only test where supported

Author: piksel

test/ICSharpCode.SharpZipLib.Tests/TestSupport/Streams.cs

@@ -189,6 +189,7 @@ public override long Position
 
 	}
 
+#if NETSTANDARD2_1 || NETCOREAPP3_0_OR_GREATER
 	/// <summary>
 	/// A <see cref="Stream"/> that does not support non-async operations.
 	/// </summary>
@@ -210,11 +211,10 @@ public class MemoryStreamWithoutSync : Stream
 
 		public override void Flush() => throw new NotSupportedException($"Non-async call to {nameof(Flush)}");
 
-#if NETSTANDARD2_1 || NETCOREAPP3_0_OR_GREATER
+
 		public override void CopyTo(Stream destination, int bufferSize) => throw new NotSupportedException($"Non-async call to {nameof(CopyTo)}");
 		public override void Write(ReadOnlySpan<byte> buffer) => throw new NotSupportedException($"Non-async call to {nameof(Write)}");
 		public override int Read(Span<byte> buffer) => throw new NotSupportedException($"Non-async call to {nameof(Read)}");
-#endif
 
 		public override void Write(byte[] buffer, int offset, int count) => throw new NotSupportedException($"Non-async call to {nameof(Write)}");
 		public override void WriteByte(byte value) => throw new NotSupportedException($"Non-async call to {nameof(Write)}");
@@ -233,11 +233,8 @@ public override async Task CopyToAsync(Stream destination, int bufferSize, Cance
 		public override Task FlushAsync(CancellationToken cancellationToken) => TaskFromBlocking(() => _inner.Flush());
 		public override Task WriteAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken) => TaskFromBlocking(() => _inner.Write(buffer, offset, count));
 		public override Task<int> ReadAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken) => Task.FromResult(_inner.Read(buffer, offset, count));
-
-#if NETSTANDARD2_1 || NETCOREAPP3_0_OR_GREATER
 		public override ValueTask WriteAsync(ReadOnlyMemory<byte> buffer, CancellationToken cancellationToken = default) => ValueTaskFromBlocking(() => _inner.Write(buffer.Span));
 		public override ValueTask<int> ReadAsync(Memory<byte> buffer, CancellationToken cancellationToken = default) => ValueTask.FromResult(_inner.Read(buffer.Span));
-#endif
 
 		static Task TaskFromBlocking(Action action)
 		{
@@ -261,6 +258,7 @@ public override void SetLength(long value)
 			_inner.SetLength(value);
 		}
 	}
+#endif
 
 	/// <summary>
 	/// A <see cref="Stream"/> that cannot be read but supports infinite writes.

test/ICSharpCode.SharpZipLib.Tests/Zip/ZipStreamAsyncTests.cs

@@ -15,7 +15,7 @@ public class ZipStreamAsyncTests
 		[Category("Async")]
 		public async Task WriteZipStreamUsingAsync()
 		{
-#if NETCOREAPP3_1_OR_GREATER
+#if NETSTANDARD2_1 || NETCOREAPP3_0_OR_GREATER
 			await using var ms = new MemoryStream();
 
 			await using (var outStream = new ZipOutputStream(ms){IsStreamOwner = false})
@@ -126,6 +126,7 @@ public async Task WriteReadOnlyZipStreamAsync ()
 		[Category("Async")]
 		public async Task WriteZipStreamToAsyncOnlyStream ()
 		{
+#if NETSTANDARD2_1 || NETCOREAPP3_0_OR_GREATER
 			await using(var ms = new MemoryStreamWithoutSync()){
 				await using(var outStream = new ZipOutputStream(ms) { IsStreamOwner = false })
 				{
@@ -141,6 +142,10 @@ public async Task WriteZipStreamToAsyncOnlyStream ()
 
 				ZipTesting.AssertValidZip(new MemoryStream(ms.ToArray()));
 			}
+#else
+			await Task.CompletedTask;
+			Assert.Ignore("AsyncDispose is not supported");
+#endif
 		}
 
 	}