@Test public void txn_write_02() {

    long x = 
        Txn.calculateWrite(counter, () -> {
            counter.inc() ;
            assertEquals("In W, value()", 0, counter.value()) ;
            assertEquals("In W, get()",1, counter.get()) ;
            long z = counter.get() ;
            counter.abort() ;
            return z ;
        }) ;
    assertEquals("Outside W",1, x) ;
}