feat: launch a Minecraft client in CI to verify the mod works in-game

[dsnsgithub]

Summary

CI now verifies the mod in a real running game. On every push, the workflow builds the jar, boots a production Fabric client (Minecraft 26.2 + Fabric Loader with Fabric API, Mod Menu, and Cloth Config as real mod jars) under a virtual display, generates and enters a survival singleplayer world with the HUD active, and fails the build if the game crashes anywhere along the way. The in-world screenshot is posted on the pull request as a quick visual sanity check.

Key Changes

• CI workflow (.github/workflows/build.yml)
  • Installs Xvfb and runs the new runProductionClientGameTest Gradle task after the build
  • Posts (and keeps updated) a single PR comment embedding the in-world screenshot; images are stored per commit on the ci-screenshots branch so older comments keep rendering
  • Uploads game logs and screenshots as a client-launch-test artifact, including on failure, for easy crash diagnosis
  • Adds workflow-level contents: write / pull-requests: write permissions for the screenshot step, and renames all steps to consistent title case
• Build configuration (build.gradle)
  • Registers runProductionClientGameTest (Loom ClientProductionRunTask), which launches a production client with the built mod jar, the dependency mods from the new productionRuntimeMods configuration, and the gametest mod; on Linux CI Loom runs it under Xvfb automatically
  • Wires a gametest source set via fabricApi.configureTests and packages it as gametestJar
• Client gametest (src/gametest/)
  • Screenshots the title screen, creates a survival-mode singleplayer world, waits for chunks to render, lets the world tick with the HUD rendering, and screenshots it
  • Asserts both screenshot PNGs actually exist and are non-empty, so a green build guarantees the captures were taken
• Dependencies (gradle.properties)
  • Mod Menu 18.0.0-alpha.8 → 20.0.0-alpha.1 and Cloth Config 26.1.154 → 26.2.155: the launch test caught that the older Mod Menu versions crash Minecraft 26.2 at the title screen (NoSuchMethodError: I18n.exists in its TitleScreen mixin)

Notes

• The test world uses the gametest framework's default flat terrain for speed and determinism; survival game mode is confirmed by the health/hunger bars in the capture
• Rendering on CI uses Mesa's software OpenGL under Xvfb; audio, narrator, and Realms warnings in the logs are expected in that headless environment and are non-fatal
• With warm Gradle caches the launch test adds roughly a minute to the workflow

🤖 Generated with Claude Code

https://claude.ai/code/session_01HqYsmitMrdZZBkd7zHTgYA

[github-actions]

Client launch test

The game launched and entered a survival singleplayer world on efad29b: