diff --git a/api/tests/test_containers_integration_tests/services/test_file_service.py b/api/tests/test_containers_integration_tests/services/test_file_service.py
new file mode 100644
index 000000000..965c9c624
--- /dev/null
+++ b/api/tests/test_containers_integration_tests/services/test_file_service.py
@@ -0,0 +1,913 @@
+import hashlib
+from io import BytesIO
+from unittest.mock import patch
+
+import pytest
+from faker import Faker
+from werkzeug.exceptions import NotFound
+
+from configs import dify_config
+from models.account import Account, Tenant
+from models.enums import CreatorUserRole
+from models.model import EndUser, UploadFile
+from services.errors.file import FileTooLargeError, UnsupportedFileTypeError
+from services.file_service import FileService
+
+
+class TestFileService:
+    """Integration tests for FileService using testcontainers."""
+
+    @pytest.fixture
+    def mock_external_service_dependencies(self):
+        """Mock setup for external service dependencies."""
+        with (
+            patch("services.file_service.storage") as mock_storage,
+            patch("services.file_service.file_helpers") as mock_file_helpers,
+            patch("services.file_service.ExtractProcessor") as mock_extract_processor,
+        ):
+            # Setup default mock returns
+            mock_storage.save.return_value = None
+            mock_storage.load.return_value = BytesIO(b"mock file content")
+            mock_file_helpers.get_signed_file_url.return_value = "https://example.com/signed-url"
+            mock_file_helpers.verify_image_signature.return_value = True
+            mock_file_helpers.verify_file_signature.return_value = True
+            mock_extract_processor.load_from_upload_file.return_value = "extracted text content"
+
+            yield {
+                "storage": mock_storage,
+                "file_helpers": mock_file_helpers,
+                "extract_processor": mock_extract_processor,
+            }
+
+    def _create_test_account(self, db_session_with_containers, mock_external_service_dependencies):
+        """
+        Helper method to create a test account for testing.
+
+        Args:
+            db_session_with_containers: Database session from testcontainers infrastructure
+            mock_external_service_dependencies: Mock dependencies
+
+        Returns:
+            Account: Created account instance
+        """
+        fake = Faker()
+
+        # Create account
+        account = Account(
+            email=fake.email(),
+            name=fake.name(),
+            interface_language="en-US",
+            status="active",
+        )
+
+        from extensions.ext_database import db
+
+        db.session.add(account)
+        db.session.commit()
+
+        # Create tenant for the account
+        tenant = Tenant(
+            name=fake.company(),
+            status="normal",
+        )
+        db.session.add(tenant)
+        db.session.commit()
+
+        # Create tenant-account join
+        from models.account import TenantAccountJoin, TenantAccountRole
+
+        join = TenantAccountJoin(
+            tenant_id=tenant.id,
+            account_id=account.id,
+            role=TenantAccountRole.OWNER.value,
+            current=True,
+        )
+        db.session.add(join)
+        db.session.commit()
+
+        # Set current tenant for account
+        account.current_tenant = tenant
+
+        return account
+
+    def _create_test_end_user(self, db_session_with_containers, mock_external_service_dependencies):
+        """
+        Helper method to create a test end user for testing.
+
+        Args:
+            db_session_with_containers: Database session from testcontainers infrastructure
+            mock_external_service_dependencies: Mock dependencies
+
+        Returns:
+            EndUser: Created end user instance
+        """
+        fake = Faker()
+
+        end_user = EndUser(
+            tenant_id=str(fake.uuid4()),
+            type="web",
+            name=fake.name(),
+            is_anonymous=False,
+            session_id=fake.uuid4(),
+        )
+
+        from extensions.ext_database import db
+
+        db.session.add(end_user)
+        db.session.commit()
+
+        return end_user
+
+    def _create_test_upload_file(self, db_session_with_containers, mock_external_service_dependencies, account):
+        """
+        Helper method to create a test upload file for testing.
