Join a dedicated server in the automated client test.

fabric-api-base/src/testmodClient/java/net/fabricmc/fabric/test/base/client/FabricApiAutoTestClient.java

@@ -18,6 +18,7 @@
 
 import static net.fabricmc.fabric.test.base.client.FabricClientTestHelper.clickScreenButton;
 import static net.fabricmc.fabric.test.base.client.FabricClientTestHelper.closeScreen;
+import static net.fabricmc.fabric.test.base.client.FabricClientTestHelper.connectToServer;
 import static net.fabricmc.fabric.test.base.client.FabricClientTestHelper.enableDebugHud;
 import static net.fabricmc.fabric.test.base.client.FabricClientTestHelper.openGameMenu;
 import static net.fabricmc.fabric.test.base.client.FabricClientTestHelper.openInventory;
@@ -34,11 +35,15 @@
 import java.nio.file.Files;
 import java.nio.file.Path;
 
+import com.mojang.authlib.GameProfile;
 import org.spongepowered.asm.mixin.MixinEnvironment;
 
+import net.minecraft.client.MinecraftClient;
 import net.minecraft.client.gui.screen.AccessibilityOnboardingScreen;
 import net.minecraft.client.gui.screen.ConfirmScreen;
+import net.minecraft.client.gui.screen.ReconfiguringScreen;
 import net.minecraft.client.gui.screen.TitleScreen;
+import net.minecraft.client.gui.screen.multiplayer.MultiplayerScreen;
 import net.minecraft.client.gui.screen.world.CreateWorldScreen;
 import net.minecraft.client.gui.screen.world.SelectWorldScreen;
 import net.minecraft.client.option.Perspective;
@@ -114,6 +119,7 @@ private void runTest() {
 			// See if the player render events are working.
 			setPerspective(Perspective.THIRD_PERSON_BACK);
 			takeScreenshot("in_game_overworld_third_person");
+			setPerspective(Perspective.FIRST_PERSON);
 		}
 
 		{
@@ -126,6 +132,34 @@ private void runTest() {
 			openGameMenu();
 			takeScreenshot("game_menu");
 			clickScreenButton("menu.returnToMenu");
+			waitForScreen(TitleScreen.class);
+		}
+
+		try (var server = new TestDedicatedServer()) {
+			connectToServer(server);
+			waitForWorldTicks(5);
+
+			final GameProfile profile = submitAndWait(MinecraftClient::getGameProfile);
+			server.runCommand("op " + profile.getName());
+			server.runCommand("gamemode creative " + profile.getName());
+
+			waitForWorldTicks(20);
+			takeScreenshot("server_in_game");
+
+			{ // Test that we can enter and exit configuration
+				server.runCommand("debugconfig config " + profile.getName());
+				waitForScreen(ReconfiguringScreen.class);
+				takeScreenshot("server_config");
+				server.runCommand("debugconfig unconfig " + profile.getId());
+				waitForWorldTicks(1);
+			}
+
+			openGameMenu();
+			takeScreenshot("server_game_menu");
+			clickScreenButton("menu.disconnect");
+
+			waitForScreen(MultiplayerScreen.class);
+			clickScreenButton("gui.back");
 		}
 
 		{

fabric-api-base/src/testmodClient/java/net/fabricmc/fabric/test/base/client/FabricClientTestHelper.java

@@ -29,12 +29,15 @@
 import net.minecraft.client.gui.screen.Screen;
 import net.minecraft.client.gui.screen.ingame.CreativeInventoryScreen;
 import net.minecraft.client.gui.screen.ingame.InventoryScreen;
+import net.minecraft.client.gui.screen.multiplayer.ConnectScreen;
 import net.minecraft.client.gui.screen.world.LevelLoadingScreen;
 import net.minecraft.client.gui.widget.ButtonWidget;
 import net.minecraft.client.gui.widget.ClickableWidget;
 import net.minecraft.client.gui.widget.CyclingButtonWidget;
 import net.minecraft.client.gui.widget.PressableWidget;
 import net.minecraft.client.gui.widget.Widget;
+import net.minecraft.client.network.ServerAddress;
+import net.minecraft.client.network.ServerInfo;
 import net.minecraft.client.option.Perspective;
 import net.minecraft.client.util.ScreenshotRecorder;
 import net.minecraft.text.Text;
@@ -155,6 +158,14 @@ public static void setPerspective(Perspective perspective) {
 		});
 	}
 
