Fix incorrect Select max option condition

discord/ui/select.py

@@ -499,7 +499,7 @@ class Select(BaseSelect[V]):
             The number of options exceeds 25.
         """
 
-        if len(self._underlying.options) > 25:
+        if len(self._underlying.options) >= 25:
             raise ValueError('maximum number of options already provided')
 
         self._underlying.options.append(option)

tests/test_ui_selects.py

@@ -0,0 +1,39 @@
+"""
+The MIT License (MIT)
+
+Copyright (c) 2015-present Rapptz
+
+Permission is hereby granted, free of charge, to any person obtaining a
+copy of this software and associated documentation files (the "Software"),
+to deal in the Software without restriction, including without limitation
+the rights to use, copy, modify, merge, publish, distribute, sublicense,
+and/or sell copies of the Software, and to permit persons to whom the
+Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
+"""
+
+from __future__ import annotations
+
+import discord
+import pytest
+
+
+@pytest.mark.asyncio
+async def test_add_option():
+    select = discord.ui.Select()
+
+    for i in range(1, 25 + 1):
+        select.add_option(label=str(i), value=str(i))
+
+    with pytest.raises(ValueError):
+        select.add_option(label="26", value="26")