Fix #1162

Author: vbreuss

src/TestableIO.System.IO.Abstractions/FileSystemStream.cs

@@ -223,15 +223,6 @@ protected override void Dispose(bool disposing)
             base.Dispose(disposing);
         }
 
-#if FEATURE_ASYNC_FILE
-        /// <inheritdoc cref="Stream.DisposeAsync()" />
-        public override async ValueTask DisposeAsync()
-        {
-            await _stream.DisposeAsync();
-            await base.DisposeAsync();
-        }
-#endif
-
         /// <summary>
         /// Allows to cast the internal Stream to a FileStream
         /// </summary>

tests/TestableIO.System.IO.Abstractions.TestingHelpers.Tests/MockFileStreamTests.cs

@@ -283,6 +283,18 @@ public void MockFileStream_Null_ShouldReturnSingletonObject()
 
             Assert.That(result1, Is.SameAs(result2));
         }
+        
+        #if FEATURE_ASYNC_FILE
+        [Test]
+        public async Task MockFileStream_DisposeAsync_ShouldNotThrow()
+        {
+            var fileSystem = new MockFileSystem();
+            fileSystem.File.WriteAllText("foo.txt", "");
+            {
+                await using var reportStream = fileSystem.File.OpenRead("foo.txt");
+            }
+        }
+        #endif
 
         [Test]
         public void MockFileStream_Null_ShouldHaveExpectedProperties()