Add unit tests

Author: andrewlock

tracer/test/Datadog.Trace.Tests/Activity/Helpers/AllocationFreeEnumeratorTests.cs

@@ -0,0 +1,63 @@
+// <copyright file="AllocationFreeEnumeratorTests.cs" company="Datadog">
+// Unless explicitly stated otherwise all files in this repository are licensed under the Apache 2 License.
+// This product includes software developed at Datadog (https://www.datadoghq.com/). Copyright 2017 Datadog, Inc.
+// </copyright>
+
+using System.Collections;
+using System.Collections.Generic;
+using Datadog.Trace.Activity.Helpers;
+using FluentAssertions;
+using Xunit;
+
+namespace Datadog.Trace.Tests.Activity.Helpers;
+
+public class AllocationFreeEnumeratorTests
+{
+    [Fact]
+    public void CanEnumerateActivityTags()
+    {
+        var activity = new System.Diagnostics.Activity("operation");
+        activity.AddTag("key", "value");
+        activity.AddTag("key2", "value2");
+
+        var forEach = AllocationFreeEnumerator<IEnumerable<KeyValuePair<string, string>>, KeyValuePair<string, string>, int>
+           .BuildAllocationFreeForEachDelegate(activity.Tags.GetType());
+
+        int invocations = 0;
+        forEach(
+            activity.Tags,
+            ref invocations,
+            (ref state, item) =>
+            {
+                state++;
+                return true;
+            });
+
+        invocations.Should().Be(2);
+    }
+
+#if NET5_0_OR_GREATER
+    [Fact]
+    public void CanEnumerateActivityTagObjects()
+    {
+        var activity = new System.Diagnostics.Activity("operation");
+        activity.AddTag("key", 23);
+        activity.AddTag("key2", "value2");
+
+        var forEach = AllocationFreeEnumerator<IEnumerable<KeyValuePair<string, object>>, KeyValuePair<string, object>, int>
+           .BuildAllocationFreeForEachDelegate(activity.TagObjects.GetType());
+
+        int invocations = 0;
+        forEach(
+            activity.TagObjects,
+            ref invocations,
+            (ref state, item) =>
+            {
+                state++;
+                return true;
+            });
+
+        invocations.Should().Be(2);
+    }
+#endif
+}