diff --git a/app/infrastructure/middleware/error_handler.py b/app/infrastructure/middleware/error_handler.py
index 88f11ce..247b24a 100644
--- a/app/infrastructure/middleware/error_handler.py
+++ b/app/infrastructure/middleware/error_handler.py
@@ -129,3 +129,4 @@ def register_exception_handlers(app: FastAPI) -> None:
 
     app.add_exception_handler(DomainException, domain_exception_handler)  # type: ignore[arg-type]
     app.add_exception_handler(StarletteHTTPException, http_exception_handler)  # type: ignore[arg-type]
+    app.add_exception_handler(Exception, generic_exception_handler)
diff --git a/tests/api/test_error_handlers.py b/tests/api/test_error_handlers.py
new file mode 100644
index 0000000..7156223
--- /dev/null
+++ b/tests/api/test_error_handlers.py
@@ -0,0 +1,207 @@
+"""Tests for error handler middleware.
+
+Tests exception handling and error responses.
+"""
+
+from unittest.mock import patch
+
+from httpx import ASGITransport, AsyncClient
+
+from app.domain.exceptions import (
+    AlreadyExistsException,
+    DomainException,
+    ForbiddenException,
+    NotFoundException,
+    ValidationException,
+)
+from app.main import app_factory
+
+
+class TestDomainExceptionHandlers:
+    """Test suite for domain exception handlers."""
+
+    async def test_validation_exception(self) -> None:
+        """Test ValidationException returns 400."""
+        with patch(
+            "app.application.use_cases.get_post.GetPostUseCase.by_id",
+            side_effect=ValidationException("Invalid input"),
+        ):
+            app = app_factory()
+            transport = ASGITransport(app=app)
+            async with AsyncClient(transport=transport, base_url="http://test") as client:
+                response = await client.get("/api/v1/posts/12345678-1234-1234-1234-123456789abc")
+
+                assert response.status_code == 400
+                data = response.json()
+                assert data["error"] == "ValidationException"
+                assert data["message"] == "Invalid input"
+                assert "timestamp" in data
+                assert "path" in data
+
+    async def test_forbidden_exception(self) -> None:
+        """Test ForbiddenException returns 403."""
+        with patch(
+            "app.application.use_cases.get_post.GetPostUseCase.by_id",
+            side_effect=ForbiddenException("Access denied"),
+        ):
+            app = app_factory()
+            transport = ASGITransport(app=app)
+            async with AsyncClient(transport=transport, base_url="http://test") as client:
+                response = await client.get("/api/v1/posts/12345678-1234-1234-1234-123456789abc")
+
+                assert response.status_code == 403
+                data = response.json()
+                assert data["error"] == "ForbiddenException"
+                assert data["message"] == "Access denied"
+
+    async def test_not_found_exception(self) -> None:
+        """Test NotFoundException returns 404."""
+        with patch(
+            "app.application.use_cases.get_post.GetPostUseCase.by_id",
+            side_effect=NotFoundException("Post not found"),
+        ):
+            app = app_factory()
+            transport = ASGITransport(app=app)
+            async with AsyncClient(transport=transport, base_url="http://test") as client:
+                response = await client.get("/api/v1/posts/12345678-1234-1234-1234-123456789abc")
+
+                assert response.status_code == 404
+                data = response.json()
+                assert data["error"] == "NotFoundException"
+                assert data["message"] == "Post not found"
+
+    async def test_already_exists_exception(self) -> None:
+        """Test AlreadyExistsException returns 409."""
+        with patch(
+            "app.application.use_cases.get_post.GetPostUseCase.by_id",
+            side_effect=AlreadyExistsException("Post already exists"),
+        ):
+            app = app_factory()
+            transport = ASGITransport(app=app)
+            async with AsyncClient(transport=transport, base_url="http://test") as client:
+                response = await client.get("/api/v1/posts/12345678-1234-1234-1234-123456789abc")
+
+                assert response.status_code == 409
+                data = response.json()
+                assert data["error"] == "AlreadyExistsException"
+                assert data["message"] == "Post already exists"
+
+    async def test_generic_domain_exception(self) -> None:
+        """Test generic DomainException returns 500."""
+        with patch(
+            "app.application.use_cases.get_post.GetPostUseCase.by_id",
+            side_effect=DomainException("Generic error"),
+        ):
+            app = app_factory()
+            transport = ASGITransport(app=app)
+            async with AsyncClient(transport=transport, base_url="http://test") as client:
+                response = await client.get("/api/v1/posts/12345678-1234-1234-1234-123456789abc")
+
+                assert response.status_code == 500
+                data = response.json()
+                assert data["error"] == "DomainException"
+                assert data["message"] == "Generic error"
+
+
+class TestHTTPExceptionHandler:
+    """Test suite for HTTP exception handling."""
+
+    async def test_http_exception_structure(self) -> None:
+        """Test HTTP exception response structure."""
+        # Test that exception handler is registered and produces correct format
+        import json
+        from dataclasses import dataclass, field
+
+        from starlette.exceptions import HTTPException
+
+        from app.infrastructure.middleware.error_handler import http_exception_handler
+
+        # Create mock request
+        @dataclass
+        class MockURL:
+            path: str = "/test"
+
+        @dataclass
+        class MockRequest:
+            url: MockURL = field(default_factory=MockURL)
+
+        exc = HTTPException(status_code=404, detail="Not found")
+        response = await http_exception_handler(MockRequest(), exc)  # type: ignore[arg-type]
+
+        assert response.status_code == 404
+        body_bytes: bytes = response.body  # type: ignore[assignment]
+        data: dict[str, object] = json.loads(body_bytes.decode("utf-8"))
+        assert data["error"] == "HTTPException"
+        assert "message" in data
+
+
+class TestGenericExceptionHandler:
+    """Test suite for generic exception handling."""
+
+    async def test_generic_exception_handler_function(self) -> None:
+        """Test generic exception handler function directly."""
