diff --git a/tests/client/test_optionals.py b/tests/client/test_optionals.py
new file mode 100644
index 000000000..81cbd387d
--- /dev/null
+++ b/tests/client/test_optionals.py
@@ -0,0 +1,16 @@
+"""Tests for a2a.client.optionals module."""
+
+import importlib
+import sys
+
+from unittest.mock import patch
+
+
+def test_channel_import_failure():
+    """Test Channel behavior when grpc is not available."""
+    with patch.dict('sys.modules', {'grpc': None, 'grpc.aio': None}):
+        if 'a2a.client.optionals' in sys.modules:
+            del sys.modules['a2a.client.optionals']
+
+        optionals = importlib.import_module('a2a.client.optionals')
+        assert optionals.Channel is None
diff --git a/tests/server/test_models.py b/tests/server/test_models.py
new file mode 100644
index 000000000..64fed1008
--- /dev/null
+++ b/tests/server/test_models.py
@@ -0,0 +1,118 @@
+"""Tests for a2a.server.models module."""
+
+from unittest.mock import MagicMock
+
+from sqlalchemy.orm import DeclarativeBase
+
+from a2a.server.models import (
+    PydanticListType,
+    PydanticType,
+    create_push_notification_config_model,
+    create_task_model,
+)
+from a2a.types import Artifact, TaskState, TaskStatus, TextPart
+
+
+class TestPydanticType:
+    """Tests for PydanticType SQLAlchemy type decorator."""
+
+    def test_process_bind_param_with_pydantic_model(self):
+        pydantic_type = PydanticType(TaskStatus)
+        status = TaskStatus(state=TaskState.working)
+        dialect = MagicMock()
+
+        result = pydantic_type.process_bind_param(status, dialect)
+        assert result['state'] == 'working'
+        assert result['message'] is None
+        # TaskStatus may have other optional fields
+
+    def test_process_bind_param_with_none(self):
+        pydantic_type = PydanticType(TaskStatus)
+        dialect = MagicMock()
+
+        result = pydantic_type.process_bind_param(None, dialect)
+        assert result is None
+
+    def test_process_result_value(self):
+        pydantic_type = PydanticType(TaskStatus)
+        dialect = MagicMock()
+
+        result = pydantic_type.process_result_value(
+            {'state': 'completed', 'message': None}, dialect
+        )
+        assert isinstance(result, TaskStatus)
+        assert result.state == 'completed'
+
+
+class TestPydanticListType:
+    """Tests for PydanticListType SQLAlchemy type decorator."""
+
+    def test_process_bind_param_with_list(self):
+        pydantic_list_type = PydanticListType(Artifact)
+        artifacts = [
+            Artifact(
+                artifact_id='1', parts=[TextPart(type='text', text='Hello')]
+            ),
+            Artifact(
+                artifact_id='2', parts=[TextPart(type='text', text='World')]
+            ),
+        ]
+        dialect = MagicMock()
+
+        result = pydantic_list_type.process_bind_param(artifacts, dialect)
+        assert len(result) == 2
+        assert result[0]['artifactId'] == '1'  # JSON mode uses camelCase
+        assert result[1]['artifactId'] == '2'
+
+    def test_process_result_value_with_list(self):
+        pydantic_list_type = PydanticListType(Artifact)
+        dialect = MagicMock()
+        data = [
+            {'artifact_id': '1', 'parts': [{'type': 'text', 'text': 'Hello'}]},
+            {'artifact_id': '2', 'parts': [{'type': 'text', 'text': 'World'}]},
+        ]
+
+        result = pydantic_list_type.process_result_value(data, dialect)
+        assert len(result) == 2
+        assert all(isinstance(art, Artifact) for art in result)
+        assert result[0].artifact_id == '1'
+        assert result[1].artifact_id == '2'
+
+
+def test_create_task_model():
+    """Test dynamic task model creation."""
+
+    # Create a fresh base to avoid table conflicts
+    class TestBase(DeclarativeBase):
+        pass
+
+    # Create with default table name
+    default_task_model = create_task_model('test_tasks_1', TestBase)
+    assert default_task_model.__tablename__ == 'test_tasks_1'
+    assert default_task_model.__name__ == 'TaskModel_test_tasks_1'
+
+    # Create with custom table name
+    custom_task_model = create_task_model('test_tasks_2', TestBase)
+    assert custom_task_model.__tablename__ == 'test_tasks_2'
+    assert custom_task_model.__name__ == 'TaskModel_test_tasks_2'
+
+
+def test_create_push_notification_config_model():
+    """Test dynamic push notification config model creation."""
