api(deltachat-rpc-client): add Message.exists()

deltachat-rpc-client/tests/test_something.py

@@ -993,3 +993,22 @@ def test_background_fetch(acfactory, dc):
         snapshot = messages[-1].get_snapshot()
         if snapshot.text == "Hello again!":
             break
+
+
+def test_message_exists(acfactory):
+    ac1, ac2 = acfactory.get_online_accounts(2)
+    chat = ac1.create_chat(ac2)
+    message1 = chat.send_text("Hello!")
+    message2 = chat.send_text("Hello again!")
+    assert message1.exists()
+    assert message2.exists()
+
+    ac1.delete_messages([message1])
+    assert not message1.exists()
+    assert message2.exists()
+
+    # There is no error when checking if
+    # the message exists for deleted account.
+    ac1.remove()
+    assert not message1.exists()
+    assert not message2.exists()