def test_kw_isub(self): P = self.rst_file["PRESSURE"][5] fipnum = self.init_file["FIPNUM"][0] fipnum_copy = fipnum.deep_copy() reg = EclRegion(self.grid, False) reg.select_more(P, 260) fipnum.sub(1, mask=reg) self.assertFalse(fipnum.equal(fipnum_copy)) fipnum.add(1, mask=reg) self.assertTrue(fipnum.equal(fipnum_copy))