Fix blog service tests and admin empty states

src/TaxBaik.Application.Tests/BlogServiceTests.cs

@@ -13,7 +13,11 @@ public class BlogServiceTests
     [Fact]
     public async Task CreateAsync_WhenPublishedWithoutSeoTitle_ThrowsValidationException()
     {
-        var service = new BlogService(new FakeBlogPostRepository(), new MemoryCache(new MemoryCacheOptions()), new PassThroughValidator<CreateBlogPostDto>());
+        var service = new BlogService(
+            new FakeBlogPostRepository(),
+            new FakeCategoryRepository(),
+            new MemoryCache(new MemoryCacheOptions()),
+            new PassThroughValidator<CreateBlogPostDto>());
 
         await Assert.ThrowsAsync<TaxBaik.Application.Services.ValidationException>(() => service.CreateAsync(new CreateBlogPostDto
         {
@@ -34,7 +38,11 @@ public class BlogServiceTests
                 new BlogPost { Id = 1, Title = "같은 제목", Content = "본문", Slug = "같은-제목" }
             ]
         };
-        var service = new BlogService(repository, new MemoryCache(new MemoryCacheOptions()), new PassThroughValidator<CreateBlogPostDto>());
+        var service = new BlogService(
+            repository,
+            new FakeCategoryRepository(),
+            new MemoryCache(new MemoryCacheOptions()),
+            new PassThroughValidator<CreateBlogPostDto>());
 
         var post = await service.CreateAsync(new CreateBlogPostDto
         {
@@ -55,7 +63,11 @@ public class BlogServiceTests
                 new BlogPost { Id = 1, Title = "삭제 대상", Content = "본문", Slug = "delete-me", IsPublished = true }
             ]
         };
-        var service = new BlogService(repository, new MemoryCache(new MemoryCacheOptions()), new PassThroughValidator<CreateBlogPostDto>());
+        var service = new BlogService(
+            repository,
+            new FakeCategoryRepository(),
+            new MemoryCache(new MemoryCacheOptions()),
+            new PassThroughValidator<CreateBlogPostDto>());
 
         await service.DeleteAsync(1);
 
@@ -131,6 +143,34 @@ public class BlogServiceTests
         public Task IncrementViewCountAsync(int id, CancellationToken cancellationToken = default) => Task.CompletedTask;
     }
 
+    private sealed class FakeCategoryRepository : ICategoryRepository
+    {
+        private readonly List<Category> _categories =
+        [
+            new Category { Id = 1, Name = "사업자 세무", Slug = "business-tax", SortOrder = 1 }
+        ];
+
+        public Task<IEnumerable<Category>> GetAllAsync(CancellationToken cancellationToken = default) =>
+            Task.FromResult<IEnumerable<Category>>(_categories);
+
+        public Task<Category?> GetBySlugAsync(string slug, CancellationToken cancellationToken = default) =>
+            Task.FromResult(_categories.FirstOrDefault(x => x.Slug == slug));
+
+        public Task<Category?> GetByIdAsync(int id, CancellationToken cancellationToken = default) =>
+            Task.FromResult(_categories.FirstOrDefault(x => x.Id == id));
+
+        public Task<int> CreateAsync(Category category, CancellationToken cancellationToken = default)
+        {
+            category.Id = _categories.Count + 1;
+            _categories.Add(category);
+            return Task.FromResult(category.Id);
+        }
+
+        public Task UpdateAsync(Category category, CancellationToken cancellationToken = default) => Task.CompletedTask;
+
+        public Task DeleteAsync(int id, CancellationToken cancellationToken = default) => Task.CompletedTask;
+    }
+
     private sealed class PassThroughValidator<T> : IValidator<T>
     {
         public FluentValidation.Results.ValidationResult Validate(T instance) => new();