diff --git a/tests/server/test_id_generator.py b/tests/server/test_id_generator.py
new file mode 100644
index 00000000..3a842e6a
--- /dev/null
+++ b/tests/server/test_id_generator.py
@@ -0,0 +1,166 @@
+"""Tests for IDGenerator abstract base class."""
+
+import uuid
+
+from unittest.mock import patch
+
+import pytest
+
+from pydantic import ValidationError
+
+from a2a.server.id_generator import (
+    IDGenerator,
+    IDGeneratorContext,
+    UUIDGenerator,
+)
+
+
+class TestIDGeneratorContext:
+    """Tests for IDGeneratorContext."""
+
+    def test_context_creation_with_all_fields(self):
+        """Test creating context with all fields populated."""
+        context = IDGeneratorContext(
+            task_id='task_123', context_id='context_456'
+        )
+        assert context.task_id == 'task_123'
+        assert context.context_id == 'context_456'
+
+    def test_context_creation_with_defaults(self):
+        """Test creating context with default None values."""
+        context = IDGeneratorContext()
+        assert context.task_id is None
+        assert context.context_id is None
+
+    def test_context_creation_with_partial_fields(self):
+        """Test creating context with only some fields populated."""
+        context = IDGeneratorContext(task_id='task_123')
+        assert context.task_id == 'task_123'
+        assert context.context_id is None
+
+    def test_context_mutability(self):
+        """Test that context fields can be updated (Pydantic models are mutable by default)."""
+        context = IDGeneratorContext(task_id='task_123')
+        context.task_id = 'task_456'
+        assert context.task_id == 'task_456'
+
+    def test_context_validation(self):
+        """Test that context raises validation error for invalid types."""
+        with pytest.raises(ValidationError):
+            IDGeneratorContext(task_id={'not': 'a string'})  # noqa
+
+
+class TestIDGenerator:
+    """Tests for IDGenerator abstract base class."""
+
+    def test_cannot_instantiate_abstract_class(self):
+        """Test that IDGenerator cannot be instantiated directly."""
+        with pytest.raises(TypeError):
+            IDGenerator()
+
+    def test_subclass_must_implement_generate(self):
+        """Test that subclasses must implement the generate method."""
+
+        class IncompleteGenerator(IDGenerator):
+            pass
+
+        with pytest.raises(TypeError):
+            IncompleteGenerator()
+
+    def test_valid_subclass_implementation(self):
+        """Test that a valid subclass can be instantiated."""
+
+        class ValidGenerator(IDGenerator):  # pylint: disable=C0115,R0903
+            def generate(self, context: IDGeneratorContext) -> str:
+                return 'test_id'
+
+        generator = ValidGenerator()
+        assert generator.generate(IDGeneratorContext()) == 'test_id'
+
+
+class TestUUIDGenerator:
+    """Tests for UUIDGenerator implementation."""
+
+    def test_generate_returns_string(self):
+        """Test that generate returns a string."""
+        generator = UUIDGenerator()
+        context = IDGeneratorContext()
+        result = generator.generate(context)
+        assert isinstance(result, str)
+
+    def test_generate_returns_valid_uuid(self):
+        """Test that generate returns a valid UUID format."""
+        generator = UUIDGenerator()
+        context = IDGeneratorContext()
+        result = generator.generate(context)
+        uuid.UUID(result)
+
+    def test_generate_returns_uuid_version_4(self):
+        """Test that generate returns a UUID version 4."""
+        generator = UUIDGenerator()
+        context = IDGeneratorContext()
+        result = generator.generate(context)
+        parsed_uuid = uuid.UUID(result)
+        assert parsed_uuid.version == 4
+
+    def test_generate_ignores_context(self):
+        """Test that generate ignores the context parameter."""
+        generator = UUIDGenerator()
+        context1 = IDGeneratorContext(task_id='task_1', context_id='context_1')
+        context2 = IDGeneratorContext(task_id='task_2', context_id='context_2')
+        result1 = generator.generate(context1)
+        result2 = generator.generate(context2)
+        uuid.UUID(result1)
+        uuid.UUID(result2)
+        assert result1 != result2
+
+    def test_generate_produces_unique_ids(self):
+        """Test that multiple calls produce unique IDs."""
+        generator = UUIDGenerator()
+        context = IDGeneratorContext()
+        ids = [generator.generate(context) for _ in range(100)]
+        # All IDs should be unique
+        assert len(ids) == len(set(ids))
+
+    def test_generate_with_empty_context(self):
+        """Test that generate works with an empty context."""
+        generator = UUIDGenerator()
+        context = IDGeneratorContext()
+        result = generator.generate(context)
+        assert isinstance(result, str)
+        uuid.UUID(result)
+
+    def test_generate_with_populated_context(self):
+        """Test that generate works with a populated context."""
+        generator = UUIDGenerator()
+        context = IDGeneratorContext(
+            task_id='task_123', context_id='context_456'
+        )
+        result = generator.generate(context)
+        assert isinstance(result, str)
+        uuid.UUID(result)
+
+    @patch('uuid.uuid4')
+    def test_generate_calls_uuid4(self, mock_uuid4):
+        """Test that generate uses uuid.uuid4() internally."""
+        mock_uuid = uuid.UUID('12345678-1234-5678-1234-567812345678')
+        mock_uuid4.return_value = mock_uuid
+        generator = UUIDGenerator()
+        context = IDGeneratorContext()
+        result = generator.generate(context)
+        mock_uuid4.assert_called_once()
+        assert result == str(mock_uuid)
+
+    def test_generator_is_instance_of_id_generator(self):
+        """Test that UUIDGenerator is an instance of IDGenerator."""
+        generator = UUIDGenerator()
+        assert isinstance(generator, IDGenerator)
+
+    def test_multiple_generators_produce_different_ids(self):
+        """Test that multiple generator instances produce different IDs."""
+        generator1 = UUIDGenerator()
+        generator2 = UUIDGenerator()
+        context = IDGeneratorContext()
+        result1 = generator1.generate(context)
+        result2 = generator2.generate(context)
+        assert result1 != result2