+        import json
+        from dataclasses import dataclass, field
+
+        from app.infrastructure.middleware.error_handler import (
+            generic_exception_handler,
+        )
+
+        # Create mock request
+        @dataclass
+        class MockURL:
+            path: str = "/test"
+
+        @dataclass
+        class MockRequest:
+            url: MockURL = field(default_factory=MockURL)
+
+        exc = RuntimeError("Internal error")
+        response = await generic_exception_handler(MockRequest(), exc)  # type: ignore[arg-type]
+
+        assert response.status_code == 500
+        body_bytes: bytes = response.body  # type: ignore[assignment]
+        data: dict[str, object] = json.loads(body_bytes.decode("utf-8"))
+        assert data["error"] == "InternalServerError"
+        assert data["message"] == "An unexpected error occurred"
+        assert "timestamp" in data
+        assert "path" in data
+
+
+class TestGetStatusCode:
+    """Test suite for get_status_code function."""
+
+    def test_validation_exception_status(self) -> None:
+        """Test ValidationException maps to 400."""
+        from app.infrastructure.middleware.error_handler import get_status_code
+
+        exc = ValidationException("Invalid")
+        assert get_status_code(exc) == 400
+
+    def test_forbidden_exception_status(self) -> None:
+        """Test ForbiddenException maps to 403."""
+        from app.infrastructure.middleware.error_handler import get_status_code
+
+        exc = ForbiddenException("Forbidden")
+        assert get_status_code(exc) == 403
+
+    def test_not_found_exception_status(self) -> None:
+        """Test NotFoundException maps to 404."""
+        from app.infrastructure.middleware.error_handler import get_status_code
+
+        exc = NotFoundException("Not found")
+        assert get_status_code(exc) == 404
+
+    def test_already_exists_exception_status(self) -> None:
+        """Test AlreadyExistsException maps to 409."""
+        from app.infrastructure.middleware.error_handler import get_status_code
+
+        exc = AlreadyExistsException("Already exists")
+        assert get_status_code(exc) == 409
+
+    def test_generic_exception_status(self) -> None:
+        """Test generic DomainException maps to 500."""
+        from app.infrastructure.middleware.error_handler import get_status_code
+
+        exc = DomainException("Generic")
+        assert get_status_code(exc) == 500
diff --git a/tests/api/test_posts.py b/tests/api/test_posts.py
new file mode 100644
index 0000000..da4c13e
--- /dev/null
+++ b/tests/api/test_posts.py
@@ -0,0 +1,318 @@
+"""API tests for posts endpoints.
+
+Tests REST API endpoints - focusing on endpoints that don't require
+complex Dishka dependency mocking.
+"""
+
+from datetime import datetime
+from unittest.mock import patch
+from uuid import uuid4
+
+import pytest
+from httpx import ASGITransport, AsyncClient
+
+from app.application.dtos import PostResponseDTO
+from app.domain.exceptions import NotFoundException
+from app.main import app_factory
+
+
+@pytest.fixture
+def sample_post_dto() -> PostResponseDTO:
+    """Create a sample post DTO for testing."""
+    return PostResponseDTO(
+        id=uuid4(),
+        title="Test Post",
+        content="This is test content for the blog post",
+        slug="test-post",
+        author_id="test-user-id",
+        published=True,
+        tags=["python", "testing"],
+        created_at=datetime.now(),
+        updated_at=datetime.now(),
+    )
+
+
+class TestListPublishedPosts:
+    """Test suite for GET /api/v1/posts/published endpoint."""
+
+    async def test_list_published_posts(
+        self,
+        sample_post_dto: PostResponseDTO,
+    ) -> None:
+        """Test listing published posts without authentication."""
+        with patch(
+            "app.application.use_cases.list_posts.ListPostsUseCase.published_posts",
+            return_value=[sample_post_dto],
+        ):
+            app = app_factory()
+            transport = ASGITransport(app=app)
+            async with AsyncClient(transport=transport, base_url="http://test") as client:
+                response = await client.get("/api/v1/posts/published")
+
+                assert response.status_code == 200
+                data = response.json()
+                assert "items" in data
+                assert data["total"] == 1
+
+
+class TestSearchPosts:
+    """Test suite for GET /api/v1/posts/search endpoint."""
+
+    async def test_search_posts(
+        self,
+        sample_post_dto: PostResponseDTO,
+    ) -> None:
+        """Test searching posts by query."""
+        with patch(
+            "app.application.use_cases.list_posts.ListPostsUseCase.search",
+            return_value=[sample_post_dto],
+        ):
+            app = app_factory()
+            transport = ASGITransport(app=app)
+            async with AsyncClient(transport=transport, base_url="http://test") as client:
+                response = await client.get("/api/v1/posts/search?query=test")
+
+                assert response.status_code == 200
+                data = response.json()
+                assert "items" in data
+                assert data["total"] == 1
+
+    async def test_search_posts_empty_query(self) -> None:
+        """Test search with empty query returns empty results."""
+        with patch(
+            "app.application.use_cases.list_posts.ListPostsUseCase.search",
+            return_value=[],
+        ):
+            app = app_factory()
+            transport = ASGITransport(app=app)
+            async with AsyncClient(transport=transport, base_url="http://test") as client:
+                response = await client.get("/api/v1/posts/search?query=")
+
+                # Empty query returns 200 with empty results (not 422)
+                # as query param accepts empty strings
+                assert response.status_code == 200
+                data = response.json()
+                assert data["items"] == []
+                assert data["total"] == 0
+
+
+class TestGetPostsByTag:
+    """Test suite for GET /api/v1/posts/by-tag/{tag} endpoint."""
+
+    async def test_get_posts_by_tag(
+        self,
+        sample_post_dto: PostResponseDTO,
+    ) -> None:
+        """Test getting posts by tag."""
+        with patch(
+            "app.application.use_cases.list_posts.ListPostsUseCase.by_tag",
+            return_value=[sample_post_dto],
+        ):
+            app = app_factory()
+            transport = ASGITransport(app=app)
+            async with AsyncClient(transport=transport, base_url="http://test") as client:
+                response = await client.get("/api/v1/posts/by-tag/python")
+
+                assert response.status_code == 200
+                data = response.json()
+                assert "items" in data
+                assert data["total"] == 1
+
+
+class TestGetPostsByAuthor:
+    """Test suite for GET /api/v1/posts/by-author/{author_id} endpoint."""
