Add support for the DISCARD command in course-definition.yml

course-definition.yml

@@ -3576,7 +3576,30 @@ stages:
     name: "The DISCARD command"
     difficulty: easy
     description_md: |
-      **🚧 We're still working on instructions for this stage**. You can find notes on how the tester works below.
+      In this stage, you'll add support for the DISCARD command.
+
+      ### The DISCARD command
+
+      [DISCARD](https://redis.io/docs/latest/commands/discard/) is used to abort a transactions. It discards all commands queued in a transaction,
+      and returns `+OK\r\n`.
+
+      Example:
+
+      ```bash
+      $ redis-cli
+      > MULTI
+      OK
+      > SET foo 41
+      QUEUED
+      > DISCARD
+      OK
+      > DISCARD
+      (error) ERR DISCARD without MULTI
+      ```
+
+      In the above example, note that the first `DISCARD` returns `OK`, but the second `DISCARD` returns an error since the transaction was aborted.
+
+      ### DISCARD
 
       ### Tests
 
@@ -3589,13 +3612,13 @@ stages:
       The tester will then connect to your server as a Redis client, and send multiple commands using the same connection:
 
       ```bash
-      $ redis-cli MULTI
-      > SET foo 41
-      > INCR foo
-      > DISCARD
-      > GET foo
-      > GET bar
-      > DISCARD
+      $ redis-cli
+      > MULTI
+      > SET foo 41 (expecting "+QUEUED\r\n")
+      > INCR foo (expecting "+QUEUED\r\n")
+      > DISCARD (expecting "+OK\r\n")
+      > GET foo (expecting "$-1\r\n" as the response)
+      > DISCARD (expecting "-ERR DISCARD without MULTI\r\n" as the response)
       ```
 
     marketing_md: |