text: #include <stan/math/prim/mat/meta/index_type.hpp>
  #include <test/unit/math/prim/scal/fun/promote_type_test_util.hpp>
  #include <gtest/gtest.h>
  
  TEST(MathMeta, index_type) {
    using Eigen::Matrix;
    using Eigen::Dynamic;
    using stan::math::index_type;
  
    expect_same_type<Matrix<double,Dynamic,Dynamic>::Index,
                     index_type<Matrix<double,Dynamic,Dynamic> >::type>();
  
    expect_same_type<Matrix<double,Dynamic,1>::Index,
                     index_type<Matrix<double,Dynamic,1> >::type>();
  
    expect_same_type<Matrix<double,1,Dynamic>::Index,
                     index_type<Matrix<double,1,Dynamic> >::type>();
  }
  