text: #include <stan/math/rev/scal.hpp>
  #include <gtest/gtest.h>
  #include <limits>
  
  TEST(AgradRev, asBool) {
    using stan::math::as_bool;
    using stan::math::var;
  
    EXPECT_TRUE(as_bool(var(1)));
    EXPECT_TRUE(as_bool(var(-10L)));
    EXPECT_TRUE(as_bool(var(1.7)));
    EXPECT_TRUE(as_bool(var(-1.7)));
    EXPECT_TRUE(as_bool(var(std::numeric_limits<double>::infinity())));
    EXPECT_TRUE(as_bool(var(-std::numeric_limits<double>::infinity())));
    // don't like this behavior, but it's what C++ does
    EXPECT_TRUE(as_bool(var(std::numeric_limits<double>::quiet_NaN())));
  
    EXPECT_FALSE(as_bool(var(0)));
    EXPECT_FALSE(as_bool(var(0.0)));
    EXPECT_FALSE(as_bool(var(0.0f)));
  }
  TEST(AgradRev, as_bool_nan) {
    stan::math::var nan = std::numeric_limits<double>::quiet_NaN();
    EXPECT_TRUE(stan::math::as_bool(nan));
  }
  