diff --git a/Iced.UnitTests/Intel/InstructionTests/InstructionListTests.cs b/Iced.UnitTests/Intel/InstructionTests/InstructionListTests.cs
index 39a1ab7d9..f127e1aed 100644
--- a/Iced.UnitTests/Intel/InstructionTests/InstructionListTests.cs
+++ b/Iced.UnitTests/Intel/InstructionTests/InstructionListTests.cs
@@ -23,6 +23,7 @@ SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 #if !NO_ENCODER
 using System;
+using System.Collections;
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
 using System.Linq;
@@ -400,6 +401,8 @@ namespace Iced.UnitTests.Intel.InstructionTests {
 
 		enum InsertRangeKind {
 			IEnumerable,
+			Array,
+			IList,
 			ReadOnlyList,
 			InstructionList,
 
@@ -456,9 +459,17 @@ namespace Iced.UnitTests.Intel.InstructionTests {
 				// IEnumerable<Instruction> code path
 				return array.AsEnumerable();
 
+			case InsertRangeKind.Array:
+				// Instruction[] code path (none at the moment)
+				return array;
+
+			case InsertRangeKind.IList:
+				// IList<Instruction> code path
+				return new IListImpl<Instruction>(array);
+
 			case InsertRangeKind.ReadOnlyList:
 				// IReadOnlyList<Instruction> code path
-				return new ReadOnlyCollection<Instruction>(array);
+				return new IReadOnlyListImpl<Instruction>(array);
 
 			case InsertRangeKind.InstructionList:
 				// InstructionList code path
@@ -470,6 +481,36 @@ namespace Iced.UnitTests.Intel.InstructionTests {
 			}
 		}
 
+		sealed class IListImpl<T> : IList<T> {
+			readonly T[] array;
+			public IListImpl(T[] array) => this.array = array;
+			public int Count => array.Length;
+			public T this[int index] {
+				get => array[index];
+				set => throw new NotImplementedException();
+			}
+			public bool IsReadOnly => throw new NotImplementedException();
+			public int IndexOf(T item) => throw new NotImplementedException();
+			public void Insert(int index, T item) => throw new NotImplementedException();
+			public void RemoveAt(int index) => throw new NotImplementedException();
+			public void Add(T item) => throw new NotImplementedException();
+			public void Clear() => throw new NotImplementedException();
+			public bool Contains(T item) => throw new NotImplementedException();
+			public bool Remove(T item) => throw new NotImplementedException();
+			public void CopyTo(T[] array, int arrayIndex) => throw new NotImplementedException();
+			public IEnumerator<T> GetEnumerator() => throw new NotImplementedException();
+			IEnumerator IEnumerable.GetEnumerator() => throw new NotImplementedException();
+		}
+
+		sealed class IReadOnlyListImpl<T> : IReadOnlyList<T> {
+			readonly T[] array;
+			public IReadOnlyListImpl(T[] array) => this.array = array;
+			public int Count => array.Length;
+			public T this[int index] => array[index];
+			public IEnumerator<T> GetEnumerator() => throw new NotImplementedException();
+			IEnumerator IEnumerable.GetEnumerator() => throw new NotImplementedException();
+		}
+
 		[Theory]
 		[MemberData(nameof(AddRange_works_Data))]
 		void AddRange_works(InstructionList list, IEnumerable<Instruction> inserted, Instruction[] expected) {