Tests for Read_CharArrayTest reading more than necessary

src/System.IO/tests/BinaryReader/BinaryReaderTests.cs

@@ -1,4 +1,4 @@
-// Licensed to the .NET Foundation under one or more agreements.
+// 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.
 
@@ -126,7 +126,7 @@ public void Read_InvalidEncoding()
 
                 using (var reader = new BinaryReader(str, new NegEncoding()))
                 {
-                    AssertExtensions.Throws<ArgumentOutOfRangeException>("charsRemaining", () => reader.Read(new char[10], 0, 10));
+                    Assert.ThrowsAny<ArgumentException>(() => reader.Read(new char[10], 0, 10));
                 }
             }
         }
@@ -187,5 +187,46 @@ public void ReadChars(char[] source, int readLength, char[] expected)
                 }
             }
         }
+
+        // ChunkingStream returns less than requested
+        class ChunkingStream : MemoryStream
+        {
+            public override int Read(byte[] buffer, int offset, int count)
+            {
+                return base.Read(buffer, offset, count > 10 ? count - 3 : count);
+            }
+
+            public override int Read(Span<byte> destination)
+            {
+                return base.Read(destination.Length > 10 ? destination.Slice(0, destination.Length - 3) : destination);
+            }
+        }
+
+        [Theory]
+        [InlineData(false)]
+        [InlineData(true)]
+        public void ReadChars_OverReads(bool unicodeEncoding)
+        {
+            Encoding encoding = unicodeEncoding ? Encoding.Unicode : Encoding.UTF8;
+
+            char[] data1 = "hello world \ud83d\ude03!".ToCharArray(); // 14 code points, 15 chars in UTF-16, 17 bytes in UTF-8
+            uint data2 = 0xABCDEF01;
+
+            using (Stream stream = new ChunkingStream())
+            {
+                using (BinaryWriter writer = new BinaryWriter(stream, encoding, leaveOpen: true))
+                {
+                    writer.Write(data1);
+                    writer.Write(data2);
+                }
+
+                stream.Seek(0, SeekOrigin.Begin);
+                using (BinaryReader reader = new BinaryReader(stream, encoding, leaveOpen: true))
+                {
+                    Assert.Equal(data1, reader.ReadChars(data1.Length));
+                    Assert.Equal(data2, reader.ReadUInt32());
+                }
+            }
+        }
     }
 }