+	public static void connectToServer(TestDedicatedServer server) {
+		submitAndWait(client -> {
+			final var serverInfo = new ServerInfo("localhost", server.getConnectionAddress(), ServerInfo.ServerType.OTHER);
+			ConnectScreen.connect(client.currentScreen, client, ServerAddress.parse(server.getConnectionAddress()), serverInfo, false, null);
+			return null;
+		});
+	}
+
 	private static void waitFor(String what, Predicate<MinecraftClient> predicate) {
 		waitFor(what, predicate, Duration.ofSeconds(10));
 	}

fabric-api-base/src/testmodClient/java/net/fabricmc/fabric/test/base/client/TestDedicatedServer.java

@@ -0,0 +1,106 @@
+/*
+ * Copyright (c) 2016, 2017, 2018, 2019 FabricMC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package net.fabricmc.fabric.test.base.client;
+
+import java.io.Closeable;
+import java.io.IOException;
+import java.io.UncheckedIOException;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+import java.time.Duration;
+import java.util.Objects;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.atomic.AtomicReference;
+import java.util.function.Function;
+
+import net.minecraft.server.Main;
+import net.minecraft.server.dedicated.MinecraftDedicatedServer;
+
+public class TestDedicatedServer implements Closeable {
+	public static final AtomicReference<MinecraftDedicatedServer> DEDICATED_SERVER_REF = new AtomicReference<>();
+	private static final Duration START_TIMEOUT = Duration.ofMinutes(5);
+
+	final ExecutorService executor = Executors.newSingleThreadExecutor();
+	MinecraftDedicatedServer server;
+
+	public TestDedicatedServer() {
+		assert DEDICATED_SERVER_REF.get() == null : "A dedicated server is already running";
+		executor.execute(this::run);
+		waitUntilReady();
+		Objects.requireNonNull(server);
+	}
+
+	public String getConnectionAddress() {
+		return "localhost:" + server.getServerPort();
+	}
+
+	public void runCommand(String command) {
+		submitAndWait(server -> {
+			server.enqueueCommand(command, server.getCommandSource());
+			return null;
+		});
+	}
+
+	private void run() {
+		setupServer();
+		Main.main(new String[]{});
+	}
+
+	private <T> CompletableFuture<T> submit(Function<MinecraftDedicatedServer, T> function) {
+		return server.submit(() -> function.apply(server));
+	}
+
+	private <T> T submitAndWait(Function<MinecraftDedicatedServer, T> function) {
+		return submit(function).join();
+	}
+
+	private void setupServer() {
+		try {
+			Files.writeString(Paths.get("eula.txt"), "eula=true");
+			Files.writeString(Paths.get("server.properties"), "online-mode=false");
+		} catch (IOException e) {
+			throw new UncheckedIOException(e);
+		}
+	}
+
+	private void waitUntilReady() {
+		long startTime = System.currentTimeMillis();
+
+		while (DEDICATED_SERVER_REF.get() == null) {
+			if (System.currentTimeMillis() - startTime > START_TIMEOUT.toMillis()) {
+				throw new RuntimeException("Timeout while waiting for the server to start");
+			}
+
+			try {
+				Thread.sleep(100);
+			} catch (InterruptedException e) {
+				throw new RuntimeException(e);
+			}
+		}
+
+		server = DEDICATED_SERVER_REF.get();
+		DEDICATED_SERVER_REF.set(null);
+	}
+
+	@Override
+	public void close() {
+		server.stop(true);
+		executor.close();
+	}
+}

fabric-api-base/src/testmodClient/java/net/fabricmc/fabric/test/base/client/mixin/MinecraftDedicatedServerMixin.java

@@ -0,0 +1,35 @@
+/*
+ * Copyright (c) 2016, 2017, 2018, 2019 FabricMC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package net.fabricmc.fabric.test.base.client.mixin;
+
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfoReturnable;
+
+import net.minecraft.server.dedicated.MinecraftDedicatedServer;
+
+import net.fabricmc.fabric.test.base.client.TestDedicatedServer;
+
+@Mixin(MinecraftDedicatedServer.class)
+public abstract class MinecraftDedicatedServerMixin {
+	@Inject(method = "setupServer", at = @At(value = "INVOKE", target = "Lnet/minecraft/server/dedicated/MinecraftDedicatedServer;loadWorld()V"))
+	private void captureServerInstance(CallbackInfoReturnable<Boolean> cir) {
+		// Capture the server instance once the server is ready to be connected to
+		TestDedicatedServer.DEDICATED_SERVER_REF.set((MinecraftDedicatedServer) (Object) this);
+	}
+}

fabric-api-base/src/testmodClient/resources/fabric-api-base-testmod.client.mixins.json

@@ -4,6 +4,7 @@
   "compatibilityLevel": "JAVA_21",
   "client": [
     "CyclingButtonWidgetAccessor",
+    "MinecraftDedicatedServerMixin",
     "ScreenAccessor"
   ],
   "injectors": {