Testing

A green build proves little: most addon bugs are silent. Check a positive signal (a recipe count, a log line, a test that asserts the value) and test on all six nodes.

Declaring GameTests

Golem Core’s dev.golem.core.gametest.GameTests declares tests once; they run on every loader.

public final class SpaceGameTests {

    public static final GameTests.Suite TESTS = GameTests.suite(NtmSpace.MOD_ID);

    public static final GameTests.Function FAN_SUBSTITUTION = TESTS.function("fan_substitution", 20,
            () -> SpaceGameTests::fanSubstitution);

    private static void fanSubstitution(GameTestHelper helper) {
        Block fan = ModMachineBlocks.fan.get();
        if (!(fan instanceof SpaceMachineFan)) {
            fail(helper, "hbm:fan is " + fan.getClass().getName() + ", not NTM: Space's substitute"); // its own helper
            return;
        }
        helper.succeed();
    }
}

Call	Does
`GameTests.suite(namespace)`	a suite; test ids are `<namespace>:<name>`
`suite.function(name, timeoutTicks, () -> body)`	declares a test; `body` is a `Consumer<GameTestHelper>`
`suite.function(name, timeoutTicks, padding, () -> body)`	the same with `padding` blocks of free space around its plot (for large structures)

Initialise the suite classes from declare().

A test whose entity leaves its plot (a rocket in flight) needs the chunks it moves through kept loaded: GameTests.holdChunks(helper, minX, maxX, minZ, maxZ) holds them, relative to the test’s origin, until the returned Runnable runs. GameTest ticks run back to back, so a test that waits for chunk generation must wait in real time, not only in ticks.

Registering per loader

NeoForge / Forge: from your @Mod constructor, bus.addListener((RegisterGameTestsEvent event) -> GameTests.register(event, TESTS)) (see Mod entry). The run also needs your namespace in neoforge.enabledGameTestNamespaces / forge.enabledGameTestNamespaces.
Fabric 26.1: Golem Core registers every declared suite itself.
Fabric below 26.1: a fabric-gametest entrypoint with a @GameTestGenerator that returns GameTests.functionsOf(TESTS):

public final class FabricGameTests {

    public FabricGameTests() {}

    //? if fabric && <26.1 {
    /*@net.minecraft.gametest.framework.GameTestGenerator
    public static java.util.Collection<net.minecraft.gametest.framework.TestFunction> generate() {
        com.ntmspace.gametest.SpaceGameTests.initAll();
        return dev.golem.core.gametest.GameTests.functionsOf(com.ntmspace.gametest.SpaceGameTests.TESTS);
    }
    *///?}
}

Running

./gradlew :26.1-neoforge:runGameTestServer                      # NeoForge and Forge
./gradlew :1.21.1-fabric:runGametest                            # Fabric
./gradlew :26.1-neoforge:runGameTestServer -Pgametest.filter="ntmspace:fan_.*"

-Pgametest.filter=<regex> is passed to the run as -Dgolem.gametest.filter and selects test ids by regular expression. NTM: Space’s default filter is (ntmspace|ntmprobe):.*, so its runs skip HBM’s own tests. Delete the run’s world folder before each run (NTM: Space’s buildscripts do this) so every run starts from an empty world.

GameTests are timing-sensitive under load. Re-run a failing test before blaming your change.

Building every node

./gradlew chiseledBuild           # builds all six nodes
./gradlew :26.1-neoforge:compileJava
./gradlew :26.1-neoforge:dejsonVerify
./gradlew "Reset active project"  # back to the vcsVersion node before committing

Stonecutter rewrites src/ in place for the active node, so only one node compiles at a time; chiseledBuild switches between them. Each node runs on its own Java (25, 21, 17). Only runClient catches model, texture and renderer faults, and only runServer (or a GameTest run) catches datapack and loot faults. After changing anything you can click (a menu, a block interaction), open it in game on each loader.

Scripted client checks

HBM and NTM: Space use a shared harness that drives real dev clients and takes screenshots: ../Golem-Core/harness/harness, configured by your project’s harness.json, with scenarios in harness/scenarios. See Golem-Core/harness/README.md in the Golem Core repository for setup.