+
+        Args:
+            db_session_with_containers: Database session from testcontainers infrastructure
+            mock_external_service_dependencies: Mock dependencies
+            account: Account instance
+
+        Returns:
+            UploadFile: Created upload file instance
+        """
+        fake = Faker()
+
+        upload_file = UploadFile(
+            tenant_id=account.current_tenant_id if hasattr(account, "current_tenant_id") else str(fake.uuid4()),
+            storage_type="local",
+            key=f"upload_files/test/{fake.uuid4()}.txt",
+            name="test_file.txt",
+            size=1024,
+            extension="txt",
+            mime_type="text/plain",
+            created_by_role=CreatorUserRole.ACCOUNT,
+            created_by=account.id,
+            created_at=fake.date_time(),
+            used=False,
+            hash=hashlib.sha3_256(b"test content").hexdigest(),
+            source_url="",
+        )
+
+        from extensions.ext_database import db
+
+        db.session.add(upload_file)
+        db.session.commit()
+
+        return upload_file
+
+    # Test upload_file method
+    def test_upload_file_success(self, db_session_with_containers, mock_external_service_dependencies):
+        """
+        Test successful file upload with valid parameters.
+        """
+        fake = Faker()
+        account = self._create_test_account(db_session_with_containers, mock_external_service_dependencies)
+
+        filename = "test_document.pdf"
+        content = b"test file content"
+        mimetype = "application/pdf"
+
+        upload_file = FileService.upload_file(
+            filename=filename,
+            content=content,
+            mimetype=mimetype,
+            user=account,
+        )
+
+        assert upload_file is not None
+        assert upload_file.name == filename
+        assert upload_file.size == len(content)
+        assert upload_file.extension == "pdf"
+        assert upload_file.mime_type == mimetype
+        assert upload_file.created_by == account.id
+        assert upload_file.created_by_role == CreatorUserRole.ACCOUNT.value
+        assert upload_file.used is False
+        assert upload_file.hash == hashlib.sha3_256(content).hexdigest()
+
+        # Verify storage was called
+        mock_external_service_dependencies["storage"].save.assert_called_once()
+
+        # Verify database state
+        from extensions.ext_database import db
+
+        db.session.refresh(upload_file)
+        assert upload_file.id is not None
+
+    def test_upload_file_with_end_user(self, db_session_with_containers, mock_external_service_dependencies):
+        """
+        Test file upload with end user instead of account.
+        """
+        fake = Faker()
+        end_user = self._create_test_end_user(db_session_with_containers, mock_external_service_dependencies)
+
+        filename = "test_image.jpg"
+        content = b"test image content"
+        mimetype = "image/jpeg"
+
+        upload_file = FileService.upload_file(
+            filename=filename,
+            content=content,
+            mimetype=mimetype,
+            user=end_user,
+        )
+
+        assert upload_file is not None
+        assert upload_file.created_by == end_user.id
+        assert upload_file.created_by_role == CreatorUserRole.END_USER.value
+
+    def test_upload_file_with_datasets_source(self, db_session_with_containers, mock_external_service_dependencies):
+        """
+        Test file upload with datasets source parameter.
+        """
+        fake = Faker()
+        account = self._create_test_account(db_session_with_containers, mock_external_service_dependencies)
+
+        filename = "test_document.pdf"
+        content = b"test file content"
+        mimetype = "application/pdf"
+
+        upload_file = FileService.upload_file(
+            filename=filename,
+            content=content,
+            mimetype=mimetype,
+            user=account,
+            source="datasets",
+            source_url="https://example.com/source",
+        )
+
+        assert upload_file is not None
+        assert upload_file.source_url == "https://example.com/source"
+
+    def test_upload_file_invalid_filename_characters(
+        self, db_session_with_containers, mock_external_service_dependencies
+    ):
+        """
+        Test file upload with invalid filename characters.
+        """
+        fake = Faker()
+        account = self._create_test_account(db_session_with_containers, mock_external_service_dependencies)
+
+        filename = "test/file<name>.txt"
+        content = b"test content"
+        mimetype = "text/plain"
+
+        with pytest.raises(ValueError, match="Filename contains invalid characters"):
+            FileService.upload_file(
+                filename=filename,
+                content=content,
+                mimetype=mimetype,
+                user=account,
+            )
+
+    def test_upload_file_filename_too_long(self, db_session_with_containers, mock_external_service_dependencies):
+        """
+        Test file upload with filename that exceeds length limit.
