@Test
@PrepareForTest({FileOutputStream.class, SingleWriterMultipleReaderFile.class})

public void testStartWrite_success() throws Exception {
    when(reader.startWrite()).thenCallRealMethod();
    when(workFile.exists()).thenReturn(false);
    when(workFile.getPath()).thenReturn("/nonexisting/path/for/dns66");
    whenNew(FileOutputStream.class).withAnyArguments().thenReturn(fos);
    assertSame(fos, reader.startWrite());
}