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Stage instructions are the heart of a CodeCrafters challenge. Remember that most learners will be new to both the CodeCrafters platform and your challenge itself, so it’s important to write clear, concise and helpful stage instructions.

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Structure

We recommend following this structure when writing stage instructions:
  1. Hook: A short sentence that describes what the user will do in this stage.
  2. Explanation: A longer explanation of the concepts involved in this stage, and what the user needs to implement.
  3. Tests: A clear description of how the user’s program will be tested, and what the expected output/behaviour is.
  4. Notes (optional): Any additional notes or tips that might be helpful for the user.

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Example

Here’s an example from the Redis challenge:
In this stage, you’ll add support for the TYPE command.

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The TYPE command

The TYPE command returns the type of value stored at a given key. It returns one of the following types: string, list, set, zset, hash, and stream. Here’s how it works: 
$ redis-cli set some_key foo
"OK"
$ redis-cli type some_key
"string"
If a key doesn’t exist, the return value will be “none”. 
$ redis-cli type missing_key
"none"
The return value is encoded as a simple string.

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Tests

The tester will execute your program like this: 
$ ./spawn_redis_server.sh
It’ll then send a SET command to your server. 
$ redis-cli set some_key foo
It’ll then send a TYPE command to your server. 
$ redis-cli type some_key
Your server should respond with +string\r\n, which is string encoded as a RESP simple string. It’ll then send another TYPE command with a missing key. 
$ redis-cli type missing_key
Your server should respond with +none\r\n, which is none encoded as a RESP simple string.

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Notes

  • For now, you only need to handle the “string” and “none” types. We’ll add support for the “stream” type in the next stage.