Add integration test. Run with ./gradlew runIntegrationTest

src/integration-test/java/com/replaymod/replay/OpenReplayViewer.java

@@ -0,0 +1,15 @@
+package com.replaymod.replay;
+
+import com.replaymod.core.AbstractTask;
+import com.replaymod.replay.gui.screen.GuiReplayViewer;
+import net.minecraft.client.gui.GuiMainMenu;
+
+public class OpenReplayViewer extends AbstractTask {
+    @Override
+    protected void init() {
+        expectGui(GuiMainMenu.class, mainMenu -> {
+            click("Replay Viewer");
+            expectGui(GuiReplayViewer.class, replayViewer -> future.set(null));
+        });
+    }
+}