@Test
public void testCreateInputStream() throws IOException, B2Exception {

    final InputStream underlyingStream = new ByteArrayInputStream(new byte[0]);
    when(source.createInputStream()).thenReturn(underlyingStream);
    final InputStream wrappedStream = partOf.createInputStream();
    assertTrue(wrappedStream instanceof B2InputStreamExcerpt);
    final B2InputStreamExcerpt excerpt = (B2InputStreamExcerpt) wrappedStream;
    assertEquals(26, excerpt.getExcerptStart());
    assertEquals(100, excerpt.getExcerptLength());
}