add test for Buffer edge case

js/buffer.ts

@@ -132,8 +132,7 @@ export class Buffer implements Reader, Writer {
       // Buffer is empty, reset to recover space.
       this.reset();
       if (p.byteLength === 0) {
-        // TODO This edge case should be tested by porting TestReadEmptyAtEOF
-        // from the Go tests.
+        // this edge case is tested in 'bufferReadEmptyAtEOF' test
         return { nread: 0, eof: false };
       }
       return { nread: 0, eof: true };

js/buffer_test.ts

@@ -109,6 +109,16 @@ test(async function bufferBasicOperations() {
   }
 });
 
+test(async function bufferReadEmptyAtEOF() {
+  // check that EOF of 'buf' is not reached (even though it's empty) if
+  // results are written to buffer that has 0 length (ie. it can't store any data)
+  let buf = new Buffer();
+  const zeroLengthTmp = new Uint8Array(0);
+  let result = await buf.read(zeroLengthTmp);
+  assertEqual(result.nread, 0);
+  assertEqual(result.eof, false);
+});
+
 test(async function bufferLargeByteWrites() {
   init();
   const buf = new Buffer();