+
+    async def test_get_posts_by_author(
+        self,
+        sample_post_dto: PostResponseDTO,
+    ) -> None:
+        """Test getting posts by author."""
+        with patch(
+            "app.application.use_cases.list_posts.ListPostsUseCase.by_author",
+            return_value=[sample_post_dto],
+        ):
+            app = app_factory()
+            transport = ASGITransport(app=app)
+            async with AsyncClient(transport=transport, base_url="http://test") as client:
+                response = await client.get("/api/v1/posts/by-author/test-user-id")
+
+                assert response.status_code == 200
+                data = response.json()
+                assert "items" in data
+                assert data["total"] == 1
+
+
+class TestGetPostById:
+    """Test suite for GET /api/v1/posts/{post_id} endpoint."""
+
+    async def test_get_post_by_id_success(
+        self,
+        sample_post_dto: PostResponseDTO,
+    ) -> None:
+        """Test getting a post by ID."""
+        with patch(
+            "app.application.use_cases.get_post.GetPostUseCase.by_id",
+            return_value=sample_post_dto,
+        ):
+            app = app_factory()
+            transport = ASGITransport(app=app)
+            async with AsyncClient(transport=transport, base_url="http://test") as client:
+                response = await client.get(f"/api/v1/posts/{sample_post_dto.id}")
+
+                assert response.status_code == 200
+                data = response.json()
+                assert data["id"] == str(sample_post_dto.id)
+                assert data["title"] == sample_post_dto.title
+
+    async def test_get_post_by_id_not_found(self) -> None:
+        """Test getting a non-existing post returns 404."""
+        with patch(
+            "app.application.use_cases.get_post.GetPostUseCase.by_id",
+            side_effect=NotFoundException("Post not found"),
+        ):
+            app = app_factory()
+            transport = ASGITransport(app=app)
+            async with AsyncClient(transport=transport, base_url="http://test") as client:
+                response = await client.get(f"/api/v1/posts/{uuid4()}")
+
+                assert response.status_code == 404
+
+
+class TestGetPostBySlug:
+    """Test suite for GET /api/v1/posts/slug/{slug} endpoint."""
+
+    async def test_get_post_by_slug_success(
+        self,
+        sample_post_dto: PostResponseDTO,
+    ) -> None:
+        """Test getting a post by slug."""
+        with patch(
+            "app.application.use_cases.get_post.GetPostUseCase.by_slug",
+            return_value=sample_post_dto,
+        ):
+            app = app_factory()
+            transport = ASGITransport(app=app)
+            async with AsyncClient(transport=transport, base_url="http://test") as client:
+                response = await client.get("/api/v1/posts/slug/test-post")
+
+                assert response.status_code == 200
+                data = response.json()
+                assert data["slug"] == "test-post"
+
+    async def test_get_post_by_slug_not_found(self) -> None:
+        """Test getting a non-existing post by slug returns 404."""
+        with patch(
+            "app.application.use_cases.get_post.GetPostUseCase.by_slug",
+            side_effect=NotFoundException("Post not found"),
+        ):
+            app = app_factory()
+            transport = ASGITransport(app=app)
+            async with AsyncClient(transport=transport, base_url="http://test") as client:
+                response = await client.get("/api/v1/posts/slug/non-existing-slug")
+
+                assert response.status_code == 404
+
+
+class TestCreatePostAuth:
+    """Test suite for POST /api/v1/posts authentication."""
+
+    async def test_create_post_unauthorized(self) -> None:
+        """Test post creation without authentication returns 401."""
+        app = app_factory()
+        transport = ASGITransport(app=app)
+        async with AsyncClient(transport=transport, base_url="http://test") as client:
+            response = await client.post(
+                "/api/v1/posts",
+                json={
+                    "title": "Test Post",
+                    "content": "This is test content for the blog post",
+                },
+            )
+
+            assert response.status_code == 401
+
+
+class TestUpdatePostAuth:
+    """Test suite for PATCH /api/v1/posts/{post_id} authentication."""
+
+    async def test_update_post_unauthorized(self) -> None:
+        """Test updating post without authentication returns 401."""
+        app = app_factory()
+        transport = ASGITransport(app=app)
+        async with AsyncClient(transport=transport, base_url="http://test") as client:
+            response = await client.patch(
+                f"/api/v1/posts/{uuid4()}",
+                json={"title": "Updated Title"},
+            )
+
+            assert response.status_code == 401
+
+
+class TestDeletePostAuth:
+    """Test suite for DELETE /api/v1/posts/{post_id} authentication."""
+
+    async def test_delete_post_unauthorized(self) -> None:
+        """Test deleting post without authentication returns 401."""
+        app = app_factory()
+        transport = ASGITransport(app=app)
+        async with AsyncClient(transport=transport, base_url="http://test") as client:
+            response = await client.delete(f"/api/v1/posts/{uuid4()}")
+
+            assert response.status_code == 401
+
+
+class TestPublishPostAuth:
+    """Test suite for POST /api/v1/posts/{post_id}/publish authentication."""
+
+    async def test_publish_post_unauthorized(self) -> None:
+        """Test publishing post without authentication returns 401."""
+        app = app_factory()
+        transport = ASGITransport(app=app)
+        async with AsyncClient(transport=transport, base_url="http://test") as client:
+            response = await client.post(f"/api/v1/posts/{uuid4()}/publish")
+
+            assert response.status_code == 401
+
+
+class TestUnpublishPostAuth:
+    """Test suite for POST /api/v1/posts/{post_id}/unpublish authentication."""
+
+    async def test_unpublish_post_unauthorized(self) -> None:
+        """Test unpublishing post without authentication returns 401."""
