INode node = getInstance(getA(0));
ValueNode<Double> res = node.calc(null);
assertTrue(res.getValue().compareTo(Math.sqrt(1)) == 0);
node = getInstance(getA(1));
res = node.calc(null);
assertTrue(res.getValue().compareTo(Math.sqrt(36)) == 0);
node = getInstance(getA(2));
res = node.calc(null);
assertTrue(res.getValue().compareTo(Math.sqrt(0)) == 0);