+        """
+        fake = Faker()
+        account = self._create_test_account(db_session_with_containers, mock_external_service_dependencies)
+
+        # Create a filename longer than 200 characters
+        long_name = "a" * 250
+        filename = f"{long_name}.txt"
+        content = b"test content"
+        mimetype = "text/plain"
+
+        upload_file = FileService.upload_file(
+            filename=filename,
+            content=content,
+            mimetype=mimetype,
+            user=account,
+        )
+
+        # Verify filename was truncated (the logic truncates the base name to 200 chars + extension)
+        # So the total length should be <= 200 + len(extension) + 1 (for the dot)
+        assert len(upload_file.name) <= 200 + len(upload_file.extension) + 1
+        assert upload_file.name.endswith(".txt")
+        # Verify the base name was truncated
+        base_name = upload_file.name[:-4]  # Remove .txt
+        assert len(base_name) <= 200
+
+    def test_upload_file_datasets_unsupported_type(
+        self, db_session_with_containers, mock_external_service_dependencies
+    ):
+        """
+        Test file upload for datasets with unsupported file type.
+        """
+        fake = Faker()
+        account = self._create_test_account(db_session_with_containers, mock_external_service_dependencies)
+
+        filename = "test_image.jpg"
+        content = b"test content"
+        mimetype = "image/jpeg"
+
+        with pytest.raises(UnsupportedFileTypeError):
+            FileService.upload_file(
+                filename=filename,
+                content=content,
+                mimetype=mimetype,
+                user=account,
+                source="datasets",
+            )
+
+    def test_upload_file_too_large(self, db_session_with_containers, mock_external_service_dependencies):
+        """
+        Test file upload with file size exceeding limit.
+        """
+        fake = Faker()
+        account = self._create_test_account(db_session_with_containers, mock_external_service_dependencies)
+
+        filename = "large_image.jpg"
+        # Create content larger than the limit
+        content = b"x" * (dify_config.UPLOAD_IMAGE_FILE_SIZE_LIMIT * 1024 * 1024 + 1)
+        mimetype = "image/jpeg"
+
+        with pytest.raises(FileTooLargeError):
+            FileService.upload_file(
+                filename=filename,
+                content=content,
+                mimetype=mimetype,
+                user=account,
+            )
+
+    # Test is_file_size_within_limit method
+    def test_is_file_size_within_limit_image_success(
+        self, db_session_with_containers, mock_external_service_dependencies
+    ):
+        """
+        Test file size check for image files within limit.
+        """
+        extension = "jpg"
+        file_size = dify_config.UPLOAD_IMAGE_FILE_SIZE_LIMIT * 1024 * 1024  # Exactly at limit
+
+        result = FileService.is_file_size_within_limit(extension=extension, file_size=file_size)
+
+        assert result is True
+
+    def test_is_file_size_within_limit_video_success(
+        self, db_session_with_containers, mock_external_service_dependencies
+    ):
+        """
+        Test file size check for video files within limit.
+        """
+        extension = "mp4"
+        file_size = dify_config.UPLOAD_VIDEO_FILE_SIZE_LIMIT * 1024 * 1024  # Exactly at limit
+
+        result = FileService.is_file_size_within_limit(extension=extension, file_size=file_size)
+
+        assert result is True
+
+    def test_is_file_size_within_limit_audio_success(
+        self, db_session_with_containers, mock_external_service_dependencies
+    ):
+        """
+        Test file size check for audio files within limit.
+        """
+        extension = "mp3"
+        file_size = dify_config.UPLOAD_AUDIO_FILE_SIZE_LIMIT * 1024 * 1024  # Exactly at limit
+
+        result = FileService.is_file_size_within_limit(extension=extension, file_size=file_size)
+
+        assert result is True
+
+    def test_is_file_size_within_limit_document_success(
+        self, db_session_with_containers, mock_external_service_dependencies
+    ):
+        """
+        Test file size check for document files within limit.
+        """
+        extension = "pdf"
+        file_size = dify_config.UPLOAD_FILE_SIZE_LIMIT * 1024 * 1024  # Exactly at limit
+
+        result = FileService.is_file_size_within_limit(extension=extension, file_size=file_size)
+
+        assert result is True
+
+    def test_is_file_size_within_limit_image_exceeded(
+        self, db_session_with_containers, mock_external_service_dependencies
+    ):
+        """
+        Test file size check for image files exceeding limit.
+        """
+        extension = "jpg"
+        file_size = dify_config.UPLOAD_IMAGE_FILE_SIZE_LIMIT * 1024 * 1024 + 1  # Exceeds limit
+
+        result = FileService.is_file_size_within_limit(extension=extension, file_size=file_size)
+
+        assert result is False
+
+    def test_is_file_size_within_limit_unknown_extension(
+        self, db_session_with_containers, mock_external_service_dependencies
+    ):
+        """
+        Test file size check for unknown file extension.