+        app = app_factory()
+        transport = ASGITransport(app=app)
+        async with AsyncClient(transport=transport, base_url="http://test") as client:
+            response = await client.post(f"/api/v1/posts/{uuid4()}/unpublish")
+
+            assert response.status_code == 401
+
+
+class TestHealthEndpoint:
+    """Test suite for health check endpoint."""
+
+    async def test_health_check(self) -> None:
+        """Test health check endpoint returns ok status."""
+        app = app_factory()
+        transport = ASGITransport(app=app)
+        async with AsyncClient(transport=transport, base_url="http://test") as client:
+            response = await client.get("/health")
+
+            assert response.status_code == 200
+            data = response.json()
+            assert data["status"] == "ok"
+            assert "app" in data
+            assert "env" in data
+
+
+class TestRootRedirect:
+    """Test suite for root redirect."""
+
+    async def test_root_redirect(self) -> None:
+        """Test root URL redirects to web UI."""
+        app = app_factory()
+        transport = ASGITransport(app=app)
+        async with AsyncClient(transport=transport, base_url="http://test") as client:
+            response = await client.get("/")
+
+            assert response.status_code == 200
+            assert "web/" in response.text
diff --git a/tests/integration/test_repositories.py b/tests/integration/test_repositories.py
new file mode 100644
index 0000000..1fbc49b
--- /dev/null
+++ b/tests/integration/test_repositories.py
@@ -0,0 +1,479 @@
+"""Integration tests for SQLAlchemyPostRepository.
+
+Tests repository implementation with real in-memory SQLite database.
+Note: Some tests involving JSON array operations are skipped for SQLite
+as it has limited support compared to PostgreSQL.
+"""
+
+from uuid import UUID, uuid4
+
+import pytest
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.domain.entities import Post
+from app.domain.repositories import PostRepository
+from app.domain.value_objects import Content, Slug, Title
+from app.infrastructure.repositories.post import SQLAlchemyPostRepository
+
+
+@pytest.fixture
+def repository(db_session: AsyncSession) -> PostRepository:
+    """Create repository instance for testing."""
+    return SQLAlchemyPostRepository(db_session)
+
+
+@pytest.fixture
+def sample_post() -> Post:
+    """Create a sample post for testing."""
+    return Post(
+        id=uuid4(),
+        title=Title("Test Post Title"),
+        content=Content("Test content for the blog post"),
+        slug=Slug("test-post-title"),
+        author_id="test-author-123",
+        published=False,
+        tags=["python", "testing"],
+    )
+
+
+@pytest.fixture
+def published_post() -> Post:
+    """Create a published post for testing."""
+    post = Post(
+        id=uuid4(),
+        title=Title("Published Post"),
+        content=Content("This is a published post content"),
+        slug=Slug("published-post"),
+        author_id="test-author-456",
+        published=True,
+        tags=["published", "blog"],
+    )
+    return post
+
+
+class TestPostRepositoryCreate:
+    """Test suite for post creation operations."""
+
+    async def test_add_post(
+        self,
+        repository: PostRepository,
+        sample_post: Post,
+        db_session: AsyncSession,
+    ) -> None:
+        """Test adding a new post to the database."""
+        await repository.add(sample_post)
+        await db_session.commit()
+
+        retrieved = await repository.get_by_id(sample_post.id)
+
+        assert retrieved is not None
+        assert retrieved.id == sample_post.id
+        assert retrieved.title.value == sample_post.title.value
+        assert retrieved.content.value == sample_post.content.value
+        assert retrieved.slug.value == sample_post.slug.value
+        assert retrieved.author_id == sample_post.author_id
+        assert retrieved.published == sample_post.published
+        assert retrieved.tags == sample_post.tags
+
+    async def test_get_by_id_existing(
+        self,
+        repository: PostRepository,
+        sample_post: Post,
+        db_session: AsyncSession,
+    ) -> None:
+        """Test retrieving an existing post by ID."""
+        await repository.add(sample_post)
+        await db_session.commit()
+
+        result = await repository.get_by_id(sample_post.id)
+
+        assert result is not None
+        assert result.id == sample_post.id
+
+    async def test_get_by_id_non_existing(self, repository: PostRepository) -> None:
+        """Test retrieving a non-existing post returns None."""
+        non_existing_id = uuid4()
+
+        result = await repository.get_by_id(non_existing_id)
+
+        assert result is None
+
+
+class TestPostRepositoryGetAll:
+    """Test suite for retrieving all posts."""
+
+    async def test_get_all_empty(self, repository: PostRepository) -> None:
+        """Test retrieving all posts when database is empty."""
+        results = await repository.get_all()
+
+        assert results == []
+
+    async def test_get_all_multiple_posts(
+        self,
+        repository: PostRepository,
+        sample_post: Post,
+        published_post: Post,
+        db_session: AsyncSession,
+    ) -> None:
+        """Test retrieving all posts returns all entries."""
+        await repository.add(sample_post)
+        await repository.add(published_post)
+        await db_session.commit()
+
+        results = await repository.get_all()
+
+        assert len(results) == 2
+        ids = {post.id for post in results}
+        assert sample_post.id in ids
+        assert published_post.id in ids
+
+
+class TestPostRepositoryUpdate:
+    """Test suite for post update operations."""
+
+    async def test_update_post(
+        self,
+        repository: PostRepository,
+        sample_post: Post,
+        db_session: AsyncSession,
+    ) -> None:
+        """Test updating an existing post."""
+        await repository.add(sample_post)
+        await db_session.commit()
+
+        # Refresh to get latest state
+        await db_session.flush()
+
+        # Create a new post instance with updated values
+        updated_post = Post(
+            id=sample_post.id,
+            title=Title("Updated Title"),
+            content=Content("Updated content for the post"),
+            slug=sample_post.slug,
+            author_id=sample_post.author_id,
+            published=sample_post.published,
+            tags=["updated", "tags"],
+            created_at=sample_post.created_at,
+            updated_at=sample_post.updated_at,
+        )
+
+        await repository.update(updated_post)
+        await db_session.commit()
+
+        retrieved = await repository.get_by_id(sample_post.id)
+
+        assert retrieved is not None
+        assert retrieved.title.value == "Updated Title"
+        assert retrieved.content.value == "Updated content for the post"
+        assert retrieved.tags == ["updated", "tags"]
+
+    async def test_update_publishes_post(
+        self,
+        repository: PostRepository,
+        sample_post: Post,
+        db_session: AsyncSession,
+    ) -> None:
+        """Test that update reflects published status change."""
