GameTests

MCTest can run Minecraft's GameTests in the open world and report each result, so an agent can write a GameTest, rebuild, and check it in one loop.

Tool	What it does
mc_gametest_list {filter?}	GameTests registered in the singleplayer world: vanilla, your mod's, and datapack test instances
mc_gametest_run {tests?, timeoutSeconds?}	Run tests (/test run <selector>) and wait. Returns pass/fail per test with the failure message and position, plus an overall success

mc_world_create {name:"gt", flat:true}
→ mc_gametest_run {tests:"mymod:*"}

• Register tests through the Fabric or NeoForge GameTest API, or as test_instance JSON in a datapack.
• Use a flat test world: tests are placed near the world spawn.
• A world whose datapacks add registry content shows the "experimental settings / backup" prompt on load. mc_world_join answers it for you unless you pass confirmPrompts: false.
• The same tools exist on a dedicated server as mc_server_gametest_list and mc_server_gametest_run. See Dedicated servers.