tests: Add adapter-level tests for merels via game_handler.

Mirror the style used by connect_four to exercise the GameAdapter
flow for Merels. Use stable fragments to avoid brittleness.

Included:
- help shows Merels help
- start game posts an invite with “wants to play”, “Merels”, “join”
- join triggers start message (containment)
- light checks for MerelsMessageHandler helpers

No production changes; tests only.

Fixes #433.

Author: sulahmed20

zulip_bots/zulip_bots/bots/merels/test_merels_adapter.py

@@ -0,0 +1,103 @@
+from typing import Dict
+
+from typing_extensions import override
+
+from zulip_bots.test_lib import BotTestCase, DefaultTests
+
+
+class TestMerelsAdapter(BotTestCase, DefaultTests):
+    bot_name = "merels"
+
+    @override
+    def make_request_message(
+        self, content: str, user: str = "[email protected]", user_name: str = "foo"
+    ) -> Dict[str, str]:
+        # Include stream context; the adapter checks message["type"] and topic.
+        return {
+            "sender_email": user,
+            "sender_full_name": user_name,
+            "content": content,
+            "type": "stream",
+            "display_recipient": "general",
+            "subject": "merels-test-topic",
+        }
+
+    def test_help_is_merels_help(self) -> None:
+        bot, bot_handler = self._get_handlers()
+
+        bot_handler.reset_transcript()
+        bot.handle_message(self.make_request_message("help"), bot_handler)
+
+        responses = [m for (_method, m) in bot_handler.transcript]
+        self.assertTrue(responses, "No bot response to 'help'")
+        help_text = responses[0]["content"]
+
+        # Assert on stable fragments; avoid brittle exact-match checks.
+        self.assertIn("Merels Bot Help", help_text)
+        self.assertIn("start game", help_text)
+        self.assertIn("play game", help_text)
+        self.assertIn("quit", help_text)
+        self.assertIn("rules", help_text)
+        # Present today; OK to drop later if wording changes.
+        self.assertIn("leaderboard", help_text)
+        self.assertIn("cancel game", help_text)
+
+    def test_start_game_emits_invite(self) -> None:
+        bot, bot_handler = self._get_handlers()
+        bot_handler.reset_transcript()
+
+        bot.handle_message(
+            self.make_request_message("start game", user="[email protected]", user_name="foo"),
+            bot_handler,
+        )
+
+        responses = [m["content"] for (_method, m) in bot_handler.transcript]
+        self.assertTrue(responses, "No bot reply recorded for 'start game'")
+        first = responses[0]
+        self.assertIn("wants to play", first)
+        self.assertIn("Merels", first)
+        self.assertIn("join", first)
+
+    def test_join_starts_game_emits_start_message(self) -> None:
+        bot, bot_handler = self._get_handlers()
+        expected_fragment = bot.game_message_handler.game_start_message()
+
+        bot_handler.reset_transcript()
+        bot.handle_message(
+            self.make_request_message("start game", user="[email protected]", user_name="foo"),
+            bot_handler,
+        )
+        bot.handle_message(
+            self.make_request_message("join", user="[email protected]", user_name="bar"),
+            bot_handler,
+        )
+
+        contents = [m["content"] for (_method, m) in bot_handler.transcript]
+        self.assertTrue(
+            any(expected_fragment in c for c in contents),
+            "Merels start message not found after 'join'",
+        )
+
+    def test_message_handler_helpers(self) -> None:
+        bot, _ = self._get_handlers()
+
+        # parse_board is identity for Merels.
+        self.assertEqual(
+            bot.game_message_handler.parse_board("sample_board_repr"), "sample_board_repr"
+        )
+
+        # Token color is one of the known emoji.
+        self.assertIn(
+            bot.game_message_handler.get_player_color(0),
+            (":o_button:", ":cross_mark_button:"),
+        )
+        self.assertIn(
+            bot.game_message_handler.get_player_color(1),
+            (":o_button:", ":cross_mark_button:"),
+        )
+
+        # Basic move alert format.
+        self.assertEqual(
+            bot.game_message_handler.alert_move_message("foo", "move 1,1"),
+            "foo :move 1,1",
+        )