+        await repository.add(sample_post)
+        await db_session.commit()
+        await db_session.flush()
+
+        # Create updated post with published=True
+        updated_post = Post(
+            id=sample_post.id,
+            title=sample_post.title,
+            content=sample_post.content,
+            slug=sample_post.slug,
+            author_id=sample_post.author_id,
+            published=True,
+            tags=sample_post.tags,
+            created_at=sample_post.created_at,
+            updated_at=sample_post.updated_at,
+        )
+
+        await repository.update(updated_post)
+        await db_session.commit()
+
+        retrieved = await repository.get_by_id(sample_post.id)
+
+        assert retrieved is not None
+        assert retrieved.published is True
+
+
+class TestPostRepositoryDelete:
+    """Test suite for post deletion operations."""
+
+    async def test_delete_existing_post(
+        self,
+        repository: PostRepository,
+        sample_post: Post,
+        db_session: AsyncSession,
+    ) -> None:
+        """Test deleting an existing post."""
+        await repository.add(sample_post)
+        await db_session.commit()
+
+        await repository.delete(sample_post.id)
+        await db_session.commit()
+
+        retrieved = await repository.get_by_id(sample_post.id)
+        assert retrieved is None
+
+    async def test_delete_non_existing_post(self, repository: PostRepository) -> None:
+        """Test deleting a non-existing post does not raise error."""
+        non_existing_id = uuid4()
+
+        await repository.delete(non_existing_id)
+
+
+class TestPostRepositoryExists:
+    """Test suite for post existence checks."""
+
+    async def test_exists_true(
+        self,
+        repository: PostRepository,
+        sample_post: Post,
+        db_session: AsyncSession,
+    ) -> None:
+        """Test exists returns True for existing post."""
+        await repository.add(sample_post)
+        await db_session.commit()
+
+        result = await repository.exists(sample_post.id)
+
+        assert result is True
+
+    async def test_exists_false(self, repository: PostRepository) -> None:
+        """Test exists returns False for non-existing post."""
+        non_existing_id = uuid4()
+
+        result = await repository.exists(non_existing_id)
+
+        assert result is False
+
+
+class TestPostRepositoryGetBySlug:
+    """Test suite for slug-based retrieval."""
+
+    async def test_get_by_slug_existing(
+        self,
+        repository: PostRepository,
+        sample_post: Post,
+        db_session: AsyncSession,
+    ) -> None:
+        """Test retrieving post by existing slug."""
+        await repository.add(sample_post)
+        await db_session.commit()
+
+        result = await repository.get_by_slug(sample_post.slug.value)
+
+        assert result is not None
+        assert result.id == sample_post.id
+        assert result.slug.value == sample_post.slug.value
+
+    async def test_get_by_slug_non_existing(self, repository: PostRepository) -> None:
+        """Test retrieving by non-existing slug returns None."""
+        result = await repository.get_by_slug("non-existing-slug")
+
+        assert result is None
+
+
+class TestPostRepositoryGetByAuthor:
+    """Test suite for author-based retrieval."""
+
+    async def test_get_by_author(
+        self,
+        repository: PostRepository,
+        sample_post: Post,
+        db_session: AsyncSession,
+    ) -> None:
+        """Test retrieving posts by author ID."""
+        await repository.add(sample_post)
+        await db_session.commit()
+
+        results = await repository.get_by_author(sample_post.author_id)
+
+        assert len(results) == 1
+        assert results[0].id == sample_post.id
+
+    async def test_get_by_author_empty(self, repository: PostRepository) -> None:
+        """Test retrieving posts by author with no posts."""
+        results = await repository.get_by_author("non-existing-author")
+
+        assert results == []
+
+
+class TestPostRepositoryGetPublished:
+    """Test suite for published posts retrieval."""
+
+    async def test_get_published_only(
+        self,
+        repository: PostRepository,
+        sample_post: Post,
+        published_post: Post,
+        db_session: AsyncSession,
+    ) -> None:
+        """Test retrieving only published posts."""
+        await repository.add(sample_post)
+        await repository.add(published_post)
+        await db_session.commit()
+
+        results = await repository.get_published()
+
+        assert len(results) == 1
+        assert results[0].id == published_post.id
+
+
+class TestPostRepositoryGetByTag:
+    """Test suite for tag-based retrieval.
+
+    Note: These tests are skipped for SQLite as it has limited JSON support.
+    """
+
+    @pytest.mark.skip(reason="SQLite has limited JSON array support")
+    async def test_get_by_tag(self, repository: PostRepository, sample_post: Post) -> None:
+        """Test retrieving posts by tag."""
+        pass
+
+    @pytest.mark.skip(reason="SQLite has limited JSON array support")
+    async def test_get_by_tag_multiple_posts(self, repository: PostRepository) -> None:
+        """Test retrieving multiple posts with same tag."""
+        pass
+
+    @pytest.mark.skip(reason="SQLite has limited JSON array support")
+    async def test_get_by_tag_not_found(
+        self,
+        repository: PostRepository,
+        sample_post: Post,
+    ) -> None:
+        """Test retrieving by non-existing tag returns empty list."""
+        pass
+
+
+class TestPostRepositorySlugExists:
+    """Test suite for slug existence checks."""
+
+    async def test_slug_exists_true(
+        self,
+        repository: PostRepository,
+        sample_post: Post,
+        db_session: AsyncSession,
+    ) -> None:
+        """Test slug_exists returns True for existing slug."""
+        await repository.add(sample_post)
+        await db_session.commit()
+
+        result = await repository.slug_exists(sample_post.slug.value)
+
+        assert result is True
+
+    async def test_slug_exists_false(self, repository: PostRepository) -> None:
+        """Test slug_exists returns False for non-existing slug."""
