MinusOpNode expr = new MinusOpNode();
expr.addChild(new IntegerNode(17));
DataRefNode dataRef = new DataRefNode(false, false, "boo");
expr.addChild(dataRef);
IncompleteEvalVisitor iev = new IncompleteEvalVisitor(ImmutableMap.of("boo", 13.0));
assertEquals(4.0, iev.exec(expr));
expr.replaceChild(0, new IntegerNode(34));