navigates to quiz for the lesson
3. Backend retrieves quiz and questions for the lesson
4. Frontend displays quiz to user
5. User answers all questions
6. Frontend sends answers to backend
7. Backend scores quiz and determines pass/fail
8. Backend updates UserProgress with score and completion status
9. Backend returns detailed results to frontend
10. Frontend displays results with feedback
```

### API Endpoints
| Endpoint | Method | Description | Auth Required |
|----------|--------|-------------|----------------|
| `/api/quizzes` | GET | List all quizzes | Yes |
| `/api/quizzes/{id}` | GET | Get quiz with questions | Yes |
| `/api/lessons/{lessonId}/quiz` | GET | Get quiz for a specific lesson | Yes |
| `/api/quizzes` | POST | Create new quiz (Admin) | Yes |
| `/api/quizzes/{id}` | PUT | Update quiz (Admin) | Yes |
| `/api/quizzes/{id}` | DELETE | Delete quiz (Admin) | Yes |
| `/api/quizzes/{quizId}/questions` | GET | List questions for a quiz | Yes |
| `/api/questions` | POST | Add question to quiz (Admin) | Yes |
| `/api/questions/{id}` | PUT | Update question (Admin) | Yes |
| `/api/questions/{id}` | DELETE | Delete question (Admin) | Yes |
| `/api/quizzes/{quizId}/submit` | POST | Submit quiz answers | Yes |
| `/api/quizzes/{quizId}/results` | GET | Get quiz results history | Yes |

### Database Schema (from application-plan.md)
```sql
-- Quizzes table
CREATE TABLE Quizzes (
    Id SERIAL PRIMARY KEY,
    LessonId INT REFERENCES Lessons(Id) ON DELETE CASCADE,
    PassingScore INT DEFAULT 80
);

-- Questions table
CREATE TABLE Questions (
    Id SERIAL PRIMARY KEY,
    QuizId INT REFERENCES Quizzes(Id) ON DELETE CASCADE,
    Type VARCHAR(20) NOT NULL CHECK (Type IN ('mcq', 'fill_in', 'listening', 'matching')),
    Content TEXT NOT NULL,
    CorrectAnswer TEXT NOT NULL,
    AudioUrl VARCHAR(255),
    Options TEXT[],  -- For MCQ: ['option1', 'option2']
    Points INT DEFAULT 1
);
```

### Question Types

#### 1. Multiple Choice (mcq)
```csharp
{
    Type: "mcq",
    Content: "What is the article for 'Buch'?",
    CorrectAnswer: "das",
    Options: ["der", "die", "das"],
    Points: 1
}
```

#### 2. Fill-in-the-Blank (fill_in)
```csharp
{
    Type: "fill_in",
    Content: "Anna _____ um 7 Uhr auf.",
    CorrectAnswer: "steht",
    Options: null,
    Points: 1
}
```

#### 3. Listening Comprehension (listening)
```csharp
{
    Type: "listening",
    Content: "What did you hear?",
    CorrectAnswer: "This is a book.",
    AudioUrl: "/audio/quiz/1.wav",
    Options: ["This is a book.", "This is a cat."],
    Points: 2  // More points for harder questions
}
```

#### 4. Matching (matching)
```csharp
{
    Type: "matching",
    Content: "Match the word to its article",
    CorrectAnswer: "der",  // For "Buch" in this case
    Options: ["Buch", "Frau", "Kind"],  // Words to match
    Points: 1
}
// Note: Matching questions may need special handling
// Alternative: Store as JSON with pairs
```

---

## 🚀 Implementation Plan

### Phase 1: Database & Models (2-3 hours)
- [ ] Create Quiz entity
- [ ] Create Question entity
- [ ] Create QuizDto, QuestionDto, AnswerDto
- [ ] Create QuizResult model
- [ ] Create IQuizRepository interface
- [ ] Create IQuestionRepository interface
- [ ] Create repository implementations
- [ ] Create migrations for Quizzes and Questions tables

### Phase 2: Backend Services (2-3 hours)
- [ ] Create QuizService with CRUD operations
- [ ] Create QuestionService with CRUD operations
- [ ] Create QuizSubmissionService for handling answers
- [ ] Implement scoring logic
- [ ] Implement pass/fail determination
- [ ] Update UserProgress on quiz completion
- [ ] Create mapping between entities and DTOs

### Phase 3: API Controllers (2 hours)
- [ ] Create QuizzesController
- [ ] Create QuestionsController
- [ ] Implement quiz submission endpoint
- [ ] Implement results endpoint
- [ ] Add authorization (Admin for write operations)
- [ ] Add validation for quiz data

### Phase 4: Question Type Implementation (2 hours)
- [ ] Implement MCQ question handling
- [ ] Implement fill-in-the-blank question handling
- [ ] Implement listening comprehension with audio
- [ ] Implement matching question handling
- [ ] Add audio generation for listening questions

### Phase 5: Frontend Integration (2 hours)
- [ ] Create QuizPage component
- [ ] Create QuizTab component
- [ ] Create McqQuestion component
- [ ] Create FillInBlank component
- [ ] Create ListeningQuestion component
- [ ] Create MatchingQuestion component
- [ ] Create QuizResults component
