diff --git a/lib/sundials_6.1.1/lib/stlTVNfQ b/lib/sundials_6.1.1/lib/stlTVNfQ
new file mode 100644
index 00000000000..e69de29bb2d
diff --git a/lib/sundials_6.1.1/lib/stytHoFH b/lib/sundials_6.1.1/lib/stytHoFH
new file mode 100644
index 00000000000..e69de29bb2d
diff --git a/test/unit/math/mix/functor/reduce_sum_part1_test.cpp b/test/unit/math/mix/functor/reduce_sum_part1_test.cpp
index abf7bc184f3..446aeaf7c33 100644
--- a/test/unit/math/mix/functor/reduce_sum_part1_test.cpp
+++ b/test/unit/math/mix/functor/reduce_sum_part1_test.cpp
@@ -1,14 +1,14 @@
 #include <stan/math/prim/meta.hpp>
 #include <test/unit/math/test_ad.hpp>
 #include <test/unit/math/mix/functor/reduce_sum_util.hpp>
-
+#include <test/unit/math/rev/util.hpp>
 #include <limits>
 #include <vector>
 
 // Reduce sum tests are broken up into four files to avoid windows compiler
 // error
 
-TEST(MathMix_reduce_sum, grainsize_static) {
+TEST_F(AgradRev, reduce_sum_grainsize_static) {
   using stan::math::test::get_new_msg;
   using stan::math::test::sum_lpdf;
 
@@ -33,7 +33,7 @@ TEST(MathMix_reduce_sum, grainsize_static) {
   stan::test::expect_ad(f4, data);
 }
 
-TEST(MathMix_reduce_sum, grainsize) {
+TEST_F(AgradRev, reduce_sum_grainsize) {
   using stan::math::test::get_new_msg;
   using stan::math::test::sum_lpdf;
   auto f1 = [](auto&& data) {
@@ -57,7 +57,7 @@ TEST(MathMix_reduce_sum, grainsize) {
   stan::test::expect_ad(f4, data);
 }
 
-TEST(MathMix_reduce_sum, std_vector_zero_length) {
+TEST_F(AgradRev, reduce_sum_std_vector_zero_length) {
   using stan::math::test::reduce_sum_static_sum_lpdf;
   using stan::math::test::reduce_sum_sum_lpdf;
 
@@ -67,7 +67,7 @@ TEST(MathMix_reduce_sum, std_vector_zero_length) {
   stan::test::expect_ad(reduce_sum_sum_lpdf, data);
 }
 
-TEST(MathMix_reduce_sum, std_vector_double_slice) {
+TEST_F(AgradRev, reduce_sum_std_vector_double_slice) {
   using stan::math::test::reduce_sum_static_sum_lpdf;
   using stan::math::test::reduce_sum_sum_lpdf;
 
@@ -77,7 +77,7 @@ TEST(MathMix_reduce_sum, std_vector_double_slice) {
   stan::test::expect_ad(reduce_sum_sum_lpdf, data);
 }
 
-TEST(MathMix_reduce_sum, std_vector_std_vector_double_slice) {
+TEST_F(AgradRev, reduce_sum_std_vector_std_vector_double_slice) {
   using stan::math::test::reduce_sum_static_sum_lpdf;
   using stan::math::test::reduce_sum_sum_lpdf;
 
@@ -87,7 +87,7 @@ TEST(MathMix_reduce_sum, std_vector_std_vector_double_slice) {
   stan::test::expect_ad(reduce_sum_sum_lpdf, data);
 }
 
-TEST(MathMix_reduce_sum, std_vector_eigen_vector_double_slice) {
+TEST_F(AgradRev, reduce_sum_std_vector_eigen_vector_double_slice) {
   using stan::math::test::reduce_sum_static_sum_lpdf;
   using stan::math::test::reduce_sum_sum_lpdf;
 
@@ -97,7 +97,7 @@ TEST(MathMix_reduce_sum, std_vector_eigen_vector_double_slice) {
   stan::test::expect_ad(reduce_sum_sum_lpdf, data);
 }
 
-TEST(MathMix_reduce_sum, std_vector_eigen_row_vector_double_slice) {
+TEST_F(AgradRev, reduce_sum_std_vector_eigen_row_vector_double_slice) {
   using stan::math::test::reduce_sum_static_sum_lpdf;
   using stan::math::test::reduce_sum_sum_lpdf;
 
@@ -107,7 +107,7 @@ TEST(MathMix_reduce_sum, std_vector_eigen_row_vector_double_slice) {
   stan::test::expect_ad(reduce_sum_sum_lpdf, data);
 }
 
