fix: resolve issue with IsEquivalentTo for nested collections in records

TUnit.Assertions.Tests/Bugs/Tests3489.cs

@@ -0,0 +1,86 @@
+namespace TUnit.Assertions.Tests.Bugs;
+
+/// <summary>
+/// Tests for issue #3489: IsEquivalentTo does not work properly with nested collections in records
+/// </summary>
+public class Tests3489
+{
+    [Test]
+    public async Task IsEquivalentTo_WithNestedCollections_InRecords_ShouldSucceed()
+    {
+        // Arrange - Create identical hierarchical structures
+        var actual = new List<Person>
+        {
+            new()
+            {
+                Name = "Parent1",
+                Children =
+                [
+                    new Person { Name = "Child1", Children = [] },
+                    new Person { Name = "Child2", Children = [] }
+                ]
+            },
+            new()
+            {
+                Name = "Parent2",
+                Children = [new Person { Name = "Child3", Children = [] }]
+            }
+        };
+
+        var expected = new List<Person>
+        {
+            new()
+            {
+                Name = "Parent1",
+                Children =
+                [
+                    new Person { Name = "Child1", Children = [] },
+                    new Person { Name = "Child2", Children = [] }
+                ]
+            },
+            new()
+            {
+                Name = "Parent2",
+                Children = [new Person { Name = "Child3", Children = [] }]
+            }
+        };
+
+        // Act & Assert - Should recognize structural equivalence despite different List instances
+        await Assert.That(actual).IsEquivalentTo(expected);
+    }
+
+    [Test]
+    public async Task IsEquivalentTo_WithNestedCollections_InRecords_DifferentData_ShouldFail()
+    {
+        // Arrange
+        var actual = new List<Person>
+        {
+            new()
+            {
+                Name = "Parent1",
+                Children = [new Person { Name = "Child1", Children = [] }]
+            }
+        };
+
+        var expected = new List<Person>
+        {
+            new()
+            {
+                Name = "Parent1",
+                Children = [new Person { Name = "DifferentChild", Children = [] }]
+            }
+        };
+
+        // Act & Assert - Should fail when actual data is different
+        var exception = await Assert.ThrowsAsync<TUnitAssertionException>(
+            async () => await Assert.That(actual).IsEquivalentTo(expected));
+
+        await Assert.That(exception).IsNotNull();
+    }
+
+    private sealed record Person
+    {
+        public required string Name { get; init; }
+        public required List<Person> Children { get; init; }
+    }
+}

TUnit.Assertions/Conditions/Helpers/StructuralEqualityComparer.cs

@@ -41,11 +41,6 @@ public bool Equals(T? x, T? y)
             return EqualityComparer<T>.Default.Equals(x, y);
         }
 
-        if (typeof(IEquatable<T>).IsAssignableFrom(type))
-        {
-            return ((IEquatable<T>)x).Equals(y);
-        }
-
         return CompareStructurally(x, y, new HashSet<object>(new ReferenceEqualityComparer()));
     }