Cleanup ImmutableArray tests

src/Common/tests/System/Collections/DelegateEqualityComparer.cs

@@ -0,0 +1,36 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+
+namespace System.Collections.Tests
+{
+    internal sealed class DelegateEqualityComparer<T> : IEqualityComparer<T>, IEqualityComparer
+    {
+        private readonly Func<T, T, bool> _equals;
+        private readonly Func<T, int> _getHashCode;
+        private readonly Func<object, object, bool> _objectEquals;
+        private readonly Func<object, int> _objectGetHashCode;
+
+        public DelegateEqualityComparer(
+            Func<T, T, bool> equals = null,
+            Func<T, int> getHashCode = null,
+            Func<object, object, bool> objectEquals = null,
+            Func<object, int> objectGetHashCode = null)
+        {
+            _equals = equals ?? ((x, y) => { throw new NotImplementedException(); });
+            _getHashCode = getHashCode ?? (obj => { throw new NotImplementedException(); });
+            _objectEquals = objectEquals ?? ((x, y) => { throw new NotImplementedException(); });
+            _objectGetHashCode = objectGetHashCode ?? (obj => { throw new NotImplementedException(); });
+        }
+
+        public bool Equals(T x, T y) => _equals(x, y);
+
+        public int GetHashCode(T obj) => _getHashCode(obj);
+
+        bool IEqualityComparer.Equals(object x, object y) => _objectEquals(x, y);
+
+        int IEqualityComparer.GetHashCode(object obj) => _objectGetHashCode(obj);
+    }
+}

src/System.Collections.Immutable/src/System/Collections/Immutable/ImmutableArray_1.cs

@@ -170,7 +170,7 @@ public bool IsEmpty
         }
 
         /// <summary>
-        /// Gets the number of array in the collection.
+        /// Gets the number of elements in the array.
         /// </summary>
         [DebuggerBrowsable(DebuggerBrowsableState.Never)]
         public int Length