> ## Documentation Index
> Fetch the complete documentation index at: https://docs.codecrafters.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Building your challenge

> Details on building the stage instructions and test cases for your challenge.

<Note>
  The CodeCrafters creators program is invite-only. Interested in building
  CodeCrafters challenges? Write to us at <b>[hello@codecrafters.io](mailto:hello@codecrafters.io)</b>.
</Note>

Once you've [pre-launched your challenge](/contributors/authoring-challenges/pre-launching-your-challenge), you're ready to start building out the
stage instructions and test cases.

It's upto you whether you want to build test cases first or stage instructions first. We recommend building both in parallel, one stage at a time. This allows
you to think about how a learner will progress through your challenge, and what they'll need at each stage.

## Test Cases

For each stage defined in your `course-definition.yml` file, you'll need a corresponding test case. These are defined in your tester repository. Here
are some examples from our other challenges:

* [Redis](https://github.com/codecrafters-io/redis-tester)
* [Docker](https://github.com/codecrafters-io/docker-tester)
* [Git](https://github.com/codecrafters-io/git-tester)

We recommend testing your test cases against a "reference" implementation. For example, in the Git challenge we test `git-tester` by running it against the official
`git` command.

## Stage Instructions

Stage instructions are present in the `course-definition.yml` file (under the `description_md` key). Here are some examples from our other challenges:

* [Redis](https://github.com/codecrafters-io/build-your-own-redis/blob/main/course-definition.yml)
* [Docker](https://github.com/codecrafters-io/build-your-own-docker/blob/main/course-definition.yml)
* [Git](https://github.com/codecrafters-io/build-your-own-git/blob/main/course-definition.yml)

***

Note: we're still building the external course authoring feature, so updates to your tester program might not be visible on `app.codecrafters.io` immediately. Updates to the stage
instructions should be visible immediately once they're "applied" from the admin area. Let Paul know if you run into any issues.