anchor.diff:  
       var bytesFromFile = await file.readAsBytes();
       Expect.listEquals(result, bytesFromFile);
  +
  +    await openedFile.close();
  +
       asyncTestDone("testWriteFrom");
     }
   
  
positive.code:     read(1, 3, 2, [null, 1, 2]);
      read(2, 3, 1, [null, null, 1]);
      read(0, 0, 0, [null, null, null]);
    }
  
    static testWriteFrom() async {
  
negative.code: 
      var bytesFromFile = file.readAsBytesSync();
      Expect.listEquals(result, bytesFromFile);
  
      openedFile.closeSync();
    }
  
    // Tests exception handling after file was closed.
  