diff --git a/tests/test_main.py b/tests/test_main.py
index 8062df0..b2a55d0 100644
--- a/tests/test_main.py
+++ b/tests/test_main.py
@@ -1,3 +1,7 @@
+import pickle
+
+from typing_extensions import Annotated, get_type_hints
+
 from annotated_doc import Doc
 
 
@@ -9,3 +13,41 @@ def test_doc_basic() -> None:
     assert doc == Doc("This is a test documentation.")
     assert doc != Doc("Different documentation.")
     assert doc != "Not a Doc instance"
+
+
+def test_annotation():
+    def hi(name: Annotated[str, Doc("Who to say hi to")]) -> None:  # pragma: no cover
+        pass
+
+    hints = get_type_hints(hi, include_extras=True)
+    doc_info: Doc = hints["name"].__metadata__[0]
+    assert doc_info.documentation == "Who to say hi to"
+    assert isinstance(doc_info, Doc)
+
+
+def test_repr():
+    doc_info = Doc("Who to say hi to")
+    assert repr(doc_info) == "Doc('Who to say hi to')"
+
+
+def test_hashability():
+    doc_info = Doc("Who to say hi to")
+    assert isinstance(hash(doc_info), int)
+    assert hash(doc_info) != hash(Doc("Who not to say hi to"))
+
+
+def test_equality():
+    doc_info = Doc("Who to say hi to")
+    # Equal to itself
+    assert doc_info == doc_info
+    # Equal to another instance with the same string
+    assert doc_info == Doc("Who to say hi to")
+    # Not equal to another instance with a different string
+    assert doc_info != Doc("Who not to say hi to")
+
+
+def test_pickle():
+    doc_info = Doc("Who to say hi to")
+    for proto in range(pickle.HIGHEST_PROTOCOL + 1):
+        pickled = pickle.dumps(doc_info, protocol=proto)
+        assert doc_info == pickle.loads(pickled)