another file read problem [solved]

I do not seem to be able to read a file after opening it - what am I doing wrong?

const Storage = require('Storage');
  function compareFileWith (expectedContent) {
    if (''+Storage.read('4testing') !== expectedContent) {
      print('>>>> file does not look as expected');
      print('>>>> expected "' + expectedContent + '"');
      print('>>>> got "' + Storage.read('4testing') + '"');
    }
  }

/**** create file ****/

  if (Storage.write('4testing','Hello, World!')) {
    print('file "4testing" was successfully created');
  } else {
    print('file "4testing" could not be created');
  }
  compareFileWith('Hello, World!');

  let TestFile;

/**** read file ****/

  TestFile = Storage.open('4testing','r');

  let readText = TestFile.read(4);
  if (readText !== 'Hello') {
    print('>>>> reading "4testing" failed');
    print('>>>> expected "Hello", got "' + readText + '"');
  }

readText turns out to be undefined