-TEST(MathMix_reduce_sum, std_vector_eigen_matrix_double_slice) {
+TEST_F(AgradRev, reduce_sum_std_vector_eigen_matrix_double_slice) {
   using stan::math::test::reduce_sum_static_sum_lpdf;
   using stan::math::test::reduce_sum_sum_lpdf;
 
@@ -117,7 +117,7 @@ TEST(MathMix_reduce_sum, std_vector_eigen_matrix_double_slice) {
   stan::test::expect_ad(reduce_sum_sum_lpdf, data);
 }
 
-TEST(MathMix_reduce_sum, std_vector_std_vector_std_vector_double_slice) {
+TEST_F(AgradRev, reduce_sum_std_vector_std_vector_std_vector_double_slice) {
   using stan::math::test::reduce_sum_static_sum_lpdf;
   using stan::math::test::reduce_sum_sum_lpdf;
 
@@ -128,7 +128,7 @@ TEST(MathMix_reduce_sum, std_vector_std_vector_std_vector_double_slice) {
   stan::test::expect_ad(reduce_sum_sum_lpdf, data);
 }
 
-TEST(MathMix_reduce_sum, std_vector_std_vector_eigen_vector_double_slice) {
+TEST_F(AgradRev, reduce_sum_std_vector_std_vector_eigen_vector_double_slice) {
   using stan::math::test::reduce_sum_static_sum_lpdf;
   using stan::math::test::reduce_sum_sum_lpdf;
 
@@ -139,7 +139,7 @@ TEST(MathMix_reduce_sum, std_vector_std_vector_eigen_vector_double_slice) {
   stan::test::expect_ad(reduce_sum_sum_lpdf, data);
 }
 
-TEST(MathMix_reduce_sum, std_vector_std_vector_eigen_row_vector_double_slice) {
+TEST_F(AgradRev, reduce_sum_std_vector_std_vector_eigen_row_vector_double_slice) {
   using stan::math::test::reduce_sum_static_sum_lpdf;
   using stan::math::test::reduce_sum_sum_lpdf;
 
@@ -150,7 +150,7 @@ TEST(MathMix_reduce_sum, std_vector_std_vector_eigen_row_vector_double_slice) {
   stan::test::expect_ad(reduce_sum_sum_lpdf, data);
 }
 
-TEST(MathMix_reduce_sum, std_vector_std_vector_eigen_matrix_double_slice) {
+TEST_F(AgradRev, reduce_sum_std_vector_std_vector_eigen_matrix_double_slice) {
   using stan::math::test::reduce_sum_static_sum_lpdf;
   using stan::math::test::reduce_sum_sum_lpdf;
 
@@ -180,7 +180,7 @@ TEST(StanMath_reduce_sum_static, start_end_slice) {
   stan::test::expect_ad(start_end_static, data);
 }
 
-TEST(MathMix_reduce_sum, int_arg) {
+TEST_F(AgradRev, reduce_sum_int_arg) {
   using stan::math::test::reduce_sum_static_sum_lpdf;
   using stan::math::test::reduce_sum_sum_lpdf;
   std::vector<double> data(2, 1.0);
@@ -192,7 +192,7 @@ TEST(MathMix_reduce_sum, int_arg) {
       [&](auto&& data) { return reduce_sum_sum_lpdf(data, arg); }, data);
 }
 
-TEST(MathMix_reduce_sum, std_vector_int_arg) {
+TEST_F(AgradRev, reduce_sum_std_vector_int_arg) {
   using stan::math::test::reduce_sum_static_sum_lpdf;
   using stan::math::test::reduce_sum_sum_lpdf;
   std::vector<double> data(2, 10.0);
@@ -204,12 +204,12 @@ TEST(MathMix_reduce_sum, std_vector_int_arg) {
       [&](auto&& data) { return reduce_sum_sum_lpdf(data, arg); }, data);
 }
 
-TEST(MathMix_reduce_sum, double_arg) {
+TEST_F(AgradRev, reduce_sum_double_arg) {
   stan::math::test::expect_ad_reduce_sum_lpdf(std::vector<double>(2, 10.0),
                                               5.0);
 }
 
-TEST(MathMix_reduce_sum, std_vector_double_arg) {
+TEST_F(AgradRev, reduce_sum_std_vector_double_arg) {
   stan::math::test::expect_ad_reduce_sum_lpdf(std::vector<double>(2, 10.0),
                                               std::vector<double>(2, 10.0));
 }
diff --git a/test/unit/math/mix/functor/reduce_sum_part2_test.cpp b/test/unit/math/mix/functor/reduce_sum_part2_test.cpp
index 524671b3223..16a9c7b4b2d 100644
--- a/test/unit/math/mix/functor/reduce_sum_part2_test.cpp
+++ b/test/unit/math/mix/functor/reduce_sum_part2_test.cpp
@@ -1,6 +1,7 @@
 #include <stan/math/prim/meta.hpp>
 #include <test/unit/math/test_ad.hpp>
 #include <test/unit/math/mix/functor/reduce_sum_util.hpp>
+#include <test/unit/math/rev/util.hpp>
 
