✅ Add unit tests for StringBuilderPolicy functionality

Author: marthijn

src/Sidio.OpenGraph.Tests/ObjectPooling/StringBuilderPolicyTests.cs

@@ -0,0 +1,93 @@
+using System.Text;
+using Microsoft.Extensions.ObjectPool;
+using Sidio.OpenGraph.ObjectPooling;
+
+namespace Sidio.OpenGraph.Tests.ObjectPooling;
+
+public sealed class StringBuilderPolicyTests
+{
+    [Fact]
+    public void Create_ShouldReturnNewInstance()
+    {
+        // Arrange
+        const int Capacity = 20;
+        var policy = new StringBuilderPolicy(Capacity);
+
+        // Act
+        var result = policy.Create();
+
+        // Assert
+        result.Should().NotBeNull();
+        result.Length.Should().Be(0);
+        result.Capacity.Should().Be(Capacity);
+    }
+
+    [Fact]
+    public void Return_ShouldClearStringBuilder()
+    {
+        // Arrange
+        var policy = new StringBuilderPolicy();
+        var stringBuilder = policy.Create();
+        stringBuilder.Append("Test");
+
+        // Act
+        var result = policy.Return(stringBuilder);
+
+        // Assert
+        stringBuilder.Length.Should().Be(0);
+        result.Should().BeTrue();
+    }
+
+    [Fact]
+    public void Return_WhenCapacityExceeded_DiscardStringBuilder()
+    {
+        // Arrange
+        const int MaxCapacity = 100;
+        var policy = new StringBuilderPolicy(10, MaxCapacity);
+        var stringBuilder = policy.Create();
+        stringBuilder.Append('a', MaxCapacity + 1);
+
+        // Act
+        var result = policy.Return(stringBuilder);
+
+        // Assert
+        result.Should().BeFalse();
+    }
+
+    [Fact]
+    public void Pool_WhenCapacityNotExceeded_UsesPolicyCorrectly()
+    {
+        // Arrange
+        var pool = new DefaultObjectPool<StringBuilder>(new StringBuilderPolicy());
+
+        // Act
+        var sb1 = pool.Get();
+        sb1.Append("Hello");
+        pool.Return(sb1);
+
+        var sb2 = pool.Get(); // should be same instance but cleared
+
+        // Assert
+        sb1.Should().BeSameAs(sb2);
+        sb2.Length.Should().Be(0);
+    }
+
+    [Fact]
+    public void Pool_WhenCapacityExceeded_UsesPolicyCorrectly()
+    {
+        // Arrange
+        const int MaxCapacity = 100;
+        var pool = new DefaultObjectPool<StringBuilder>(new StringBuilderPolicy(10, MaxCapacity));
+
+        // Act
+        var sb1 = pool.Get();
+        sb1.Append('a', MaxCapacity + 1);
+        pool.Return(sb1);
+
+        var sb2 = pool.Get(); // should be new instance
+
+        // Assert
+        sb1.Should().NotBeSameAs(sb2);
+        sb2.Length.Should().Be(0);
+    }
+}