8.3. Using fake Streams in tests

Often we need to have a Fake InputStream or a Fake OutputStream, without having to generate a Stream fully in memory.

Example of usage of FakeInputStream VoidOutputStream in a test

  @Test
  void createConsumeInputOutputStream() {
     long length = x;
     try (InputStream inputStream = new FakeInputStream(length);  // Return a Fake InputStream with random content
          OutputStream outputStream = new VoidOutputStream()) {   // DevNull OutputStream
        assertEquals(length, inputStream.transferTo(outputStream));
     }
     try (InputStream inputStream = new FakeInputStream(length, (byte) 'A');  // Content will be fill with 'A'
          OutputStream outputStream = new VoidOutputStream()) {   // DevNull OutputStream
        assertEquals(length, inputStream.transferTo(outputStream));
     }
  }
}