DeutschLernen/Tests/Unit/Application/Services/LessonServiceTests.cs

using System;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;
using GermanApp.Application.DTOs;
using GermanApp.Application.Services;
using GermanApp.Domain.Entities;
using GermanApp.Domain.Interfaces;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using Moq;

namespace GermanApp.Tests.Unit.Application.Services;

[TestClass]
public class LessonServiceTests
{
    private Mock<ILessonRepository> _mockLessonRepo;
    private Mock<ILevelRepository> _mockLevelRepo;
    private LessonService _service;

    [TestInitialize]
    public void Setup()
    {
        _mockLessonRepo = new Mock<ILessonRepository>();
        _mockLevelRepo = new Mock<ILevelRepository>();
        _service = new LessonService(_mockLessonRepo.Object, _mockLevelRepo.Object);
    }

    [TestMethod]
    public async Task GetAllLessonsAsync_ReturnsMappedDtoList()
    {
        var lessons = new List<Lesson> { Lesson.Create(1, "Test", 1, "Topic", "Desc") };
        _mockLessonRepo.Setup(r => r.GetAllAsync(It.IsAny<CancellationToken>()))
            .ReturnsAsync(lessons);

        var result = await _service.GetAllLessonsAsync();

        Assert.AreEqual(1, result.Count);
        Assert.AreEqual("Test", result[0].Title);
    }

    [TestMethod]
    public async Task GetLessonByIdAsync_WithExistingId_ReturnsLesson()
    {
        var lesson = Lesson.Create(1, "Test", 1, "Topic", "Desc");
        _mockLessonRepo.Setup(r => r.GetByIdAsync(1, It.IsAny<CancellationToken>()))
            .ReturnsAsync(lesson);

        var result = await _service.GetLessonByIdAsync(1);

        Assert.IsNotNull(result);
        Assert.AreEqual("Test", result.Title);
    }

    [TestMethod]
    public async Task GetLessonByIdAsync_WithNonExistingId_ReturnsNull()
    {
        _mockLessonRepo.Setup(r => r.GetByIdAsync(999, It.IsAny<CancellationToken>()))
            .ReturnsAsync((Lesson?)null);

        var result = await _service.GetLessonByIdAsync(999);

        Assert.IsNull(result);
    }

    [TestMethod]
    public async Task GetLessonsByLevelAsync_ReturnsFilteredLessons()
    {
        var lessons = new List<Lesson> { Lesson.Create(1, "L1", 1, "T1", "D1") };
        _mockLessonRepo.Setup(r => r.GetByLevelAsync(1, It.IsAny<CancellationToken>()))
            .ReturnsAsync(lessons);

        var result = await _service.GetLessonsByLevelAsync(1);

        Assert.AreEqual(1, result.Count);
        Assert.AreEqual("L1", result[0].Title);
    }

    [TestMethod]
    public async Task CreateLessonAsync_WithValidDtoAndValidLevel_CreatesLesson()
    {
        var level = Level.Create("A1", "A1", 1);
        var dto = new CreateLessonDto("New", "Desc", 1, 1, "Topic");
        var lesson = Lesson.Create(1, "New", 1, "Topic", "Desc");
        
        _mockLevelRepo.Setup(r => r.GetByIdAsync(1, It.IsAny<CancellationToken>()))
            .ReturnsAsync(level);
        _mockLessonRepo.Setup(r => r.AddAsync(It.IsAny<Lesson>(), It.IsAny<CancellationToken>()))
            .ReturnsAsync(lesson);

        var result = await _service.CreateLessonAsync(dto);

        Assert.IsNotNull(result);
        Assert.AreEqual("New", result.Title);
    }

    [TestMethod]
    public async Task UpdateLessonAsync_WithExistingLesson_UpdatesLesson()
    {
        var existing = Lesson.Create(1, "Old", 1, "OldT", "OldD");
        var level = Level.Create("A1", "A1", 1);
        var dto = new UpdateLessonDto("New", "NewD", 1, 1, "NewT");
        
        _mockLessonRepo.Setup(r => r.GetByIdAsync(1, It.IsAny<CancellationToken>()))
            .ReturnsAsync(existing);
        _mockLevelRepo.Setup(r => r.GetByIdAsync(1, It.IsAny<CancellationToken>()))
            .ReturnsAsync(level);
        _mockLessonRepo.Setup(r => r.UpdateAsync(existing, It.IsAny<CancellationToken>()))
            .Returns(Task.CompletedTask);

        var result = await _service.UpdateLessonAsync(1, dto);

        Assert.IsNotNull(result);
    }

    [TestMethod]
    public async Task DeleteLessonAsync_WithExistingLesson_ReturnsTrue()
    {
        var lesson = Lesson.Create(1, "Test", 1, "Topic", "Desc");
        _mockLessonRepo.Setup(r => r.GetByIdAsync(1, It.IsAny<CancellationToken>()))
            .ReturnsAsync(lesson);
        _mockLessonRepo.Setup(r => r.DeleteAsync(lesson, It.IsAny<CancellationToken>()))
            .Returns(Task.CompletedTask);

        var result = await _service.DeleteLessonAsync(1);

        Assert.IsTrue(result);
    }

    [TestMethod]
    public async Task GetBeginnerLessonsAsync_ReturnsA1AndA2Lessons()
    {
        var level1 = new List<Lesson> { Lesson.Create(1, "A1L1", 1, "T1", "D1") };
        var level2 = new List<Lesson> { Lesson.Create(2, "A2L1", 1, "T2", "D2") };
        
        _mockLessonRepo.Setup(r => r.GetByLevelAsync(1, It.IsAny<CancellationToken>()))
            .ReturnsAsync(level1);
        _mockLessonRepo.Setup(r => r.GetByLevelAsync(2, It.IsAny<CancellationToken>()))
            .ReturnsAsync(level2);

        var result = await _service.GetBeginnerLessonsAsync();

        Assert.AreEqual(2, result.Count);
    }

    [TestMethod]
    public async Task GetAdvancedLessonsAsync_ReturnsB2AndC1Lessons()
    {
        var level4 = new List<Lesson> { Lesson.Create(4, "B2L1", 1, "T4", "D4") };
        var level5 = new List<Lesson> { Lesson.Create(5, "C1L1", 1, "T5", "D5") };
        
        _mockLessonRepo.Setup(r => r.GetByLevelAsync(4, It.IsAny<CancellationToken>()))
            .ReturnsAsync(level4);
        _mockLessonRepo.Setup(r => r.GetByLevelAsync(5, It.IsAny<CancellationToken>()))
            .ReturnsAsync(level5);

        var result = await _service.GetAdvancedLessonsAsync();

        Assert.AreEqual(2, result.Count);
    }
}