+        result = await repository.slug_exists("non-existing-slug")
+
+        assert result is False
+
+
+class TestPostRepositorySearch:
+    """Test suite for post search functionality."""
+
+    async def test_search_by_title(
+        self,
+        repository: PostRepository,
+        sample_post: Post,
+        db_session: AsyncSession,
+    ) -> None:
+        """Test searching posts by title."""
+        await repository.add(sample_post)
+        await db_session.commit()
+
+        results = await repository.search("Test Post")
+
+        assert len(results) == 1
+        assert results[0].id == sample_post.id
+
+    async def test_search_by_content(
+        self,
+        repository: PostRepository,
+        sample_post: Post,
+        db_session: AsyncSession,
+    ) -> None:
+        """Test searching posts by content."""
+        await repository.add(sample_post)
+        await db_session.commit()
+
+        results = await repository.search("blog post")
+
+        assert len(results) == 1
+        assert results[0].id == sample_post.id
+
+    async def test_search_case_insensitive(
+        self,
+        repository: PostRepository,
+        sample_post: Post,
+        db_session: AsyncSession,
+    ) -> None:
+        """Test search is case insensitive."""
+        await repository.add(sample_post)
+        await db_session.commit()
+
+        results = await repository.search("TEST POST")
+
+        assert len(results) == 1
+
+    async def test_search_no_results(
+        self,
+        repository: PostRepository,
+        sample_post: Post,
+        db_session: AsyncSession,
+    ) -> None:
+        """Test search with no matching results."""
+        await repository.add(sample_post)
+        await db_session.commit()
+
+        results = await repository.search("xyz123nonexistent")
+
+        assert results == []
+
+    @pytest.mark.skip(reason="SQLite behavior without ORDER BY is non-deterministic")
+    async def test_search_with_limit(
+        self,
+        repository: PostRepository,
+        db_session: AsyncSession,
+    ) -> None:
+        """Test search with limit - skipped for SQLite."""
+        pass
+
+    @pytest.mark.skip(reason="SQLite order non-deterministic without ORDER BY")
+    async def test_search_with_offset(
+        self,
+        repository: PostRepository,
+        db_session: AsyncSession,
+    ) -> None:
+        """Test search with offset."""
+        pass
+
+
+class TestPostRepositoryConversion:
+    """Test suite for domain/ORM conversion."""
+
+    async def test_to_domain_preserves_all_fields(
+        self,
+        repository: SQLAlchemyPostRepository,
+        sample_post: Post,
+        db_session: AsyncSession,
+    ) -> None:
+        """Test that domain conversion preserves all post fields."""
+        await repository.add(sample_post)
+        await db_session.commit()
+
+        retrieved = await repository.get_by_id(sample_post.id)
+
+        assert retrieved is not None
+        assert isinstance(retrieved.id, UUID)
+        assert retrieved.title.value == sample_post.title.value
+        assert retrieved.content.value == sample_post.content.value
+        assert retrieved.slug.value == sample_post.slug.value
+        assert retrieved.author_id == sample_post.author_id
+        assert retrieved.published == sample_post.published
+        assert retrieved.tags == sample_post.tags
diff --git a/tests/unit/application/test_list_posts.py b/tests/unit/application/test_list_posts.py
new file mode 100644
index 0000000..7bb1fc1
--- /dev/null
+++ b/tests/unit/application/test_list_posts.py
@@ -0,0 +1,225 @@
+"""Tests for ListPostsUseCase.
+
+Tests listing posts with various filters.
+"""
+
+from datetime import datetime
+from unittest.mock import AsyncMock, MagicMock
+from uuid import uuid4
+
+import pytest
+
+from app.application.dtos import PostResponseDTO
+from app.application.interfaces import TransactionManager
+from app.application.use_cases.list_posts import ListPostsUseCase
+from app.domain.entities import Post
+from app.domain.repositories import PostRepository
+from app.domain.value_objects import Content, Slug, Title
+
+
+@pytest.fixture
+def mock_post_repository() -> MagicMock:
+    """Create mock post repository."""
+    return MagicMock(spec=PostRepository)
+
+
+@pytest.fixture
+def mock_transaction_manager() -> MagicMock:
+    """Create mock transaction manager."""
+    return MagicMock(spec=TransactionManager)
+
+
+@pytest.fixture
+def list_use_case(
+    mock_post_repository: MagicMock,
+    mock_transaction_manager: MagicMock,
+) -> ListPostsUseCase:
+    """Create list use case with mocked dependencies."""
+    return ListPostsUseCase(mock_post_repository, mock_transaction_manager)
+
+
+@pytest.fixture
+def sample_posts() -> list[Post]:
+    """Create sample posts for testing."""
+    return [
+        Post(
+            id=uuid4(),
+            title=Title(f"Post {i}"),
+            content=Content(f"Content for post number {i}"),
+            slug=Slug(f"post-{i}"),
+            author_id="author-123",
+            published=i % 2 == 0,
+            tags=["python"] if i == 0 else [],
+            created_at=datetime.now(),
+            updated_at=datetime.now(),
+        )
+        for i in range(3)
+    ]
+
+
+class TestAllPosts:
+    """Test suite for all_posts method."""
+
+    async def test_all_posts(
+        self,
+        list_use_case: ListPostsUseCase,
+        mock_post_repository: MagicMock,
+        sample_posts: list[Post],
+    ) -> None:
+        """Test getting all posts."""
+        mock_post_repository.get_all = AsyncMock(return_value=sample_posts)
+
+        result = await list_use_case.all_posts()
+
+        assert len(result) == 3
+        assert all(isinstance(dto, PostResponseDTO) for dto in result)
+        mock_post_repository.get_all.assert_called_once()
+
+    async def test_all_posts_empty(
+        self,
+        list_use_case: ListPostsUseCase,
+        mock_post_repository: MagicMock,
+    ) -> None:
+        """Test getting all posts when empty."""
+        mock_post_repository.get_all = AsyncMock(return_value=[])
+
+        result = await list_use_case.all_posts()
+
+        assert result == []
+
+
+class TestPublishedPosts:
+    """Test suite for published_posts method."""
