test_buttons: Add test for PMButton button text.

tests/ui_tools/test_buttons.py

@@ -1,3 +1,4 @@
+import re
 from typing import Any, Callable, Dict, List, Optional, Tuple, Union
 
 import pytest
@@ -13,6 +14,7 @@
     EmojiButton,
     MessageLinkButton,
     ParsedNarrowLink,
+    PMButton,
     StarredButton,
     StreamButton,
     TopButton,
@@ -178,6 +180,17 @@ def test_update_widget(
         set_attr_map.assert_called_once_with({None: top_button.label_style})
 
 
+class TestPMButton:
+    def test_button_text(self, mocker: MockerFixture, count: int = 10) -> None:
+        pm_button = PMButton(controller=mocker.Mock(), count=count)
+        title_text = pm_button.label_text[:-3].strip()
+        hotkey_text = pm_button.label_text[-3:]
+        # regex checks fixed length = 20, title capitalization, and presence of hotkey
+        pattern = re.compile(r"(?=.{20}$)[A-Z].{1,15}[ ]{1,16}\[.\]")
+        assert pattern.match(pm_button.label_text), "Button text does not match regex"
+        assert title_text == "Direct messages" and hotkey_text == "[P]"
+
+
 class TestStarredButton:
     def test_count_style_init_argument_value(
         self, mocker: MockerFixture, count: int = 10