core[patch]: Add unit tests for Serializable (#25152)

Add a few test cases for serializable (many other test cases already
covered
throguh runnable tests).

libs/core/tests/unit_tests/load/test_serializable.py

@@ -0,0 +1,71 @@
+from typing import Dict
+
+from langchain_core.load import Serializable, dumpd
+
+
+def test_simple_serialization() -> None:
+    class Foo(Serializable):
+        bar: int
+        baz: str
+
+    foo = Foo(bar=1, baz="hello")
+    assert dumpd(foo) == {
+        "id": ["tests", "unit_tests", "load", "test_serializable", "Foo"],
+        "lc": 1,
+        "repr": "Foo(bar=1, baz='hello')",
+        "type": "not_implemented",
+    }
+
+
+def test_simple_serialization_is_serializable() -> None:
+    class Foo(Serializable):
+        bar: int
+        baz: str
+
+        @classmethod
+        def is_lc_serializable(cls) -> bool:
+            return True
+
+    foo = Foo(bar=1, baz="hello")
+    assert foo.lc_id() == ["tests", "unit_tests", "load", "test_serializable", "Foo"]
+    assert dumpd(foo) == {
+        "id": ["tests", "unit_tests", "load", "test_serializable", "Foo"],
+        "kwargs": {"bar": 1, "baz": "hello"},
+        "lc": 1,
+        "type": "constructor",
+    }
+
+
+def test_simple_serialization_secret() -> None:
+    """Test handling of secrets."""
+    from langchain_core.load import Serializable
+    from langchain_core.pydantic_v1 import SecretStr
+
+    class Foo(Serializable):
+        bar: int
+        baz: str
+        secret: SecretStr
+        secret_2: str
+
+        @classmethod
+        def is_lc_serializable(cls) -> bool:
+            return True
+
+        @property
+        def lc_secrets(self) -> Dict[str, str]:
+            return {"secret": "MASKED_SECRET", "secret_2": "MASKED_SECRET_2"}
+
+    foo = Foo(
+        bar=1, baz="baz", secret=SecretStr("SUPER_SECRET"), secret_2="SUPER_SECRET"
+    )
+    assert dumpd(foo) == {
+        "id": ["tests", "unit_tests", "load", "test_serializable", "Foo"],
+        "kwargs": {
+            "bar": 1,
+            "baz": "baz",
+            "secret": {"id": ["MASKED_SECRET"], "lc": 1, "type": "secret"},
+            "secret_2": {"id": ["MASKED_SECRET_2"], "lc": 1, "type": "secret"},
+        },
+        "lc": 1,
+        "type": "constructor",
+    }