public void NegativeInteger_Integer_CorrectNegativeValue(int input, int expected) { IntegerLiteralExpression intLitExpr = new IntegerLiteralExpression(input, 0, 0); NegativeExpression negExpr = new NegativeExpression(new List <ExpressionNode>() { intLitExpr }, 0, 0); IInterpreterInteger parent = Substitute.For <IInterpreterInteger>(); parent.DispatchInt(intLitExpr, Arg.Any <List <object> >()).Returns(input); IntegerHelper integerHelper = SetUpHelper(parent); double res = integerHelper.NegativeInteger(negExpr, new List <object>()); Assert.AreEqual(expected, res); }