text: // Arguments: Doubles, Doubles
  #include <stan/math/prim.hpp>
  
  using stan::math::var;
  using std::numeric_limits;
  using std::vector;
  
  class AgradCdfInvChiSquare : public AgradCdfTest {
   public:
    void valid_values(vector<vector<double> >& parameters, vector<double>& cdf) {
      vector<double> param(2);
  
      param[0] = 3.0;  // y
      param[1] = 0.5;  // Degrees of freedom
      parameters.push_back(param);
      cdf.push_back(0.317528038297796704186230);  // expected cdf
    }
  
    void invalid_values(vector<size_t>& index, vector<double>& value) {
      // y
      index.push_back(0U);
      value.push_back(-1.0);
  
      // nu
      index.push_back(1U);
      value.push_back(-1.0);
  
      index.push_back(1U);
      value.push_back(0.0);
  
      index.push_back(1U);
      value.push_back(numeric_limits<double>::infinity());
    }
  
    bool has_lower_bound() { return true; }
  
    double lower_bound() { return 0.0; }
  
    bool has_upper_bound() { return false; }
  
    template <typename T_y, typename T_dof, typename T2, typename T3, typename T4,
              typename T5>
    stan::return_type_t<T_y, T_dof> cdf(const T_y& y, const T_dof& nu, const T2&,
                                        const T3&, const T4&, const T5&) {
      return stan::math::inv_chi_square_cdf(y, nu);
    }
  
    template <typename T_y, typename T_dof, typename T2, typename T3, typename T4,
              typename T5>
    stan::return_type_t<T_y, T_dof> cdf_function(const T_y& y, const T_dof& nu,
                                                 const T2&, const T3&, const T4&,
                                                 const T5&) {
      using stan::math::gamma_q;
  
      return gamma_q(0.5 * nu, 0.5 / y);
    }
  };
  