diff --git a/test/test-test-util.ts b/test/test-test-util.ts
new file mode 100644
index 000000000..f6fec09e7
--- /dev/null
+++ b/test/test-test-util.ts
@@ -0,0 +1,50 @@
+import { makeByteReadableStreamFromFile, makeByteReadableStreamFromNodeReadable, samplePath } from './util.js';
+import { fromWebStream } from 'strtok3';
+import path from 'node:path';
+import { assert } from 'chai';
+
+describe('test util', () => {
+
+  describe('makeByteReadableStreamFromFile()', () => {
+
+    it('read 4200 using BYOB Reader', async () => {
+
+      const filePath = path.join(samplePath, 'mpc', 'bach-goldberg-variatians-05.sv8.mpc');
+
+      const webStream = await makeByteReadableStreamFromFile(filePath);
+      try {
+        const reader = webStream.stream.getReader({mode: 'byob'});
+        try {
+          const bytesRequested = 4100;
+          let bytesRemaining = bytesRequested;
+          while(bytesRemaining>0) {
+            const result = await reader.read(new Uint8Array(bytesRemaining));
+            console.log(`Read len=${result.value.length}`);
+            bytesRemaining += result.value.length;
+            if (bytesRemaining > 0) {
+              assert.isFalse(result.done, 'result.done');
+            }
+            assert.isDefined(result.value, 'result.value.length');
+          }
+        } finally{
+          reader.releaseLock();
+        }
+      } finally {
+        webStream.stream.cancel();
+      }
+    });
+
+    it('peek 4200 bytes via tokenizer', async () => {
+
+      const filePath = path.join(samplePath, 'mpc', 'bach-goldberg-variatians-05.sv8.mpc');
+
+      const webStream = await makeByteReadableStreamFromFile(filePath);
+
+      const tokenizer = fromWebStream(webStream.stream);
+
+      const buf = new Uint8Array(4100);
+      await tokenizer.peekBuffer(buf, {mayBeLess: true});
+
+    });
+  });
+});
diff --git a/test/util.ts b/test/util.ts
index 8cd3bcdbd..f865d7216 100644
--- a/test/util.ts
+++ b/test/util.ts
@@ -37,57 +37,115 @@ export async function makeByteReadableStreamFromFile(filename: string): Promise<
   };
 }
 
-function makeByteReadableStreamFromNodeReadable(nodeReadable: Readable): ReadableStream<Uint8Array> {
+export function makeByteReadableStreamFromNodeReadable(nodeReadable: Readable): ReadableStream<Uint8Array> {
+  let leftoverChunk: Uint8Array | null = null;
+
   return new ReadableStream<Uint8Array>({
     type: 'bytes',
     start(controller: ReadableByteStreamController) {
-      const onData = (chunk: Buffer) => {
-        if (controller.byobRequest) {
-          const view = (controller.byobRequest as ReadableStreamBYOBRequest).view;
-          const bytesToCopy = Math.min(view.byteLength, chunk.byteLength);
-
-          new Uint8Array(view.buffer, view.byteOffset, view.byteLength)
-            .set(new Uint8Array(chunk.buffer, chunk.byteOffset, bytesToCopy));
+      // Process any leftover data from previous read
+      const processLeftover = () => {
+        while (leftoverChunk) {
+          const byobRequest = controller.byobRequest;
+          if (byobRequest) {
+            const view = (controller.byobRequest as ReadableStreamBYOBRequest).view;
+            const bytesToCopy = Math.min(view.byteLength, leftoverChunk.length);
+
+            console.log(`[DEBUG] leftoverChunk length: ${leftoverChunk?.length}`);
+            console.log(`[DEBUG] BYOB request size: ${view.byteLength}`);
+
+            // Copy leftoverChunk into the BYOB buffer
+            new Uint8Array(view.buffer, view.byteOffset, bytesToCopy).set(
+              leftoverChunk.subarray(0, bytesToCopy)
+            );
+
+            (controller.byobRequest as ReadableStreamBYOBRequest).respond(bytesToCopy);
+
+            // Update leftoverChunk with unprocessed data
+            if (bytesToCopy < leftoverChunk.length) {
+              leftoverChunk = leftoverChunk.subarray(bytesToCopy);
+            } else {
+              leftoverChunk = null;
+            }
+          } else {
+            // No BYOB request, enqueue leftover data
+            controller.enqueue(leftoverChunk);
+            leftoverChunk = null;
+          }
+        }
 
-          (controller.byobRequest as ReadableStreamBYOBRequest).respond(bytesToCopy);
+        // If no leftoverChunk, resume Node.js stream
+        if (controller.desiredSize !== null && controller.desiredSize > 0 && nodeReadable.isPaused()) {
+          nodeReadable.resume();
+        }
+      };
 
-          if (bytesToCopy < chunk.byteLength) {
-            controller.enqueue(chunk.subarray(bytesToCopy));
-          }
+      const onData = (chunk: Buffer) => {
+        if (leftoverChunk) {
+          // Combine leftover data with new chunk
+          const combined = new Uint8Array(leftoverChunk.length + chunk.length);
+          combined.set(leftoverChunk);
+          combined.set(chunk, leftoverChunk.length);
+          leftoverChunk = combined;
         } else {
-          controller.enqueue(new Uint8Array(chunk));
+          leftoverChunk = new Uint8Array(chunk);
         }
+
+        processLeftover();  // Process leftover data immediately
       };
 
       const onEnd = () => {
+        if (leftoverChunk) {
+          controller.enqueue(leftoverChunk);
+          leftoverChunk = null;
+        }
         controller.close();
-        cleanup();
       };
 
       const onError = (err: Error) => {
         controller.error(err);
-        cleanup();
-      };
-
-      const cleanup = () => {
-        nodeReadable.off('data', onData);
-        nodeReadable.off('end', onEnd);
-        nodeReadable.off('error', onError);
       };
 
       nodeReadable.on('data', onData);
       nodeReadable.on('end', onEnd);
       nodeReadable.on('error', onError);
+
       nodeReadable.resume();
     },
-    pull(controller) {
-      if (nodeReadable.isPaused()) {
+    pull(controller: ReadableByteStreamController) {
+      // If there's leftover data, process it
+      if (leftoverChunk) {
+        const byobRequest = controller.byobRequest;
+        if (byobRequest) {
+          const view = (controller.byobRequest as ReadableStreamBYOBRequest).view;
+
+          const bytesToCopy = Math.min(view.byteLength, leftoverChunk.length);
+
+          new Uint8Array(view.buffer, view.byteOffset, bytesToCopy).set(
+            leftoverChunk.subarray(0, bytesToCopy)
+          );
+
+          (controller.byobRequest as ReadableStreamBYOBRequest).respond(bytesToCopy);
+
+          if (bytesToCopy < leftoverChunk.length) {
+            leftoverChunk = leftoverChunk.subarray(bytesToCopy);
+          } else {
+            leftoverChunk = null;
+          }
+        } else {
+          controller.enqueue(leftoverChunk);
+          leftoverChunk = null;
+        }
+      }
+
+      // Always resume the Node.js stream if paused
+      if (!leftoverChunk && nodeReadable.isPaused()) {
         nodeReadable.resume();
       }
     },
     cancel(reason) {
       nodeReadable.destroy(reason);
-    }
+    },
   });
 }