+        """
+        extension = "xyz"
+        file_size = dify_config.UPLOAD_FILE_SIZE_LIMIT * 1024 * 1024  # Uses default limit
+
+        result = FileService.is_file_size_within_limit(extension=extension, file_size=file_size)
+
+        assert result is True
+
+    # Test upload_text method
+    def test_upload_text_success(self, db_session_with_containers, mock_external_service_dependencies):
+        """
+        Test successful text upload.
+        """
+        fake = Faker()
+        text = "This is a test text content"
+        text_name = "test_text.txt"
+
+        # Mock current_user
+        with patch("services.file_service.current_user") as mock_current_user:
+            mock_current_user.current_tenant_id = str(fake.uuid4())
+            mock_current_user.id = str(fake.uuid4())
+
+            upload_file = FileService.upload_text(text=text, text_name=text_name)
+
+            assert upload_file is not None
+            assert upload_file.name == text_name
+            assert upload_file.size == len(text)
+            assert upload_file.extension == "txt"
+            assert upload_file.mime_type == "text/plain"
+            assert upload_file.used is True
+            assert upload_file.used_by == mock_current_user.id
+
+            # Verify storage was called
+            mock_external_service_dependencies["storage"].save.assert_called_once()
+
+    def test_upload_text_name_too_long(self, db_session_with_containers, mock_external_service_dependencies):
+        """
+        Test text upload with name that exceeds length limit.
+        """
+        fake = Faker()
+        text = "test content"
+        long_name = "a" * 250  # Longer than 200 characters
+
+        # Mock current_user
+        with patch("services.file_service.current_user") as mock_current_user:
+            mock_current_user.current_tenant_id = str(fake.uuid4())
+            mock_current_user.id = str(fake.uuid4())
+
+            upload_file = FileService.upload_text(text=text, text_name=long_name)
+
+            # Verify name was truncated
+            assert len(upload_file.name) <= 200
+            assert upload_file.name == "a" * 200
+
+    # Test get_file_preview method
+    def test_get_file_preview_success(self, db_session_with_containers, mock_external_service_dependencies):
+        """
+        Test successful file preview generation.
+        """
+        fake = Faker()
+        account = self._create_test_account(db_session_with_containers, mock_external_service_dependencies)
+        upload_file = self._create_test_upload_file(
+            db_session_with_containers, mock_external_service_dependencies, account
+        )
+
+        # Update file to have document extension
+        upload_file.extension = "pdf"
+        from extensions.ext_database import db
+
+        db.session.commit()
+
+        result = FileService.get_file_preview(file_id=upload_file.id)
+
+        assert result == "extracted text content"
+        mock_external_service_dependencies["extract_processor"].load_from_upload_file.assert_called_once()
+
+    def test_get_file_preview_file_not_found(self, db_session_with_containers, mock_external_service_dependencies):
+        """
+        Test file preview with non-existent file.
+        """
+        fake = Faker()
+        non_existent_id = str(fake.uuid4())
+
+        with pytest.raises(NotFound, match="File not found"):
+            FileService.get_file_preview(file_id=non_existent_id)
+
+    def test_get_file_preview_unsupported_file_type(
+        self, db_session_with_containers, mock_external_service_dependencies
+    ):
+        """
+        Test file preview with unsupported file type.
+        """
+        fake = Faker()
+        account = self._create_test_account(db_session_with_containers, mock_external_service_dependencies)
+        upload_file = self._create_test_upload_file(
+            db_session_with_containers, mock_external_service_dependencies, account
+        )
+
+        # Update file to have non-document extension
+        upload_file.extension = "jpg"
+        from extensions.ext_database import db
+
+        db.session.commit()
+
+        with pytest.raises(UnsupportedFileTypeError):
+            FileService.get_file_preview(file_id=upload_file.id)
+
+    def test_get_file_preview_text_truncation(self, db_session_with_containers, mock_external_service_dependencies):
+        """
+        Test file preview with text that exceeds preview limit.
