Add and use limited capacity queue

osu.Game.Tests/NonVisual/LimitedCapacityQueueTest.cs

@@ -0,0 +1,98 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System;
+using NUnit.Framework;
+using osu.Game.Rulesets.Difficulty.Utils;
+
+namespace osu.Game.Tests.NonVisual
+{
+    [TestFixture]
+    public class LimitedCapacityQueueTest
+    {
+        private const int capacity = 3;
+
+        private LimitedCapacityQueue<int> queue;
+
+        [SetUp]
+        public void SetUp()
+        {
+            queue = new LimitedCapacityQueue<int>(capacity);
+        }
+
+        [Test]
+        public void TestEmptyQueue()
+        {
+            Assert.AreEqual(0, queue.Count);
+
+            Assert.Throws<ArgumentOutOfRangeException>(() => _ = queue[0]);
+
+            Assert.Throws<InvalidOperationException>(() => _ = queue.Dequeue());
+
+            int count = 0;
+            foreach (var _ in queue)
+                count++;
+
+            Assert.AreEqual(0, count);
+        }
+
+        [TestCase(1)]
+        [TestCase(2)]
+        [TestCase(3)]
+        public void TestBelowCapacity(int count)
+        {
+            for (int i = 0; i < count; ++i)
+                queue.Enqueue(i);
+
+            Assert.AreEqual(count, queue.Count);
+
+            for (int i = 0; i < count; ++i)
+                Assert.AreEqual(i, queue[i]);
+
+            int j = 0;
+            foreach (var item in queue)
+                Assert.AreEqual(j++, item);
+
+            for (int i = queue.Count; i < queue.Count + capacity; i++)
+                Assert.Throws<ArgumentOutOfRangeException>(() => _ = queue[i]);
+        }
+
+        [TestCase(4)]
+        [TestCase(5)]
+        [TestCase(6)]
+        public void TestEnqueueAtFullCapacity(int count)
+        {
+            for (int i = 0; i < count; ++i)
+                queue.Enqueue(i);
+
+            Assert.AreEqual(capacity, queue.Count);
+
+            for (int i = 0; i < queue.Count; ++i)
+                Assert.AreEqual(count - capacity + i, queue[i]);
+
+            int j = count - capacity;
+            foreach (var item in queue)
+                Assert.AreEqual(j++, item);
+
+            for (int i = queue.Count; i < queue.Count + capacity; i++)
+                Assert.Throws<ArgumentOutOfRangeException>(() => _ = queue[i]);
+        }
+
+        [TestCase(4)]
+        [TestCase(5)]
+        [TestCase(6)]
+        public void TestDequeueAtFullCapacity(int count)
+        {
+            for (int i = 0; i < count; ++i)
+                queue.Enqueue(i);
+
+            for (int i = 0; i < capacity; ++i)
+            {
+                Assert.AreEqual(count - capacity + i, queue.Dequeue());
+                Assert.AreEqual(2 - i, queue.Count);
+            }
+
+            Assert.Throws<InvalidOperationException>(() => queue.Dequeue());
+        }
+    }
+}