public void AstShiftTest2() {
AstRoot ast = RParser.Parse(new TextStream(" a()"));
var scope = ast.Children[0].Should().BeAssignableTo<IScope>().Which;
scope.Children[0].Start.Should().Be(1);
var expression = scope.Children[0].Should().BeAssignableTo<IStatement>()
.Which.Children[0].Should().BeAssignableTo<IExpression>()
.Which;
expression.Children[0].Start.Should().Be(1);
var func = expression.Children[0].Should().BeAssignableTo<IFunction>()
.Which;
func.OpenBrace.Start.Should().Be(2);
ast.ShiftStartingFrom(2, 1);
func.OpenBrace.Start.Should().Be(3);
}