+
+    async def test_published_posts(
+        self,
+        list_use_case: ListPostsUseCase,
+        mock_post_repository: MagicMock,
+        sample_posts: list[Post],
+    ) -> None:
+        """Test getting published posts."""
+        published = [p for p in sample_posts if p.published]
+        mock_post_repository.get_published = AsyncMock(return_value=published)
+
+        result = await list_use_case.published_posts()
+
+        assert len(result) == 2  # posts 0 and 2 are published
+        assert all(dto.published for dto in result)
+
+    async def test_published_posts_with_limit_offset(
+        self,
+        list_use_case: ListPostsUseCase,
+        mock_post_repository: MagicMock,
+    ) -> None:
+        """Test getting published posts with pagination."""
+        mock_post_repository.get_published = AsyncMock(return_value=[])
+
+        result = await list_use_case.published_posts(limit=5, offset=10)
+
+        mock_post_repository.get_published.assert_called_once_with(limit=5, offset=10)
+        assert result == []
+
+
+class TestByAuthor:
+    """Test suite for by_author method."""
+
+    async def test_by_author(
+        self,
+        list_use_case: ListPostsUseCase,
+        mock_post_repository: MagicMock,
+        sample_posts: list[Post],
+    ) -> None:
+        """Test getting posts by author."""
+        mock_post_repository.get_by_author = AsyncMock(return_value=sample_posts)
+
+        result = await list_use_case.by_author("author-123")
+
+        assert len(result) == 3
+        mock_post_repository.get_by_author.assert_called_once_with(
+            "author-123", limit=None, offset=None
+        )
+
+    async def test_by_author_with_pagination(
+        self,
+        list_use_case: ListPostsUseCase,
+        mock_post_repository: MagicMock,
+    ) -> None:
+        """Test getting posts by author with pagination."""
+        mock_post_repository.get_by_author = AsyncMock(return_value=[])
+
+        await list_use_case.by_author("author-123", limit=5, offset=0)
+
+        mock_post_repository.get_by_author.assert_called_once_with("author-123", limit=5, offset=0)
+
+
+class TestByTag:
+    """Test suite for by_tag method."""
+
+    async def test_by_tag(
+        self,
+        list_use_case: ListPostsUseCase,
+        mock_post_repository: MagicMock,
+        sample_posts: list[Post],
+    ) -> None:
+        """Test getting posts by tag."""
+        tagged_posts = [sample_posts[0]]
+        mock_post_repository.get_by_tag = AsyncMock(return_value=tagged_posts)
+
+        result = await list_use_case.by_tag("python")
+
+        assert len(result) == 1
+        assert "python" in result[0].tags
+
+    async def test_by_tag_empty(
+        self,
+        list_use_case: ListPostsUseCase,
+        mock_post_repository: MagicMock,
+    ) -> None:
+        """Test getting posts by non-existent tag."""
+        mock_post_repository.get_by_tag = AsyncMock(return_value=[])
+
+        result = await list_use_case.by_tag("nonexistent")
+
+        assert result == []
+
+
+class TestSearch:
+    """Test suite for search method."""
+
+    async def test_search(
+        self,
+        list_use_case: ListPostsUseCase,
+        mock_post_repository: MagicMock,
+        sample_posts: list[Post],
+    ) -> None:
+        """Test searching posts."""
+        mock_post_repository.search = AsyncMock(return_value=sample_posts)
+
+        result = await list_use_case.search("test query")
+
+        assert len(result) == 3
+        mock_post_repository.search.assert_called_once_with("test query", limit=None, offset=None)
+
+    async def test_search_with_pagination(
+        self,
+        list_use_case: ListPostsUseCase,
+        mock_post_repository: MagicMock,
+    ) -> None:
+        """Test searching posts with pagination."""
+        mock_post_repository.search = AsyncMock(return_value=[])
+
+        await list_use_case.search("query", limit=10, offset=5)
+
+        mock_post_repository.search.assert_called_once_with("query", limit=10, offset=5)
+
+    async def test_search_no_results(
+        self,
+        list_use_case: ListPostsUseCase,
+        mock_post_repository: MagicMock,
+    ) -> None:
+        """Test searching with no matches."""
+        mock_post_repository.search = AsyncMock(return_value=[])
+
+        result = await list_use_case.search("xyz123")
+
+        assert result == []
diff --git a/tests/unit/application/test_publish_post.py b/tests/unit/application/test_publish_post.py
new file mode 100644
index 0000000..9e05644
--- /dev/null
+++ b/tests/unit/application/test_publish_post.py
@@ -0,0 +1,174 @@
+"""Tests for PublishPostUseCase.
+
+Tests publishing and unpublishing posts with authorization.
+"""
+
+from datetime import datetime
+from unittest.mock import AsyncMock, MagicMock
+from uuid import uuid4
+
+import pytest
+
+from app.application.dtos import PostResponseDTO
+from app.application.interfaces import TransactionManager
+from app.application.use_cases.publish_post import PublishPostUseCase
+from app.domain.entities import Post
+from app.domain.exceptions import ForbiddenException, NotFoundException
+from app.domain.repositories import PostRepository
+from app.domain.value_objects import Content, Slug, Title
+
+
+@pytest.fixture
+def mock_post_repository() -> MagicMock:
+    """Create mock post repository."""
+    return MagicMock(spec=PostRepository)
+
+
+@pytest.fixture
+def mock_transaction_manager() -> MagicMock:
+    """Create mock transaction manager."""
+    tx = MagicMock(spec=TransactionManager)
+    tx.commit = AsyncMock()
+    return tx
+
+
+@pytest.fixture
+def publish_use_case(
+    mock_post_repository: MagicMock,
+    mock_transaction_manager: MagicMock,
+) -> PublishPostUseCase:
+    """Create publish use case with mocked dependencies."""
+    return PublishPostUseCase(mock_post_repository, mock_transaction_manager)
+
+
+@pytest.fixture
+def sample_post() -> Post:
+    """Create a sample unpublished post."""
