Unit tests for CloCollectorFuture

Author: CursedFlames

src/main/java/io/github/opencubicchunks/cubicchunks/server/level/CloCollectorFuture.java

@@ -24,7 +24,7 @@ public class CloCollectorFuture extends CompletableFuture<List<Either<CloAccess,
 
     private final Either<CloAccess, ChunkHolder.ChunkLoadingFailure>[] results;
     // Vanilla expects that the center chunk is in the middle of the list; this is not the case for cubes, so we manually swap the center cube to the middle
-    private AtomicInteger indexToBeSwappedWithCenterIndex = new AtomicInteger();
+    private AtomicInteger indexToBeSwappedWithCenterIndex = new AtomicInteger(-1);
 
     public CloCollectorFuture(int size) {
         this.size = size;
@@ -37,7 +37,10 @@ public void add(Either<CloAccess, ChunkHolder.ChunkLoadingFailure> either, @Null
         } else {
             int i = index.getAndIncrement();
             if (isCenterCube) {
-                indexToBeSwappedWithCenterIndex.set(i);
+                int oldValue = indexToBeSwappedWithCenterIndex.getAndSet(i);
+                if (oldValue != -1) {
+                    throw new IllegalStateException("Tried to set center cube when center cube was already set");
+                }
             }
             results[i] = either;
         }
@@ -49,6 +52,9 @@ public void add(Either<CloAccess, ChunkHolder.ChunkLoadingFailure> either, @Null
 
     private void done() {
         int i = indexToBeSwappedWithCenterIndex.get();
+        if (i == -1) {
+            throw new IllegalStateException("All Clos were received but no center cube was set");
+        }
         int j = results.length / 2;
         var results = Arrays.asList(this.results);
         Collections.swap(results, i, j);

src/test/java/io/github/opencubicchunks/cubicchunks/test/server/level/TestCloCollectorFuture.java

@@ -0,0 +1,64 @@
+package io.github.opencubicchunks.cubicchunks.test.server.level;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNotSame;
+import static org.junit.jupiter.api.Assertions.assertSame;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.mockito.Mockito.mock;
+
+import com.mojang.datafixers.util.Either;
+import io.github.opencubicchunks.cubicchunks.server.level.CloCollectorFuture;
+import io.github.opencubicchunks.cubicchunks.testutils.BaseTest;
+import io.github.opencubicchunks.cubicchunks.world.level.chunklike.CloAccess;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.TestInstance;
+
+@TestInstance(TestInstance.Lifecycle.PER_CLASS)
+public class TestCloCollectorFuture extends BaseTest {
+    @Test public void testFutureCompletion() throws Exception {
+        for (int i = 0; i < 9; i++) { // Run nine times, putting the center cube at each index
+            var future = new CloCollectorFuture(9);
+            CloAccess centerCube = mock();
+            CloAccess others = mock();
+            for (int j = 0; j < 9; j++) {
+                assertFalse(future.isDone(), "future shouldn't complete until all Clos are added");
+                future.add(Either.left(j == i ? centerCube : others), null, j == i);
+            }
+            assertTrue(future.isDone(), "future should be complete once all Clos are added");
+            assertSame(future.get().get(4).left().get(), centerCube, "centerCube should be at center index");
+            for (int j = 0; j < 9; j++) {
+                if (j == 4) continue;
+                assertNotSame(future.get().get(j).left().get(), centerCube, "reference to centerCube should not be duplicated at any other index");
+            }
+        }
+    }
+
+    @Test public void testMultipleCenterCubes() {
+        var future = new CloCollectorFuture(9);
+        CloAccess cloAccess = mock();
+        future.add(Either.left(cloAccess), null, true);
+        assertThrows(IllegalStateException.class, () -> future.add(Either.left(cloAccess), null, true), "trying to set centerCube multiple times should throw an exception");
+    }
+
+    @Test public void testMissingCenterCube() {
+        var future = new CloCollectorFuture(9);
+        CloAccess cloAccess = mock();
+        for (int i = 0; i < 8; i++) {
+            future.add(Either.left(cloAccess), null, false);
+        }
+        assertThrows(IllegalStateException.class, () -> future.add(Either.left(cloAccess), null, false), "completing without having set centerCube should throw an exception");
+    }
+
+    @Test public void testFutureExceptionPropagation() {
+        for (int i = 0; i < 9; i++) { // Run nine times, throwing an exception at each index
+            var future = new CloCollectorFuture(9);
+            var exception = new Exception("test exception");
+            CloAccess cloAccess = mock();
+            for (int j = 0; j < 9; j++) {
+                future.add(Either.left(cloAccess), i == j ? exception : null, false);
+            }
+            assertTrue(future.isCompletedExceptionally(), "future should complete exceptionally upon receiving an Exception");
+        }
+    }
+}