+        """
+        fake = Faker()
+        account = self._create_test_account(db_session_with_containers, mock_external_service_dependencies)
+        upload_file = self._create_test_upload_file(
+            db_session_with_containers, mock_external_service_dependencies, account
+        )
+
+        # Update file to have document extension
+        upload_file.extension = "pdf"
+        from extensions.ext_database import db
+
+        db.session.commit()
+
+        # Mock long text content
+        long_text = "x" * 5000  # Longer than PREVIEW_WORDS_LIMIT
+        mock_external_service_dependencies["extract_processor"].load_from_upload_file.return_value = long_text
+
+        result = FileService.get_file_preview(file_id=upload_file.id)
+
+        assert len(result) == 3000  # PREVIEW_WORDS_LIMIT
+        assert result == "x" * 3000
+
+    # Test get_image_preview method
+    def test_get_image_preview_success(self, db_session_with_containers, mock_external_service_dependencies):
+        """
+        Test successful image preview generation.
+        """
+        fake = Faker()
+        account = self._create_test_account(db_session_with_containers, mock_external_service_dependencies)
+        upload_file = self._create_test_upload_file(
+            db_session_with_containers, mock_external_service_dependencies, account
+        )
+
+        # Update file to have image extension
+        upload_file.extension = "jpg"
+        from extensions.ext_database import db
+
+        db.session.commit()
+
+        timestamp = "1234567890"
+        nonce = "test_nonce"
+        sign = "test_signature"
+
+        generator, mime_type = FileService.get_image_preview(
+            file_id=upload_file.id,
+            timestamp=timestamp,
+            nonce=nonce,
+            sign=sign,
+        )
+
+        assert generator is not None
+        assert mime_type == upload_file.mime_type
+        mock_external_service_dependencies["file_helpers"].verify_image_signature.assert_called_once()
+
+    def test_get_image_preview_invalid_signature(self, db_session_with_containers, mock_external_service_dependencies):
+        """
+        Test image preview with invalid signature.
+        """
+        fake = Faker()
+        account = self._create_test_account(db_session_with_containers, mock_external_service_dependencies)
+        upload_file = self._create_test_upload_file(
+            db_session_with_containers, mock_external_service_dependencies, account
+        )
+
+        # Mock invalid signature
+        mock_external_service_dependencies["file_helpers"].verify_image_signature.return_value = False
+
+        timestamp = "1234567890"
+        nonce = "test_nonce"
+        sign = "invalid_signature"
+
+        with pytest.raises(NotFound, match="File not found or signature is invalid"):
+            FileService.get_image_preview(
+                file_id=upload_file.id,
+                timestamp=timestamp,
+                nonce=nonce,
+                sign=sign,
+            )
+
+    def test_get_image_preview_file_not_found(self, db_session_with_containers, mock_external_service_dependencies):
+        """
+        Test image preview with non-existent file.
+        """
+        fake = Faker()
+        non_existent_id = str(fake.uuid4())
+
+        timestamp = "1234567890"
+        nonce = "test_nonce"
+        sign = "test_signature"
+
+        with pytest.raises(NotFound, match="File not found or signature is invalid"):
+            FileService.get_image_preview(
+                file_id=non_existent_id,
+                timestamp=timestamp,
+                nonce=nonce,
+                sign=sign,
+            )
+
+    def test_get_image_preview_unsupported_file_type(
+        self, db_session_with_containers, mock_external_service_dependencies
+    ):
+        """
+        Test image preview with non-image file type.
+        """
+        fake = Faker()
+        account = self._create_test_account(db_session_with_containers, mock_external_service_dependencies)
+        upload_file = self._create_test_upload_file(
+            db_session_with_containers, mock_external_service_dependencies, account
+        )
+
+        # Update file to have non-image extension
+        upload_file.extension = "pdf"
+        from extensions.ext_database import db
+
+        db.session.commit()
+
+        timestamp = "1234567890"
+        nonce = "test_nonce"
+        sign = "test_signature"
+
+        with pytest.raises(UnsupportedFileTypeError):
+            FileService.get_image_preview(
+                file_id=upload_file.id,
+                timestamp=timestamp,
+                nonce=nonce,
+                sign=sign,
+            )
+
+    # Test get_file_generator_by_file_id method
+    def test_get_file_generator_by_file_id_success(
+        self, db_session_with_containers, mock_external_service_dependencies
+    ):
+        """
+        Test successful file generator retrieval.