+    return Post(
+        id=uuid4(),
+        title=Title("Test Post"),
+        content=Content("Test content"),
+        slug=Slug("test-post"),
+        author_id="author-123",
+        published=False,
+        tags=["test"],
+        created_at=datetime.now(),
+        updated_at=datetime.now(),
+    )
+
+
+@pytest.fixture
+def published_post() -> Post:
+    """Create a sample published post."""
+    post = Post(
+        id=uuid4(),
+        title=Title("Published Post"),
+        content=Content("Published content"),
+        slug=Slug("published-post"),
+        author_id="author-123",
+        published=True,
+        tags=["published"],
+        created_at=datetime.now(),
+        updated_at=datetime.now(),
+    )
+    return post
+
+
+class TestPublishPost:
+    """Test suite for publish method."""
+
+    async def test_publish_success(
+        self,
+        publish_use_case: PublishPostUseCase,
+        mock_post_repository: MagicMock,
+        mock_transaction_manager: MagicMock,
+        sample_post: Post,
+    ) -> None:
+        """Test successful post publishing."""
+        mock_post_repository.get_by_id = AsyncMock(return_value=sample_post)
+        mock_post_repository.update = AsyncMock()
+
+        result = await publish_use_case.publish(sample_post.id, sample_post.author_id)
+
+        assert isinstance(result, PostResponseDTO)
+        assert result.id == sample_post.id
+        assert result.published is True
+        mock_post_repository.update.assert_called_once()
+        mock_transaction_manager.commit.assert_called_once()
+
+    async def test_publish_not_found(
+        self,
+        publish_use_case: PublishPostUseCase,
+        mock_post_repository: MagicMock,
+    ) -> None:
+        """Test publishing non-existent post raises NotFoundException."""
+        mock_post_repository.get_by_id = AsyncMock(return_value=None)
+
+        with pytest.raises(NotFoundException) as exc_info:
+            await publish_use_case.publish(uuid4(), "author-123")
+
+        assert "not found" in str(exc_info.value).lower()
+
+    async def test_publish_forbidden(
+        self,
+        publish_use_case: PublishPostUseCase,
+        mock_post_repository: MagicMock,
+        sample_post: Post,
+    ) -> None:
+        """Test publishing other user's post raises ForbiddenException."""
+        mock_post_repository.get_by_id = AsyncMock(return_value=sample_post)
+
+        with pytest.raises(ForbiddenException) as exc_info:
+            await publish_use_case.publish(sample_post.id, "different-author")
+
+        assert "own posts" in str(exc_info.value).lower()
+
+
+class TestUnpublishPost:
+    """Test suite for unpublish method."""
+
+    async def test_unpublish_success(
+        self,
+        publish_use_case: PublishPostUseCase,
+        mock_post_repository: MagicMock,
+        mock_transaction_manager: MagicMock,
+        published_post: Post,
+    ) -> None:
+        """Test successful post unpublishing."""
+        mock_post_repository.get_by_id = AsyncMock(return_value=published_post)
+        mock_post_repository.update = AsyncMock()
+
+        result = await publish_use_case.unpublish(published_post.id, published_post.author_id)
+
+        assert isinstance(result, PostResponseDTO)
+        assert result.id == published_post.id
+        assert result.published is False
+        mock_post_repository.update.assert_called_once()
+        mock_transaction_manager.commit.assert_called_once()
+
+    async def test_unpublish_not_found(
+        self,
+        publish_use_case: PublishPostUseCase,
+        mock_post_repository: MagicMock,
+    ) -> None:
+        """Test unpublishing non-existent post raises NotFoundException."""
+        mock_post_repository.get_by_id = AsyncMock(return_value=None)
+
+        with pytest.raises(NotFoundException) as exc_info:
+            await publish_use_case.unpublish(uuid4(), "author-123")
+
+        assert "not found" in str(exc_info.value).lower()
+
+    async def test_unpublish_forbidden(
+        self,
+        publish_use_case: PublishPostUseCase,
+        mock_post_repository: MagicMock,
+        published_post: Post,
+    ) -> None:
+        """Test unpublishing other user's post raises ForbiddenException."""
+        mock_post_repository.get_by_id = AsyncMock(return_value=published_post)
+
+        with pytest.raises(ForbiddenException) as exc_info:
+            await publish_use_case.unpublish(published_post.id, "different-author")
+
+        assert "own posts" in str(exc_info.value).lower()
diff --git a/tests/unit/infrastructure/test_transaction_manager.py b/tests/unit/infrastructure/test_transaction_manager.py
new file mode 100644
index 0000000..6b0154b
--- /dev/null
+++ b/tests/unit/infrastructure/test_transaction_manager.py
@@ -0,0 +1,46 @@
+"""Tests for DI transaction manager.
+
+Tests SessionTransactionManager implementation.
+"""
+
+from unittest.mock import AsyncMock, MagicMock
+
+import pytest
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.infrastructure.di.transaction_manager import SessionTransactionManager
+
+
+@pytest.fixture
+def mock_session() -> MagicMock:
+    """Create mock async session."""
+    session = MagicMock(spec=AsyncSession)
+    session.commit = AsyncMock()
+    session.rollback = AsyncMock()
+    return session
+
+
+@pytest.fixture
+def transaction_manager(mock_session: MagicMock) -> SessionTransactionManager:
+    """Create transaction manager with mock session."""
+    return SessionTransactionManager(mock_session)
+
+
+class TestSessionTransactionManager:
+    """Test suite for SessionTransactionManager."""
+
+    async def test_commit(
+        self, transaction_manager: SessionTransactionManager, mock_session: MagicMock
+    ) -> None:
+        """Test commit calls session commit."""
+        await transaction_manager.commit()
+
+        mock_session.commit.assert_called_once()
+
+    async def test_rollback(
+        self, transaction_manager: SessionTransactionManager, mock_session: MagicMock
+    ) -> None:
+        """Test rollback calls session rollback."""
+        await transaction_manager.rollback()
+
+        mock_session.rollback.assert_called_once()