@Test
public void testLinear() {

    Day start=Day.toDay();
    TsDomain domain=new TsDomain(new TsPeriod(TsFrequency.Monthly, start), 120);
    DataBlock data0=new DataBlock(domain.getLength());
    DataBlock data1=new DataBlock(domain.getLength());
    DiffConstant dc=new DiffConstant(new BackFilter(UnitRoots.D1), start);
    LinearTrend t=new LinearTrend(start);
    dc.data(domain.getStart(), data0);
    t.data(domain.getStart(), data1);
    assertTrue(data0.distance(data1)<1e-9);
}