Tests for AutoExpandingMemory class

tests/ImageSharp.Tests/Memory/AutoExpandingMemoryTests.cs

@@ -0,0 +1,54 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+using SixLabors.ImageSharp.Memory;
+
+// ReSharper disable InconsistentNaming
+namespace SixLabors.ImageSharp.Tests.Memory;
+
+public class AutoExpandingMemoryTests
+{
+    private readonly Configuration configurtion = Configuration.Default;
+
+    [Theory]
+    [InlineData(1000, 2000)]
+    [InlineData(1000, 1000)]
+    [InlineData(200, 1000)]
+    [InlineData(200, 200)]
+    [InlineData(200, 100)]
+    public void ExpandToRequestedCapacity(int initialCapacity, int requestedCapacity)
+    {
+        AutoExpandingMemory<byte> memory = new(this.configurtion, initialCapacity);
+        Span<byte> span = memory.GetSpan(requestedCapacity);
+        Assert.Equal(requestedCapacity, span.Length);
+    }
+
+    [Theory]
+    [InlineData(1000, 2000)]
+    [InlineData(1000, 1000)]
+    [InlineData(200, 1000)]
+    [InlineData(200, 200)]
+    [InlineData(200, 100)]
+    public void KeepDataWhileExpanding(int initialCapacity, int requestedCapacity)
+    {
+        AutoExpandingMemory<byte> memory = new(this.configurtion, initialCapacity);
+        Span<byte> firstSpan = memory.GetSpan(initialCapacity);
+        firstSpan[1] = 1;
+        firstSpan[2] = 2;
+        firstSpan[3] = 3;
+        Span<byte> expandedSpan = memory.GetSpan(requestedCapacity);
+        Assert.Equal(3, firstSpan[3]);
+        Assert.Equal(firstSpan[3], expandedSpan[3]);
+    }
+
+    [Theory]
+    [InlineData(1, -1)]
+    [InlineData(1, 0)]
+    [InlineData(-2, 1)]
+    [InlineData(-2, 0)]
+    public void Guards(int initialCapacity, int requestedCapacity) =>
+        Assert.Throws<ArgumentOutOfRangeException>(() =>
+        {
+            AutoExpandingMemory<byte> memory = new(this.configurtion, initialCapacity);
+            _ = memory.GetSpan(requestedCapacity);
+        });
+}