 #include <limits>
 #include <vector>
@@ -8,41 +9,41 @@
 // Reduce sum tests are broken up into four files to avoid windows compiler
 // error
 
-TEST(MathMix_reduce_sum, eigen_vector_arg) {
+TEST_F(AgradRev, reduce_sum_eigen_vector_arg) {
   std::vector<double> data(2, 10.0);
   Eigen::VectorXd arg = Eigen::VectorXd::Ones(2);
   stan::math::test::expect_ad_reduce_sum_lpdf(data, arg);
 }
 
-TEST(MathMix_reduce_sum, eigen_row_vector_arg) {
+TEST_F(AgradRev, reduce_sum_eigen_row_vector_arg) {
   std::vector<double> data(2, 10.0);
   Eigen::RowVectorXd arg = Eigen::RowVectorXd::Ones(2);
 
   stan::math::test::expect_ad_reduce_sum_lpdf(data, arg);
 }
 
-TEST(MathMix_reduce_sum, eigen_matrix_arg) {
+TEST_F(AgradRev, reduce_sum_eigen_matrix_arg) {
   std::vector<double> data(2, 10.0);
   Eigen::MatrixXd arg = Eigen::MatrixXd::Ones(2, 2);
 
   stan::math::test::expect_ad_reduce_sum_lpdf(data, arg);
 }
 
-TEST(MathMix_reduce_sum, std_vector_std_vector_double_arg) {
+TEST_F(AgradRev, reduce_sum_std_vector_std_vector_double_arg) {
   std::vector<double> data(2, 10.0);
   std::vector<std::vector<double>> arg(2, std::vector<double>(2, 10.0));
 
   stan::math::test::expect_ad_reduce_sum_lpdf(data, arg);
 }
 
-TEST(MathMix_reduce_sum, std_vector_eigen_vector_arg) {
+TEST_F(AgradRev, reduce_sum_std_vector_eigen_vector_arg) {
   std::vector<double> data(2, 10.0);
   std::vector<Eigen::VectorXd> arg(2, Eigen::VectorXd::Ones(2));
 
   stan::math::test::expect_ad_reduce_sum_lpdf(data, arg);
 }
 
-TEST(MathMix_reduce_sum, std_vector_eigen_row_vector_arg) {
+TEST_F(AgradRev, reduce_sum_std_vector_eigen_row_vector_arg) {
   std::vector<double> data(2, 10.0);
   std::vector<Eigen::RowVectorXd> arg(2, Eigen::RowVectorXd::Ones(2));
 
diff --git a/test/unit/math/mix/functor/reduce_sum_part3_test.cpp b/test/unit/math/mix/functor/reduce_sum_part3_test.cpp
index 52723cdeee3..1999ce0d871 100644
--- a/test/unit/math/mix/functor/reduce_sum_part3_test.cpp
+++ b/test/unit/math/mix/functor/reduce_sum_part3_test.cpp
@@ -1,6 +1,7 @@
 #include <stan/math/prim/meta.hpp>
 #include <test/unit/math/test_ad.hpp>
 #include <test/unit/math/mix/functor/reduce_sum_util.hpp>
+#include <test/unit/math/rev/util.hpp>
 
 #include <limits>
 #include <vector>
@@ -8,7 +9,7 @@
 // Reduce sum tests are broken up into four files to avoid windows compiler
 // error
 
-TEST(MathMix_reduce_sum, eigen_three_args1) {
+TEST_F(AgradRev, reduce_sum_eigen_three_args1) {
   using stan::math::test::reduce_sum_int_sum_lpdf;
   using stan::math::test::reduce_sum_static_int_sum_lpdf;
   Eigen::VectorXd arg1 = Eigen::VectorXd::Ones(2);
@@ -19,7 +20,7 @@ TEST(MathMix_reduce_sum, eigen_three_args1) {
   stan::test::expect_ad(reduce_sum_int_sum_lpdf, arg1, arg2, arg3);
 }
 
