> For the complete documentation index, see [llms.txt](https://docs.redefine.dev/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.redefine.dev/configuration/selection-modes.md).

# Selection Modes

Redefine offers four selection modes to optimize testing:

1. [Discover](/configuration/selection-modes/discover.md) mode collects data for improved predictions.
2. [Optimize](/configuration/selection-modes/optimize.md) mode runs relevant tests within a time budget.
3. [Fail-Fast](/configuration/selection-modes/fail-fast.md) mode stops CI runs if tests fail within the budget, or runs all tests if they pass.
4. [Prioritize](/configuration/selection-modes/prioritize.md) mode reorders tests for faster feedback, especially when integrated with Redefine Slack or a first-fail testing framework.

{% hint style="info" %}
To enhance your developer experience, we strongly recommend the use of [AI Slack Notifications](/integrations/ai-slack-notifications.md).
{% endhint %}