1 files changed, 66 insertions, 0 deletions
diff --git a/tests/bot/rules/test_duplicates.py b/tests/bot/rules/test_duplicates.py
new file mode 100644
index 000000000..59e0fb6ef
--- /dev/null
+++ b/tests/bot/rules/test_duplicates.py
@@ -0,0 +1,66 @@
+from typing import Iterable
+
+from bot.rules import duplicates
+from tests.bot.rules import DisallowedCase, RuleTest
+from tests.helpers import MockMessage, async_test
+
+
+def make_msg(author: str, content: str) -> MockMessage:
+    """Give a MockMessage instance with `author` and `content` attrs."""
+    return MockMessage(author=author, content=content)
+
+
+class DuplicatesRuleTests(RuleTest):
+    """Tests the `duplicates` antispam rule."""
+
+    def setUp(self):
+        self.apply = duplicates.apply
+        self.config = {"max": 2, "interval": 10}
+
+    @async_test
+    async def test_allows_messages_within_limit(self):
+        """Cases which do not violate the rule."""
+        cases = (
+            [make_msg("alice", "A"), make_msg("alice", "A")],
+            [make_msg("alice", "A"), make_msg("alice", "B"), make_msg("alice", "C")],  # Non-duplicate
+            [make_msg("alice", "A"), make_msg("bob", "A"), make_msg("alice", "A")],  # Different author
+        )
+
+        await self.run_allowed(cases)
+
+    @async_test
+    async def test_disallows_messages_beyond_limit(self):
+        """Cases with too many duplicate messages from the same author."""
+        cases = (
+            DisallowedCase(
+                [make_msg("alice", "A"), make_msg("alice", "A"), make_msg("alice", "A")],
+                ("alice",),
+                3,
+            ),
+            DisallowedCase(
+                [make_msg("bob", "A"), make_msg("alice", "A"), make_msg("bob", "A"), make_msg("bob", "A")],
+                ("bob",),
+                3,  # 4 duplicate messages, but only 3 from bob
+            ),
+            DisallowedCase(
+                [make_msg("bob", "A"), make_msg("bob", "B"), make_msg("bob", "A"), make_msg("bob", "A")],
+                ("bob",),
+                3,  # 4 message from bob, but only 3 duplicates
+            ),
+        )
+
+        await self.run_disallowed(cases)
+
+    def relevant_messages(self, case: DisallowedCase) -> Iterable[MockMessage]:
+        last_message = case.recent_messages[0]
+        return tuple(
+            msg
+            for msg in case.recent_messages
+            if (
+                msg.author == last_message.author
+                and msg.content == last_message.content
+            )
+        )
+
+    def get_report(self, case: DisallowedCase) -> str:
+        return f"sent {case.n_violations} duplicated messages in {self.config['interval']}s"