+        """
+        fake = Faker()
+        account = self._create_test_account(db_session_with_containers, mock_external_service_dependencies)
+        upload_file = self._create_test_upload_file(
+            db_session_with_containers, mock_external_service_dependencies, account
+        )
+
+        timestamp = "1234567890"
+        nonce = "test_nonce"
+        sign = "test_signature"
+
+        generator, file_obj = FileService.get_file_generator_by_file_id(
+            file_id=upload_file.id,
+            timestamp=timestamp,
+            nonce=nonce,
+            sign=sign,
+        )
+
+        assert generator is not None
+        assert file_obj == upload_file
+        mock_external_service_dependencies["file_helpers"].verify_file_signature.assert_called_once()
+
+    def test_get_file_generator_by_file_id_invalid_signature(
+        self, db_session_with_containers, mock_external_service_dependencies
+    ):
+        """
+        Test file generator retrieval with invalid signature.
+        """
+        fake = Faker()
+        account = self._create_test_account(db_session_with_containers, mock_external_service_dependencies)
+        upload_file = self._create_test_upload_file(
+            db_session_with_containers, mock_external_service_dependencies, account
+        )
+
+        # Mock invalid signature
+        mock_external_service_dependencies["file_helpers"].verify_file_signature.return_value = False
+
+        timestamp = "1234567890"
+        nonce = "test_nonce"
+        sign = "invalid_signature"
+
+        with pytest.raises(NotFound, match="File not found or signature is invalid"):
+            FileService.get_file_generator_by_file_id(
+                file_id=upload_file.id,
+                timestamp=timestamp,
+                nonce=nonce,
+                sign=sign,
+            )
+
+    def test_get_file_generator_by_file_id_file_not_found(
+        self, db_session_with_containers, mock_external_service_dependencies
+    ):
+        """
+        Test file generator retrieval with non-existent file.
+        """
+        fake = Faker()
+        non_existent_id = str(fake.uuid4())
+
+        timestamp = "1234567890"
+        nonce = "test_nonce"
+        sign = "test_signature"
+
+        with pytest.raises(NotFound, match="File not found or signature is invalid"):
+            FileService.get_file_generator_by_file_id(
+                file_id=non_existent_id,
+                timestamp=timestamp,
+                nonce=nonce,
+                sign=sign,
+            )
+
+    # Test get_public_image_preview method
+    def test_get_public_image_preview_success(self, db_session_with_containers, mock_external_service_dependencies):
+        """
+        Test successful public image preview generation.
+        """
+        fake = Faker()
+        account = self._create_test_account(db_session_with_containers, mock_external_service_dependencies)
+        upload_file = self._create_test_upload_file(
+            db_session_with_containers, mock_external_service_dependencies, account
+        )
+
+        # Update file to have image extension
+        upload_file.extension = "jpg"
+        from extensions.ext_database import db
+
+        db.session.commit()
+
+        generator, mime_type = FileService.get_public_image_preview(file_id=upload_file.id)
+
+        assert generator is not None
+        assert mime_type == upload_file.mime_type
+        mock_external_service_dependencies["storage"].load.assert_called_once()
+
+    def test_get_public_image_preview_file_not_found(
+        self, db_session_with_containers, mock_external_service_dependencies
+    ):
+        """
+        Test public image preview with non-existent file.
+        """
+        fake = Faker()
+        non_existent_id = str(fake.uuid4())
+
+        with pytest.raises(NotFound, match="File not found or signature is invalid"):
+            FileService.get_public_image_preview(file_id=non_existent_id)
+
+    def test_get_public_image_preview_unsupported_file_type(
+        self, db_session_with_containers, mock_external_service_dependencies
+    ):
+        """
+        Test public image preview with non-image file type.
+        """
+        fake = Faker()
+        account = self._create_test_account(db_session_with_containers, mock_external_service_dependencies)
+        upload_file = self._create_test_upload_file(
+            db_session_with_containers, mock_external_service_dependencies, account
+        )
+
+        # Update file to have non-image extension
+        upload_file.extension = "pdf"
+        from extensions.ext_database import db
+
+        db.session.commit()
+
+        with pytest.raises(UnsupportedFileTypeError):
+            FileService.get_public_image_preview(file_id=upload_file.id)
+
+    # Test edge cases and boundary conditions
+    def test_upload_file_empty_content(self, db_session_with_containers, mock_external_service_dependencies):
+        """
+        Test file upload with empty content.