- [ ] Add quiz to LessonPage

### Milestones
| Milestone | Date | Status |
|-----------|------|--------|
| Database & Models | - | ⏳ |
| Backend Services | - | ⏳ |
| API Controllers | - | ⏳ |
| Question Type Implementation | - | ⏳ |
| Frontend Integration | - | ⏳ |

---

## ✅ Tasks

### Backend
- [ ] Create Domain/Entities/Quiz.cs
- [ ] Create Domain/Entities/Question.cs
- [ ] Create Application/DTOs/QuizDto.cs
- [ ] Create Application/DTOs/QuestionDto.cs
- [ ] Create Application/DTOs/AnswerDto.cs
- [ ] Create Application/DTOs/QuizResult.cs
- [ ] Create Domain/Interfaces/IQuizRepository.cs
- [ ] Create Domain/Interfaces/IQuestionRepository.cs
- [ ] Create Infrastructure/Data/Repositories/QuizRepository.cs
- [ ] Create Infrastructure/Data/Repositories/QuestionRepository.cs
- [ ] Create Application/Services/QuizService.cs
- [ ] Create Application/Services/QuestionService.cs
- [ ] Create Application/Services/QuizSubmissionService.cs
- [ ] Create Presentation/Controllers/QuizzesController.cs
- [ ] Create Presentation/Controllers/QuestionsController.cs
- [ ] Integrate with UserProgress from Lesson Management
- [ ] Register services in Program.cs
- [ ] Write unit tests for services
- [ ] Write integration tests for controllers

### Database
- [ ] Create migration for Quizzes table
- [ ] Create migration for Questions table
- [ ] Add foreign key from Quizzes to Lessons
- [ ] Add indexes for QuizId, Type
- [ ] Apply migrations

### Audio Generation
- [ ] Extend Coqui TTS service for quiz questions
- [ ] Generate audio for listening comprehension questions
- [ ] Store audio files with quiz question IDs

### Question Types
- [ ] Implement MCQ answer validation
- [ ] Implement fill-in-the-blank answer validation
- [ ] Implement listening comprehension answer validation
- [ ] Implement matching answer validation
- [ ] Add case-insensitive comparison where appropriate
- [ ] Add whitespace trimming for answers

### Frontend
- [ ] Create pages/QuizPage.tsx
- [ ] Create components/QuizTab.tsx
- [ ] Create components/questions/McqQuestion.tsx
- [ ] Create components/questions/FillInBlank.tsx
- [ ] Create components/questions/ListeningQuestion.tsx
- [ ] Create components/questions/MatchingQuestion.tsx
- [ ] Create components/QuizResults.tsx
- [ ] Create hooks/useQuiz.ts
- [ ] Integrate AudioPlayer for listening questions
- [ ] Add quiz timer (optional)
- [ ] Add progress indicator

---

## 🔗 Dependencies

### Feature Dependencies
- [Infrastructure Setup](infrastructure-setup.md) - Required
- [Lesson Management](lesson-management.md) - Required (quizzes associated with lessons)
- [User Authentication](user-authentication.md) - Required (for tracking progress)
- [AI Services - TTS](ai-services.md) - Required (for listening question audio)

### Technical Dependencies
- Entity Framework Core
- AutoMapper (optional)

### Blockers
- [ ] Infrastructure Setup must be complete
- [ ] Lesson Management must be complete
- [ ] User Authentication must be complete for progress tracking

---

## ✅ Definition of Done

### General Criteria (All Features)
- [ ] All acceptance criteria met and verified
- [ ] All tasks in this document completed
- [ ] Code follows Clean Architecture principles
- [ ] Code reviewed and approved by at least 1 team member
- [ ] All tests passing (unit, integration)
- [ ] Documentation updated (README, AGENTS.md if applicable)
- [ ] Feature works in development environment
- [ ] Feature deployed to staging environment
- [ ] Performance meets defined targets
- [ ] Security review completed
- [ ] No critical bugs or blockers

### Quiz-Specific Criteria
- [ ] Quizzes can be created, read, updated, and deleted
- [ ] Questions can be added to, updated in, and removed from quizzes
- [ ] All question types work correctly (MCQ, Fill-in, Listening, Matching)
- [ ] Quiz submission works and returns score
- [ ] Pass/fail determination is correct (80% threshold)
- [ ] User progress is updated on quiz completion
- [ ] Quiz results show correct/incorrect answers
- [ ] Unlimited retakes are allowed
- [ ] Audio for listening questions is generated and accessible

---

## 🧪 Testing Strategy

### Testing Approach

| Test Type | Coverage | Tools | Responsibility |
|-----------|----------|-------|----------------|
| Unit Tests | 80%+ code coverage | MsTest, Moq | Backend Dev |
| Integration Tests | All service interactions | MsTest, TestContainers | Backend Dev |
| API Tests | All endpoints | MsTest, HttpClient | Backend Dev |
| Frontend Unit Tests | Component logic | Vitest | Frontend Dev |
