test: add unit tests for FastFairPriorityQueue functionality

Author: twisti-dev

surf-cloud-api/surf-cloud-api-common/src/main/kotlin/dev/slne/surf/cloud/api/common/util/queue/FastFairPriorityQueue.kt

@@ -167,7 +167,10 @@ class FastFairPriorityQueue<T>(private val prioCmp: Comparator<in T>) : Abstract
     fun snapshot(): ObjectArrayList<T> {
         val size = heap.size()
         if (size == 0) return ObjectArrayList()
-        val buf = heap.backing().copyOfRange(0, size + 1)
+
+        val raw = heap.backing()
+        val buf: Array<Entry<T>?> = arrayOfNulls(size)
+        System.arraycopy(raw, 0, buf, 0, size)
         ObjectArrays.stableSort(buf, entryCmp)
 
         val result = ObjectArrayList<T>(size)
@@ -192,7 +195,7 @@ class FastFairPriorityQueue<T>(private val prioCmp: Comparator<in T>) : Abstract
     private class ExposedHeap<E>(
         cmp: Comparator<E>
     ) : ObjectHeapPriorityQueue<E>(cmp) {
-        fun backing(): Array<E?> = heap
+        fun backing(): Array<Any?> = heap as Array<Any?>
 
         companion object {
             @Serial

surf-cloud-standalone/src/test/java/dev/slne/surf/cloud/api/common/util/queue/FastFairPriorityQueueTest.kt

@@ -0,0 +1,44 @@
+package dev.slne.surf.cloud.api.common.util.queue
+
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Test
+
+class FastFairPriorityQueueTest {
+
+    @Test
+    fun `fifo order for equal priority`() {
+        val queue = FastFairPriorityQueue<Int>(Comparator.naturalOrder())
+        queue.offer(1)
+        queue.offer(1)
+        queue.offer(1)
+
+        val first = queue.poll()
+        val second = queue.poll()
+        val third = queue.poll()
+
+        assertEquals(listOf(1, 1, 1), listOf(first, second, third))
+    }
+
+    @Test
+    fun `addFirst inserts ahead of others`() {
+        val queue = FastFairPriorityQueue<Int>(Comparator.naturalOrder())
+        queue.offer(1)
+        queue.addFirst(1)
+        queue.offer(2)
+
+        assertEquals(1, queue.poll())
+        assertEquals(1, queue.poll())
+        assertEquals(2, queue.poll())
+    }
+
+    @Test
+    fun `snapshot returns ordered list`() {
+        val queue = FastFairPriorityQueue<Int>(Comparator.naturalOrder())
+        queue.offer(3)
+        queue.offer(1)
+        queue.offer(2)
+
+        assertEquals(listOf(1, 2, 3), queue.snapshot().toList())
+    }
+
+}