Add test verifying PUBSUB NUMPAT behavior (#9209)

(cherry picked from commit 8b8f05c86c1f1f002caa1f4e1877020389f167e4)

tests/unit/pubsub.tcl

@@ -152,6 +152,24 @@ start_server {tags {"pubsub network"}} {
         r pubsub numsub abc def
     } {abc 0 def 0}
 
+    test "NUMPATs returns the number of unique patterns" {
+        set rd1 [redis_deferring_client]
+        set rd2 [redis_deferring_client]
+
+        # Three unique patterns and one that overlaps
+        psubscribe $rd1 "foo*"
+        psubscribe $rd2 "foo*"
+        psubscribe $rd1 "bar*"
+        psubscribe $rd2 "baz*"
+
+        set patterns [r pubsub numpat]
+
+        # clean up clients
+        punsubscribe $rd1
+        punsubscribe $rd2
+        assert_equal 3 $patterns
+    }
+
     test "Mix SUBSCRIBE and PSUBSCRIBE" {
         set rd1 [redis_deferring_client]
         assert_equal {1} [subscribe $rd1 {foo.bar}]