test(frozen_dataclass): add example tests for sealable dataclass functionality

Author: tony

tests/examples/_internal/frozen_dataclass_sealable/test_basic.py

@@ -0,0 +1,94 @@
+#!/usr/bin/env python3
+"""Basic examples of frozen_dataclass_sealable usage.
+
+This file contains examples extracted from the docstring of the
+frozen_dataclass_sealable decorator, to demonstrate its functionality with
+working code examples.
+"""
+
+import pytest
+
+from dataclasses import dataclass, field
+from typing import Optional
+
+from libtmux._internal.frozen_dataclass_sealable import (
+    frozen_dataclass_sealable,
+    is_sealable,
+)
+
+
+def test_basic_usage():
+    """Test basic usage of frozen_dataclass_sealable."""
+    @frozen_dataclass_sealable
+    class Config:
+        name: str
+
+        values: dict[str, int] = field(
+            default_factory=dict,
+            metadata={"mutable_during_init": True}
+        )
+
+    # Create an instance
+    config = Config(name="test-config")
+    assert config.name == "test-config"
+    
+    # Cannot modify immutable fields
+    with pytest.raises(AttributeError):
+        config.name = "modified"
+    
+    # Can modify mutable fields
+    config.values["key1"] = 100
+    assert config.values["key1"] == 100
+
+    # Check sealable property
+    assert is_sealable(config)
+    
+    # Seal the object
+    config.seal()
+    assert hasattr(config, "_sealed") and config._sealed
+    
+    # Can still modify contents of mutable containers after sealing
+    config.values["key2"] = 200
+    assert config.values["key2"] == 200
+
+
+def test_deferred_sealing():
+    """Test deferred sealing with linked nodes."""
+    @frozen_dataclass_sealable
+    class Node:
+        value: int
+
+        next_node: Optional['Node'] = field(
+            default=None,
+            metadata={"mutable_during_init": True}
+        )
+
+    # Create a linked list (not circular to avoid recursion issues)
+    node1 = Node(value=1)
+    node2 = Node(value=2)
+    node1.next_node = node2
+    
+    # Verify structure
+    assert node1.value == 1
+    assert node2.value == 2
+    assert node1.next_node is node2
+    
+    # Verify sealable property
+    assert is_sealable(node1)
+    assert is_sealable(node2)
+    
+    # Seal nodes individually 
+    node1.seal()
+    node2.seal()
+    
+    # Verify both nodes are sealed
+    assert hasattr(node1, "_sealed") and node1._sealed
+    assert hasattr(node2, "_sealed") and node2._sealed
+    
+    # Verify immutability after sealing
+    with pytest.raises(AttributeError):
+        node1.value = 10
+
+
+if __name__ == "__main__":
+    pytest.main(["-xvs", __file__])