+        """
+        fake = Faker()
+        account = self._create_test_account(db_session_with_containers, mock_external_service_dependencies)
+
+        filename = "empty.txt"
+        content = b""
+        mimetype = "text/plain"
+
+        upload_file = FileService.upload_file(
+            filename=filename,
+            content=content,
+            mimetype=mimetype,
+            user=account,
+        )
+
+        assert upload_file is not None
+        assert upload_file.size == 0
+
+    def test_upload_file_special_characters_in_name(
+        self, db_session_with_containers, mock_external_service_dependencies
+    ):
+        """
+        Test file upload with special characters in filename (but valid ones).
+        """
+        fake = Faker()
+        account = self._create_test_account(db_session_with_containers, mock_external_service_dependencies)
+
+        filename = "test-file_with_underscores_and.dots.txt"
+        content = b"test content"
+        mimetype = "text/plain"
+
+        upload_file = FileService.upload_file(
+            filename=filename,
+            content=content,
+            mimetype=mimetype,
+            user=account,
+        )
+
+        assert upload_file is not None
+        assert upload_file.name == filename
+
+    def test_upload_file_different_case_extensions(
+        self, db_session_with_containers, mock_external_service_dependencies
+    ):
+        """
+        Test file upload with different case extensions.
+        """
+        fake = Faker()
+        account = self._create_test_account(db_session_with_containers, mock_external_service_dependencies)
+
+        filename = "test.PDF"
+        content = b"test content"
+        mimetype = "application/pdf"
+
+        upload_file = FileService.upload_file(
+            filename=filename,
+            content=content,
+            mimetype=mimetype,
+            user=account,
+        )
+
+        assert upload_file is not None
+        assert upload_file.extension == "pdf"  # Should be converted to lowercase
+
+    def test_upload_text_empty_text(self, db_session_with_containers, mock_external_service_dependencies):
+        """
+        Test text upload with empty text.
+        """
+        fake = Faker()
+        text = ""
+        text_name = "empty.txt"
+
+        # Mock current_user
+        with patch("services.file_service.current_user") as mock_current_user:
+            mock_current_user.current_tenant_id = str(fake.uuid4())
+            mock_current_user.id = str(fake.uuid4())
+
+            upload_file = FileService.upload_text(text=text, text_name=text_name)
+
+            assert upload_file is not None
+            assert upload_file.size == 0
+
+    def test_file_size_limits_edge_cases(self, db_session_with_containers, mock_external_service_dependencies):
+        """
+        Test file size limits with edge case values.
+        """
+        # Test exactly at limit
+        for extension, limit_config in [
+            ("jpg", dify_config.UPLOAD_IMAGE_FILE_SIZE_LIMIT),
+            ("mp4", dify_config.UPLOAD_VIDEO_FILE_SIZE_LIMIT),
+            ("mp3", dify_config.UPLOAD_AUDIO_FILE_SIZE_LIMIT),
+            ("pdf", dify_config.UPLOAD_FILE_SIZE_LIMIT),
+        ]:
+            file_size = limit_config * 1024 * 1024
+            result = FileService.is_file_size_within_limit(extension=extension, file_size=file_size)
+            assert result is True
+
+            # Test one byte over limit
+            file_size = limit_config * 1024 * 1024 + 1
+            result = FileService.is_file_size_within_limit(extension=extension, file_size=file_size)
+            assert result is False
+
+    def test_upload_file_with_source_url(self, db_session_with_containers, mock_external_service_dependencies):
+        """
+        Test file upload with source URL that gets overridden by signed URL.
+        """
+        fake = Faker()
+        account = self._create_test_account(db_session_with_containers, mock_external_service_dependencies)
+
+        filename = "test.pdf"
+        content = b"test content"
+        mimetype = "application/pdf"
+        source_url = "https://original-source.com/file.pdf"
+
+        upload_file = FileService.upload_file(
+            filename=filename,
+            content=content,
+            mimetype=mimetype,
+            user=account,
+            source_url=source_url,
+        )
+
+        # When source_url is provided, it should be preserved
+        assert upload_file.source_url == source_url
+
+        # The signed URL should only be set when source_url is empty
+        # Let's test that scenario
+        upload_file2 = FileService.upload_file(
+            filename="test2.pdf",
+            content=b"test content 2",
+            mimetype="application/pdf",
+            user=account,
+            source_url="",  # Empty source_url
+        )
+
+        # Should have the signed URL when source_url is empty
+        assert upload_file2.source_url == "https://example.com/signed-url"