| Frontend Integration | Service integration | Vitest | Frontend Dev |
| E2E Tests | Critical user journeys | Playwright | QA/Dev |
| Manual Testing | Exploratory, edge cases | BrowserStack | QA |

### Quiz-Specific Tests

#### Backend Tests
- [ ] Create quiz → success
- [ ] Create quiz with invalid lesson → error
- [ ] Get quiz by ID → returns correct quiz with questions
- [ ] Get quiz by lesson → returns correct quiz
- [ ] Add question to quiz → success
- [ ] Add MCQ question → success
- [ ] Add fill-in question → success
- [ ] Add listening question → success
- [ ] Add matching question → success
- [ ] Update question → success
- [ ] Delete question → success
- [ ] Submit quiz with all correct answers → 100% score
- [ ] Submit quiz with some correct answers → partial score
- [ ] Submit quiz with all wrong answers → 0% score
- [ ] Submit quiz with passing score → user progress updated
- [ ] Submit quiz with failing score → user progress not updated
- [ ] Delete quiz → cascades to questions

#### Question Type Tests
- [ ] MCQ: Correct answer → scored correctly
- [ ] MCQ: Incorrect answer → scored incorrectly
- [ ] Fill-in: Exact match → scored correctly
- [ ] Fill-in: Case-insensitive match → scored correctly
- [ ] Fill-in: Whitespace variation → scored correctly
- [ ] Fill-in: Close but wrong → scored incorrectly
- [ ] Listening: Correct transcription → scored correctly
- [ ] Listening: Incorrect transcription → scored incorrectly
- [ ] Matching: All pairs correct → scored correctly
- [ ] Matching: Some pairs correct → partial score

#### Business Logic Tests
- [ ] Scoring with default points → correct calculation
- [ ] Scoring with custom points → correct calculation
- [ ] Pass/fail at 80% threshold → correct determination
- [ ] Pass/fail at exactly 80% → passes
- [ ] Pass/fail at 79% → fails
- [ ] User progress updates on first pass → lesson marked complete
- [ ] User progress updates on subsequent pass → no change (already complete)

---

## 📝 Notes & Decisions

### Decisions Made
| Date | Decision | Rationale |
|------|----------|-----------|
| May 31, 2025 | Static difficulty | Simpler implementation, consistent experience for all users |
| May 31, 2025 | 80% passing score | Industry standard, rigorous but achievable |
| May 31, 2025 | Unlimited retakes | Encourages practice, reduces anxiety |
| May 31, 2025 | Multiple question types | Varied testing, caters to different learning styles |
| May 31, 2025 | Store AudioUrl on questions | Enables listening comprehension questions |

### Technical Notes
- Questions table uses PostgreSQL TEXT[] array type for Options
- Each question has a Points value for weighted scoring
- Quiz.PassingScore is the percentage required (default 80)
- QuizResult should include: Passed, Score, TotalPoints, QuestionResults[]
- QuestionResults should include: QuestionId, UserAnswer, CorrectAnswer, IsCorrect, PointsEarned

### Question Type Validation Logic

#### MCQ
- UserAnswer must exactly match one of the Options
- Case-insensitive comparison recommended

#### Fill-in-the-Blank
- UserAnswer compared to CorrectAnswer
- Trim whitespace from both before comparison
- Case-insensitive comparison recommended
- Consider allowing minor variations (e.g., "steht" vs "stehen")

#### Listening Comprehension
- UserAnswer must exactly match CorrectAnswer (or one of Options for MCQ-style listening)
- AudioUrl must be present and valid

#### Matching
- Need to handle multiple pairs
- Consider storing as: `{ pairs: [{left: "Buch", right: "das"}, ...] }`
- Validate that all pairs are correct

### Gotchas
- ⚠️ Listening questions require audio generation - can be slow
- ⚠️ Fill-in-the-blank needs careful validation (accents, case, etc.)
- ⚠️ Matching questions need special data structure
- ⚠️ Quiz deletion must cascade to Questions (ON DELETE CASCADE)
- ⚠️ Question updates must maintain quiz integrity

---

## 📊 Progress History

| Date | Status Change | Notes |
|------|---------------|-------|
| May 31, 2025 | Created | Initial plan based on application-plan.md |

---

## 📎 Related Files & Links

- Architecture: [Backend Structure](../architecture/backend-structure.md)
- Architecture: [Application Plan](../architecture/application-plan.md)
- Database Schema: [Initial Database Schema](../database/initial-database-schema.sql)
- Feature: [Lesson Management](lesson-management.md)
- Feature: [User Authentication](user-authentication.md)
- Feature: [AI Services](ai-services.md)

---

*Feature created from application-plan.md*