+
+    # Create a fresh base to avoid table conflicts
+    class TestBase(DeclarativeBase):
+        pass
+
+    # Create with default table name
+    default_model = create_push_notification_config_model(
+        'test_push_configs_1', TestBase
+    )
+    assert default_model.__tablename__ == 'test_push_configs_1'
+
+    # Create with custom table name
+    custom_model = create_push_notification_config_model(
+        'test_push_configs_2', TestBase
+    )
+    assert custom_model.__tablename__ == 'test_push_configs_2'
+    assert 'test_push_configs_2' in custom_model.__name__
diff --git a/tests/utils/test_constants.py b/tests/utils/test_constants.py
new file mode 100644
index 000000000..59e9b8366
--- /dev/null
+++ b/tests/utils/test_constants.py
@@ -0,0 +1,21 @@
+"""Tests for a2a.utils.constants module."""
+
+from a2a.utils import constants
+
+
+def test_agent_card_constants():
+    """Test that agent card constants have expected values."""
+    assert (
+        constants.AGENT_CARD_WELL_KNOWN_PATH == '/.well-known/agent-card.json'
+    )
+    assert (
+        constants.PREV_AGENT_CARD_WELL_KNOWN_PATH == '/.well-known/agent.json'
+    )
+    assert (
+        constants.EXTENDED_AGENT_CARD_PATH == '/agent/authenticatedExtendedCard'
+    )
+
+
+def test_default_rpc_url():
+    """Test default RPC URL constant."""
+    assert constants.DEFAULT_RPC_URL == '/'
diff --git a/tests/utils/test_error_handlers.py b/tests/utils/test_error_handlers.py
new file mode 100644
index 000000000..ec41dc1f5
--- /dev/null
+++ b/tests/utils/test_error_handlers.py
@@ -0,0 +1,92 @@
+"""Tests for a2a.utils.error_handlers module."""
+
+from unittest.mock import patch
+
+import pytest
+
+from a2a.types import (
+    InternalError,
+    InvalidRequestError,
+    MethodNotFoundError,
+    TaskNotFoundError,
+)
+from a2a.utils.error_handlers import (
+    A2AErrorToHttpStatus,
+    rest_error_handler,
+    rest_stream_error_handler,
+)
+from a2a.utils.errors import ServerError
+
+
+class MockJSONResponse:
+    def __init__(self, content, status_code):
+        self.content = content
+        self.status_code = status_code
+
+
+@pytest.mark.asyncio
+async def test_rest_error_handler_server_error():
+    """Test rest_error_handler with ServerError."""
+    error = InvalidRequestError(message='Bad request')
+
+    @rest_error_handler
+    async def failing_func():
+        raise ServerError(error=error)
+
+    with patch('a2a.utils.error_handlers.JSONResponse', MockJSONResponse):
+        result = await failing_func()
+
+    assert isinstance(result, MockJSONResponse)
+    assert result.status_code == 400
+    assert result.content == {'message': 'Bad request'}
+
+
+@pytest.mark.asyncio
+async def test_rest_error_handler_unknown_exception():
+    """Test rest_error_handler with unknown exception."""
+
+    @rest_error_handler
+    async def failing_func():
+        raise ValueError('Unexpected error')
+
+    with patch('a2a.utils.error_handlers.JSONResponse', MockJSONResponse):
+        result = await failing_func()
+
+    assert isinstance(result, MockJSONResponse)
+    assert result.status_code == 500
+    assert result.content == {'message': 'unknown exception'}
+
+
+@pytest.mark.asyncio
+async def test_rest_stream_error_handler_server_error():
+    """Test rest_stream_error_handler with ServerError."""
+    error = InternalError(message='Internal server error')
+
+    @rest_stream_error_handler
+    async def failing_stream():
+        raise ServerError(error=error)
+
+    with pytest.raises(ServerError) as exc_info:
+        await failing_stream()
+
+    assert exc_info.value.error == error
+
+
+@pytest.mark.asyncio
+async def test_rest_stream_error_handler_reraises_exception():
+    """Test rest_stream_error_handler reraises other exceptions."""
+
+    @rest_stream_error_handler
+    async def failing_stream():
+        raise RuntimeError('Stream failed')
+
+    with pytest.raises(RuntimeError, match='Stream failed'):
+        await failing_stream()
+
+
+def test_a2a_error_to_http_status_mapping():
+    """Test A2AErrorToHttpStatus mapping."""
+    assert A2AErrorToHttpStatus[InvalidRequestError] == 400
+    assert A2AErrorToHttpStatus[MethodNotFoundError] == 404
+    assert A2AErrorToHttpStatus[TaskNotFoundError] == 404
+    assert A2AErrorToHttpStatus[InternalError] == 500