@Experimental package net.fabricmc.fabric.api.client.gametest.v1

Provides support for client gametests. To register a client gametest, add an entry to the fabric-client-gametest entrypoint in your fabric.mod.json. Your gametest class should implement FabricClientGameTest.

Lifecycle

Client gametests are run sequentially. When a gametest ends, the game will be returned to the title screen. When all gametests have been run, the game will be closed.

Threading

Client gametests run on the client gametest thread. Use the functions inside ClientGameTestContext and other test helper classes to run code on the correct thread. Exceptions are transparently rethrown on the test thread, and their stack traces are mutated to include the async stack trace, to make them easy to track. You can disable this behavior by setting the fabric.client.gametest.disableJoinAsyncStackTraces system property.

The game remains paused unless you explicitly unpause it using various waiting functions such as ClientGameTestContext.waitTick().

A few changes have been made to how the vanilla game threads run, to make tests more reproducible. Notably, there is exactly one server tick per client tick while a server is running (singleplayer or multiplayer). On singleplayer, packets will always arrive on a consistent tick.

Default settings

The client gametest API adjusts some default settings, usually for consistency of tests. These settings can always be changed back to the default value or a different value inside a gametest.

Game options

Setting name	Gametest default	Vanilla default	Reason
Tutorial step	`NONE`	`MOVEMENT`	Consistency of tests
Cloud render mode	`OFF`	`FANCY`	Consistency of tests
Onboard accessibility	`false`	`true`	Would cause the game test runner to have to click through the onboard accessibility prompt
View distance	`5`	`10`	Speeds up loading of chunks, especially for functions such as `TestClientWorldContext.waitForChunksRender()`
Music volume	`0.0`	`1.0`	The game music is annoying while running gametests

World creation options

These adjusted defaults only apply if the world builder's consistent settings have not been set to false.

Setting name	Gametest default	Vanilla default	Reason
World type	`FLAT`	`DEFAULT`	Creates cleaner test cases
Seed	`1`	Random value	Consistency of tests
Generate structures	`false`	`true`	Consistency of tests and creates cleaner tests
Do daylight cycle	`false`	`true`	Consistency of tests
Do weather cycle	`false`	`true`	Consistency of tests
Do mob spawning	`false`	`true`	Consistency of tests

Dedicated server properties

Setting name	Gametest default	Vanilla default	Reason
`online-mode`	`false`	`true`	Allows the gametest client to connect to the dedicated server without being logged in to a Minecraft account
`sync-chunk-writes`	`true` on Windows, `false` on other operating systems	`true`	Causes world saving and closing to be extremely slow (on the order of many seconds to minutes) on Unix systems. The vanilla default is set correctly in singleplayer but not on dedicated servers.
`spawn-protection`	`0`	`16`	Spawn protection prevents non-opped players from modifying the world within a certain radius of the world spawn point, a likely source of confusion when writing gametests
`max-players`	`1`	`20`	Stops other players from joining the server and interfering with the test