Add a test for RuntimeErrors.

This just tests that the various RuntimeErrors are reachable - that
includes the error about not having a bot instance, the one about not
being a class attribute, and the one about not having instantiated the
class.

This test addresses a concern raised by @MarkKoz in a review.

I've decided not to test that actual contents of these RuntimeErrors,
because I believe that sort of testing is a bit too brittle. It
shouldn't break a test just to change the content of an error string.

1 files changed, 22 insertions, 0 deletions

diff --git a/tests/bot/utils/test_redis_cache.py b/tests/bot/utils/test_redis_cache.py
index 7405487ed..1b05ae350 100644
--- a/tests/bot/utils/test_redis_cache.py
+++ b/tests/bot/utils/test_redis_cache.py
@@ -215,3 +215,25 @@ class RedisCacheTests(unittest.IsolatedAsyncioTestCase):
         await self.redis.set("stringthing", "stringthing")
         with self.assertRaises(TypeError):
             await self.redis.increment("stringthing")
+
+    async def test_exceptions_raised(self):
+        """Testing that the various RuntimeErrors are reachable."""
+        class MyCog:
+            cache = RedisCache()
+
+            def __init__(self):
+                self.other_cache = RedisCache()
+
+        cog = MyCog()
+
+        # Raises "No Bot instance"
+        with self.assertRaises(RuntimeError):
+            await cog.cache.get("john")
+
+        # Raises "RedisCache has no namespace"
+        with self.assertRaises(RuntimeError):
+            await cog.other_cache.get("was")
+
+        # Raises "You must access the RedisCache instance through the cog instance"
+        with self.assertRaises(RuntimeError):
+            await MyCog.cache.get("afraid")