Get the tests passing again

buffer-api/src/main/java/io/netty/buffer/api/CompositeBuffer.java

@@ -891,6 +891,9 @@ public final class CompositeBuffer extends ResourceSupport<Buffer, CompositeBuff
             throw new IllegalArgumentException("The split offset cannot be greater than the buffer capacity, " +
                     "but the split offset was " + splitOffset + ", and capacity is " + capacity() + '.');
         }
+        if (!isAccessible()) {
+            throw attachTrace(bufferIsClosed(this));
+        }
         if (!isOwned()) {
             throw new IllegalStateException("Cannot split a buffer that is not owned.");
         }

buffer-api/src/main/java/io/netty/buffer/api/bytebuffer/NioBuffer.java

@@ -459,6 +459,9 @@ class NioBuffer extends ResourceSupport<Buffer, NioBuffer> implements Buffer, Re
             throw new IllegalArgumentException("The split offset cannot be greater than the buffer capacity, " +
                     "but the split offset was " + splitOffset + ", and capacity is " + capacity() + '.');
         }
+        if (!isAccessible()) {
+            throw attachTrace(bufferIsClosed(this));
+        }
         if (!isOwned()) {
             throw attachTrace(new IllegalStateException("Cannot split a buffer that is not owned."));
         }

buffer-api/src/main/java/io/netty/buffer/api/internal/ResourceSupport.java

@@ -108,6 +108,9 @@ public abstract class ResourceSupport<I extends Resource<I>, T extends ResourceS
      */
     @Override
     public final Send<I> send() {
+        if (acquires < 0) {
+            throw attachTrace(createResourceClosedException());
+        }
         if (!isOwned()) {
             throw notSendableException();
         }

buffer-api/src/main/java/io/netty/buffer/api/unsafe/UnsafeBuffer.java

@@ -506,6 +506,9 @@ class UnsafeBuffer extends ResourceSupport<Buffer, UnsafeBuffer> implements Buff
             throw new IllegalArgumentException("The split offset cannot be greater than the buffer capacity, " +
                     "but the split offset was " + splitOffset + ", and capacity is " + capacity() + '.');
         }
+        if (!isAccessible()) {
+            throw attachTrace(bufferIsClosed(this));
+        }
         if (!isOwned()) {
             throw attachTrace(new IllegalStateException("Cannot split a buffer that is not owned."));
         }

buffer-memseg/src/main/java/io/netty/buffer/api/memseg/MemSegBuffer.java

@@ -584,6 +584,9 @@ class MemSegBuffer extends ResourceSupport<Buffer, MemSegBuffer> implements Buff
             throw new IllegalArgumentException("The split offset cannot be greater than the buffer capacity, " +
                     "but the split offset was " + splitOffset + ", and capacity is " + capacity() + '.');
         }
+        if (!isAccessible()) {
+            throw attachTrace(bufferIsClosed(this));
+        }
         if (!isOwned()) {
             throw attachTrace(new IllegalStateException("Cannot split a buffer that is not owned."));
         }

buffer-tests/src/test/java/io/netty/buffer/api/tests/BufferSendTest.java

@@ -17,6 +17,7 @@ package io.netty.buffer.api.tests;
 
 import io.netty.buffer.api.Buffer;
 import io.netty.buffer.api.BufferAllocator;
+import io.netty.buffer.api.BufferClosedException;
 import io.netty.buffer.api.BufferRef;
 import io.netty.buffer.api.Send;
 import io.netty.buffer.api.internal.ResourceSupport;
@@ -110,9 +111,9 @@ public class BufferSendTest extends BufferTestSupport {
         try (BufferAllocator allocator = fixture.createAllocator();
              Buffer buf = allocator.allocate(8)) {
             var send = buf.send();
-            var exc = assertThrows(IllegalStateException.class, () -> buf.send());
+            var exc = assertThrows(BufferClosedException.class, () -> buf.send());
             send.receive().close();
-            assertThat(exc).hasMessageContaining("Cannot send()");
+            assertThat(exc).hasMessageContaining("closed");
         }
     }