Quiz App - Backend API

REST API for a quiz application that allows users to practice programming knowledge through multiple-choice questions on various topics (HTML, CSS, JavaScript, Python, PHP, etc.).

Technology Stack

Layer	Technology
Framework	.NET 9 / ASP.NET Core Web API
Database	SQL Server + Entity Framework Core
Authentication	ASP.NET Core Identity + JWT Bearer
Validation	FluentValidation
Documentation	Swagger / OpenAPI
Testing	xUnit + FsCheck (property-based testing)

Prerequisites

• .NET 9 SDK
• SQL Server (LocalDB, Express, or Developer Edition)
• EF Core CLI Tools

Installing EF Core CLI

dotnet tool install --global dotnet-ef

Configuration

Connection String

Edit src/QuizApp/appsettings.json with your SQL Server connection string:

{
  "ConnectionStrings": {
    "DefaultConnection": "Server=(localdb)\\mssqllocaldb;Database=QuizAppDb;Trusted_Connection=True;MultipleActiveResultSets=true"
  }
}

JWT (Authentication)

JWT settings are in appsettings.json. For production, change the secret key:

{
  "Jwt": {
    "Key": "YourSecretKeyHere_AtLeast32Characters!",
    "Issuer": "QuizApp",
    "Audience": "QuizApp",
    "ExpirationInMinutes": 60
  }
}

CORS

The Angular frontend is allowed by default at http://localhost:4200:

{
  "Cors": {
    "FrontendUrl": "http://localhost:4200"
  }
}

Getting Started

1. Create the database

From the backend/src/QuizApp directory:

dotnet ef migrations add InitialCreate
dotnet ef database update

2. Run the application

dotnet run --project src/QuizApp

The API will be available at https://localhost:7013 (or http://localhost:5276).

3. Access Swagger

Open in your browser: https://localhost:7013/swagger

Running Tests

From the backend directory:

dotnet test

Tests include:

• Unit tests — Controllers, Services, Validators
• Property-based tests (FsCheck) — 13 formal correctness properties

Project Structure

backend/
├── QuizApp.sln
├── src/
│   └── QuizApp/
│       ├── Controllers/       # API Controllers (Auth, Quiz, Session, Dashboard)
│       ├── Data/              # DbContext and EF Core configurations
│       ├── DTOs/              # Data Transfer Objects
│       ├── Exceptions/        # Custom exceptions (404, 409, 401, 400)
│       ├── Middleware/        # Global Exception Handler
│       ├── Models/            # Domain entities
│       ├── Services/          # Service layer (business logic)
│       ├── Validators/        # FluentValidation validators
│       └── Program.cs         # Configuration and startup
└── tests/
    └── QuizApp.Tests/
        ├── Controllers/       # Controller tests
        ├── Middleware/        # Middleware tests
        ├── PropertyTests/     # Property-based tests (FsCheck)
        ├── Services/          # Service tests
        └── Validators/        # Validation tests

API Endpoints

Authentication

Method	Route	Description	Auth Required
POST	/api/auth/register	Register a new user	No
POST	/api/auth/login	Authenticate user	No

Quizzes

Method	Route	Description	Auth Required
GET	/api/quizzes	List all quizzes	No
GET	/api/quizzes/{id}	Get quiz details	No
POST	/api/quizzes	Create a quiz	Yes
PUT	/api/quizzes/{id}	Update a quiz	Yes
DELETE	/api/quizzes/{id}	Delete a quiz	Yes

Quiz Sessions

Method	Route	Description	Auth Required
POST	/api/quizzes/{quizId}/sessions	Start a session	No
POST	/api/sessions/{sessionId}/answers	Submit an answer	No
POST	/api/sessions/{sessionId}/complete	Complete session	No
GET	/api/sessions/{sessionId}/result	Get result	No

Dashboard

Method	Route	Description	Auth Required
GET	/api/dashboard	Get user's quiz history	Yes

Features

• Authentication & Registration — JWT with Identity, minimum 8-character password
• Quiz CRUD — Create, read, update, and delete quizzes (protected by authentication)
• Quiz Sessions — Start, submit answers, complete with result calculation
• Result Calculation — Correct answer count, elapsed time, pass/fail determination (≥70%)
• Guest Access — Users can take quizzes without creating an account
• Dashboard — Complete history of all attempts for authenticated users
• Validation — Each question must have exactly 4 options with exactly 1 correct
• Error Handling — Global middleware with consistent JSON error responses
• Duplicate Prevention — Cannot answer the same question twice in a session

Correctness Properties (Property-Based Tests)

#	Property	Description
1	Question Structure Invariant	Every question has exactly 4 options with 1 correct
4	Answer Persistence Round-Trip	Stored answers contain the exact IDs submitted
5	Elapsed Time Calculation	Elapsed time = completedAt - startedAt
6	Correct Answer Count	Correct count = number of answers where isCorrect=true
7	Pass/Fail Threshold	Pass if and only if correctAnswers/total ≥ 0.70
8	Quiz List Completeness	List returns all quizzes with correct question counts
10	Password Length Validation	Passwords < 8 chars rejected, ≥ 8 chars accepted
11	Dashboard Chronological Ordering	Sessions sorted by completion date descending
12	Repeat Attempt Preservation	K completions = K records on dashboard
13	Guest Session Non-Association	Guest sessions have null userId and calculable results

License

This project is licensed under the MIT License.