Wait for computers to run each tick in gametests

projects/common/src/testMod/java/dan200/computercraft/mixin/gametest/GameTestServerMixin.java

@@ -0,0 +1,51 @@
+// SPDX-FileCopyrightText: 2025 The CC: Tweaked Developers
+//
+// SPDX-License-Identifier: MPL-2.0
+
+package dan200.computercraft.mixin.gametest;
+
+import com.mojang.datafixers.DataFixer;
+import dan200.computercraft.gametest.core.TestHooks;
+import net.minecraft.gametest.framework.GameTestServer;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.Services;
+import net.minecraft.server.WorldStem;
+import net.minecraft.server.level.progress.ChunkProgressListenerFactory;
+import net.minecraft.server.packs.repository.PackRepository;
+import net.minecraft.world.level.storage.LevelStorageSource;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Overwrite;
+import org.spongepowered.asm.mixin.Shadow;
+
+import java.net.Proxy;
+import java.util.concurrent.locks.LockSupport;
+
+@Mixin(GameTestServer.class)
+abstract class GameTestServerMixin extends MinecraftServer {
+    GameTestServerMixin(Thread serverThread, LevelStorageSource.LevelStorageAccess storageSource, PackRepository packRepository, WorldStem worldStem, Proxy proxy, DataFixer fixerUpper, Services services, ChunkProgressListenerFactory progressListenerFactory) {
+        super(serverThread, storageSource, packRepository, worldStem, proxy, fixerUpper, services, progressListenerFactory);
+    }
+
+    /**
+     * Overwrite {@link GameTestServer#waitUntilNextTick()} to wait for all computers to finish executing.
+     * <p>
+     * This is a little dangerous (breaks async behaviour of computers), but it forces tests to be deterministic.
+     *
+     * @reason See above. This is only in the test mod, so no risk of collision.
+     * @author SquidDev.
+     */
+    @Overwrite
+    @Override
+    public void waitUntilNextTick() {
+        while (true) {
+            runAllTasks();
+            if (!haveTestsStarted() || TestHooks.areComputersIdle(this)) break;
+            LockSupport.parkNanos(100_000);
+        }
+    }
+
+    @Shadow
+    private boolean haveTestsStarted() {
+        throw new AssertionError("Stub.");
+    }
+}

projects/common/src/testMod/kotlin/dan200/computercraft/gametest/core/TestHooks.kt

@@ -5,6 +5,8 @@
 package dan200.computercraft.gametest.core
 
 import dan200.computercraft.api.ComputerCraftAPI
+import dan200.computercraft.core.ComputerContext
+import dan200.computercraft.core.computer.computerthread.ComputerThread
 import dan200.computercraft.gametest.*
 import dan200.computercraft.gametest.api.ClientGameTest
 import dan200.computercraft.gametest.api.TestTags
@@ -23,6 +25,8 @@ import net.minecraft.world.phys.Vec3
 import org.slf4j.Logger
 import org.slf4j.LoggerFactory
 import java.io.File
+import java.lang.invoke.MethodHandle
+import java.lang.invoke.MethodHandles
 import java.lang.reflect.InvocationTargetException
 import java.lang.reflect.Method
 import java.lang.reflect.Modifier
@@ -80,6 +84,9 @@ object TestHooks {
         CCTestCommand.importFiles(server)
     }
 
+    @JvmStatic
+    fun areComputersIdle(server: MinecraftServer) = ComputerThreadReflection.isFullyIdle(ServerContext.get(server))
+
     private val testClasses = listOf(
         Computer_Test::class.java,
         CraftOs_Test::class.java,
@@ -116,14 +123,6 @@ object TestHooks {
         }
     }
 
-    private val isCi = System.getenv("CI") != null
-
-    /**
-     * Adjust the timeout of a test. This makes it 1.5 times longer when run under CI, as CI servers are less powerful
-     * than our own.
-     */
-    private fun adjustTimeout(timeout: Int): Int = if (isCi) timeout + (timeout / 2) else timeout
-
     private fun registerTest(testClass: Class<*>, method: Method, fallbackRegister: Consumer<Method>) {
         val className = testClass.simpleName.lowercase()
         val testName = className + "." + method.name.lowercase()
@@ -135,7 +134,7 @@ object TestHooks {
                 TestFunction(
                     testInfo.batch, testName, testInfo.template.ifEmpty { testName },
                     StructureUtils.getRotationForRotationSteps(testInfo.rotationSteps),
-                    adjustTimeout(testInfo.timeoutTicks),
+                    testInfo.timeoutTicks,
                     testInfo.setupTicks,
                     testInfo.required, testInfo.requiredSuccesses, testInfo.attempts,
                 ) { value -> safeInvoke(method, value) },
@@ -149,10 +148,8 @@ object TestHooks {
 
             GameTestRegistry.getAllTestFunctions().add(
                 TestFunction(
-                    testName,
-                    testName,
-                    testInfo.template.ifEmpty { testName },
-                    adjustTimeout(testInfo.timeoutTicks),
+                    testName, testName, testInfo.template.ifEmpty { testName },
+                    testInfo.timeoutTicks,
                     0,
                     true,
                 ) { value -> safeInvoke(method, value) },
@@ -200,3 +197,31 @@ object TestHooks {
         return false
     }
 }
+
+/**
+ * Nasty reflection to determine if computers are fully idle.
+ *
+ * This is horribly nasty, and should not be used as a model for any production code!
+ *
+ * @see [ComputerThread.isFullyIdle]
+ * @see [dan200.computercraft.mixin.gametest.GameTestServerMixin]
+ */
+private object ComputerThreadReflection {
+    private val lookup = MethodHandles.lookup()
+
+    @JvmField
+    val computerContext: MethodHandle = lookup.unreflectGetter(
+        ServerContext::class.java.getDeclaredField("context").also { it.isAccessible = true },
+    )
+
+    @JvmField
+    val isFullyIdle: MethodHandle = lookup.unreflect(
+        ComputerThread::class.java.getDeclaredMethod("isFullyIdle").also { it.isAccessible = true },
+    )
+
+    fun isFullyIdle(context: ServerContext): Boolean {
+        val computerContext = computerContext.invokeExact(context) as ComputerContext
+        val computerThread = computerContext.computerScheduler() as ComputerThread
+        return isFullyIdle.invokeExact(computerThread) as Boolean
+    }
+}

projects/common/src/testMod/kotlin/dan200/computercraft/gametest/core/TestReporters.kt

@@ -35,7 +35,7 @@ class MultiTestReporter(private val reporters: List<TestReporter>) : TestReporte
  * Reports tests to a JUnit XML file. This is equivalent to [JUnitLikeTestReporter], except it ensures the destination
  * directory exists.
  */
-class JunitTestReporter constructor(destination: File) : JUnitLikeTestReporter(destination) {
+class JunitTestReporter(destination: File) : JUnitLikeTestReporter(destination) {
     override fun save(file: File) {
         try {
             Files.createDirectories(file.toPath().parent)

projects/common/src/testMod/resources/computercraft-gametest.mixins.json

@@ -11,6 +11,7 @@
         "GameTestInfoAccessor",
         "GameTestSequenceAccessor",
         "GameTestSequenceMixin",
+        "GameTestServerMixin",
         "TestCommandAccessor"
     ],
     "client": [