diff --git a/MoreLinq.Test/AssertTest.cs b/MoreLinq.Test/AssertTest.cs
index ecd288ce6..72ace92ae 100644
--- a/MoreLinq.Test/AssertTest.cs
+++ b/MoreLinq.Test/AssertTest.cs
@@ -33,14 +33,15 @@ public void AssertIsLazy()
         [Test]
         public void AssertSequenceWithValidAllElements()
         {
-            var source = new[] { 2, 4, 6, 8 };
-            source.Assert(n => n % 2 == 0).AssertSequenceEqual(source);
+            var xs = new[] { 2, 4, 6, 8 };
+            using var source = TestingSequence.Of(xs);
+            source.Assert(n => n % 2 == 0).AssertSequenceEqual(xs);
         }
 
         [Test]
         public void AssertSequenceWithValidSomeInvalidElements()
         {
-            var source = new[] { 2, 4, 6, 7, 8, 9 };
+            using var source = TestingSequence.Of(2, 4, 6, 7, 8, 9);
             Assert.That(() => source.Assert(n => n % 2 == 0).Consume(),
                         Throws.InvalidOperationException);
         }
@@ -48,7 +49,7 @@ public void AssertSequenceWithValidSomeInvalidElements()
         [Test]
         public void AssertSequenceWithInvalidElementsAndCustomErrorReturningNull()
         {
-            var source = new[] { 2, 4, 6, 7, 8, 9 };
+            using var source = TestingSequence.Of(2, 4, 6, 7, 8, 9);
             Assert.That(() => source.Assert(n => n % 2 == 0, _ => null!).Consume(),
                         Throws.InvalidOperationException);
         }
@@ -56,7 +57,7 @@ public void AssertSequenceWithInvalidElementsAndCustomErrorReturningNull()
         [Test]
         public void AssertSequenceWithInvalidElementsAndCustomError()
         {
-            var source = new[] { 2, 4, 6, 7, 8, 9 };
+            using var source = TestingSequence.Of(2, 4, 6, 7, 8, 9);
             Assert.That(() =>
                 source.Assert(n => n % 2 == 0, n => new ValueException(n)).Consume(),
                 Throws.TypeOf<ValueException>()
diff --git a/MoreLinq.Test/AtLeastTest.cs b/MoreLinq.Test/AtLeastTest.cs
index 83f6093ad..cb92815ce 100644
--- a/MoreLinq.Test/AtLeastTest.cs
+++ b/MoreLinq.Test/AtLeastTest.cs
@@ -17,6 +17,7 @@
 
 namespace MoreLinq.Test
 {
+    using System;
     using NUnit.Framework;
     using System.Collections.Generic;
 
@@ -49,8 +50,13 @@ from e in new[]
                 .SetName($"{{m}}({k}[{e.Size}], {e.Count})");
 
         [TestCaseSource(nameof(AtLeastSource))]
-        public bool AtLeast(SourceKind sourceKind, int sequenceSize, int atLeastAssertCount) =>
-            Enumerable.Range(0, sequenceSize).ToSourceKind(sourceKind).AtLeast(atLeastAssertCount);
+        public bool AtLeast(SourceKind sourceKind, int sequenceSize, int atLeastAssertCount)
+        {
+            var xs = Enumerable.Range(0, sequenceSize);
+            var source = xs.ToSourceKind(sourceKind);
+            using (source as IDisposable) // primarily for `TestingSequence<>`
+                return source.AtLeast(atLeastAssertCount);
+        }
 
         [Test]
         public void AtLeastDoesNotIterateUnnecessaryElements()
diff --git a/MoreLinq.Test/TestExtensions.cs b/MoreLinq.Test/TestExtensions.cs
index 706641f1b..4c9c52858 100644
--- a/MoreLinq.Test/TestExtensions.cs
+++ b/MoreLinq.Test/TestExtensions.cs
@@ -92,14 +92,14 @@ internal static IEnumerable<T> ToSourceKind<T>(this IEnumerable<T> input, Source
             sourceKind switch
 #pragma warning restore IDE0072 // Add missing cases
             {
-                SourceKind.Sequence => input.Select(x => x),
+                SourceKind.Sequence => input.AsTestingSequence(),
                 var kind => input.ToList().AsSourceKind(kind)
             };
 
         internal static IEnumerable<T> AsSourceKind<T>(this List<T> input, SourceKind sourceKind) =>
             sourceKind switch
             {
-                SourceKind.Sequence => input.Select(x => x),
+                SourceKind.Sequence => input.AsTestingSequence(),
                 SourceKind.BreakingList => new BreakingList<T>(input),
                 SourceKind.BreakingReadOnlyList => new BreakingReadOnlyList<T>(input),
                 SourceKind.BreakingCollection => new BreakingCollection<T>(input),