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k3s/docs/adrs/testing-2024.md

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# Testing in K3s
Date: 2024-02-23
# Context
## Background
Currently, Testing in K3s is categorized into various types and spread across Github Actions and Drone CI. The types are as follows:
GitHub Actions:
- Unit Tests: For testing individual components and functions, following a "white box" approach.
- Integration Tests: Test functionalities across multiple packages, using "black box" testing.
- Smoke Tests: Simple tests to ensure basic functionality works as expected. Broken into:
- Cgroup: Tests cgroupv2 support.
- Snapshotter: tests btrfs and overlayfs snapshotter support.
- Install tests: Tests the installation of K3s on various OSes.
Drone CI:
- Docker Tests: Run clusters in containers to test basic functionality. Broken into:
- Basic Tests: Run clusters in containers to test basic functionality.
- Sonobuoy Conformance Tests: Run clusters in containers to validate K8s conformance. Runs on multiple database backends.
- End-to-End (E2E) Tests: Cover multi-node configuration/administration.
- Performance Tests: Use Terraform to test large-scale deployments of K3s clusters. These were legacy tests and are never run in CI.
## Problems
- The current testing infrastructure is complex and fragmented, leading to maintenance overhead. Not all testing is grouped inside the [tests directory](../../tests/).
- GitHub Actions had limited resources, making it unsuitable for running larger tests.
- GitHub Actions only supported hardware virtualiztion on Mac runners and that support was often broken.
- Drone CI cannot handle individual testing failures. If a single test fails, the entire build is marked as failed.
## New Developments
As of late January 2024, GitHub Actions has made significant improvements:
- The resources available to open source GitHub Actions have been doubled, with 4 CPU cores and 16GB of RAM. See blog post [here](https://github.blog/2024-01-17-github-hosted-runners-double-the-power-for-open-source/).
- Standard (i.e. free) Linux runners now support Nested Virtualization
## Decision
We will move towards a single testing platform, GitHub Actions, and leverage the recent improvements in resources and nested virtualization support. This will involve the following changes:
- Test distribution based on size and complexity:
- Unit, Integration: Will continue to run in GitHub Actions due to their smaller scale and faster execution times.
- Install Test, Docker Basic, and E2E Tests: Will run in GitHub Actions on standard linux runners thanks to recent enhancements.
- Docker Conformance and large E2E Tests (2+ nodes): Still utilize Drone CI for resource-intensive scenarios.
- Consolidating all testing-related files within the "tests" directory for better organization and clarity.
- Cgroup smoke tests will be removed. As multiple Operating Systems now support CgroupV2 by default, these tests are no longer relevant.
- Snapshotter smoke test will be converted into a full E2E test.
- Remove of old performance tests, as they are no longer relevant. Scale testing is already handled by QA as needed.
Tracking these changes is with [this issue](https://github.com/k3s-io/k3s/issues/9477)
## Consequences
- The testing infrastructure will be more organized and easier to maintain.
- The move to GitHub Actions will allow for faster feedback on PRs and issues.
- The removal of old tests will reduce the maintenance overhead.
- New testing process can be used as a model for related projects.