-TEST(MathMix_reduce_sum, eigen_three_args2) {
+TEST_F(AgradRev, reduce_sum_eigen_three_args2) {
   using stan::math::test::reduce_sum_int_sum_lpdf;
   using stan::math::test::reduce_sum_static_int_sum_lpdf;
   double arg1 = 1.0;
@@ -30,7 +31,7 @@ TEST(MathMix_reduce_sum, eigen_three_args2) {
   stan::test::expect_ad(reduce_sum_int_sum_lpdf, arg1, arg2, arg3);
 }
 
-TEST(MathMix_reduce_sum, eigen_three_args3) {
+TEST_F(AgradRev, reduce_sum_eigen_three_args3) {
   using stan::math::test::reduce_sum_int_sum_lpdf;
   using stan::math::test::reduce_sum_static_int_sum_lpdf;
   double arg1 = 1.0;
@@ -41,7 +42,7 @@ TEST(MathMix_reduce_sum, eigen_three_args3) {
   stan::test::expect_ad(reduce_sum_int_sum_lpdf, arg1, arg2, arg3);
 }
 
-TEST(MathMix_reduce_sum, eigen_three_args_with_ints1) {
+TEST_F(AgradRev, reduce_sum_eigen_three_args_with_ints1) {
   using stan::math::test::reduce_sum_int_sum_lpdf;
   using stan::math::test::reduce_sum_static_int_sum_lpdf;
   Eigen::VectorXd arg1 = Eigen::VectorXd::Ones(2);
@@ -63,7 +64,7 @@ TEST(MathMix_reduce_sum, eigen_three_args_with_ints1) {
       arg1, arg2, arg3);
 }
 
-TEST(MathMix_reduce_sum, eigen_three_args_with_ints2) {
+TEST_F(AgradRev, reduce_sum_eigen_three_args_with_ints2) {
   using stan::math::test::reduce_sum_int_sum_lpdf;
   using stan::math::test::reduce_sum_static_int_sum_lpdf;
   double arg1 = 1.0;
diff --git a/test/unit/math/mix/functor/reduce_sum_part4_test.cpp b/test/unit/math/mix/functor/reduce_sum_part4_test.cpp
index e2cfead9893..95d7ccf2fa7 100644
--- a/test/unit/math/mix/functor/reduce_sum_part4_test.cpp
+++ b/test/unit/math/mix/functor/reduce_sum_part4_test.cpp
@@ -1,6 +1,7 @@
 #include <stan/math/prim/meta.hpp>
 #include <test/unit/math/test_ad.hpp>
 #include <test/unit/math/mix/functor/reduce_sum_util.hpp>
+#include <test/unit/math/rev/util.hpp>
 
 #include <limits>
 #include <vector>
@@ -8,7 +9,7 @@
 // Reduce sum tests are broken up into four files to avoid windows compiler
 // error
 
-TEST(MathMix_reduce_sum, eigen_three_args_with_ints3) {
+TEST_F(AgradRev, reduce_sum_eigen_three_args_with_ints3) {
   using stan::math::test::reduce_sum_int_sum_lpdf;
   using stan::math::test::reduce_sum_static_int_sum_lpdf;
   double arg1 = 1.0;
@@ -30,7 +31,7 @@ TEST(MathMix_reduce_sum, eigen_three_args_with_ints3) {
       arg1, arg2, arg3);
 }
 
-TEST(MathMix_reduce_sum, eigen_three_args_with_doubles1) {
+TEST_F(AgradRev, reduce_sum_eigen_three_args_with_doubles1) {
   using stan::math::test::reduce_sum_static_sum_lpdf;
   using stan::math::test::reduce_sum_sum_lpdf;
   Eigen::VectorXd arg1 = Eigen::VectorXd::Ones(2);
@@ -53,7 +54,7 @@ TEST(MathMix_reduce_sum, eigen_three_args_with_doubles1) {
       arg1, arg2, arg3);
 }
 
-TEST(MathMix_reduce_sum, eigen_three_args_with_doubles2) {
+TEST_F(AgradRev, reduce_sum_eigen_three_args_with_doubles2) {
   using stan::math::test::reduce_sum_static_sum_lpdf;
   using stan::math::test::reduce_sum_sum_lpdf;
   double arg1 = 1.0;
@@ -77,7 +78,7 @@ TEST(MathMix_reduce_sum, eigen_three_args_with_doubles2) {
       arg1, arg2, arg3);
 }
 
-TEST(MathMix_reduce_sum, eigen_three_args_with_doubles3) {
+TEST_F(AgradRev, reduce_sum_eigen_three_args_with_doubles3) {
   using stan::math::test::reduce_sum_static_sum_lpdf;
   using stan::math::test::reduce_sum_sum_lpdf;
   double arg1 = 1.0;
@@ -102,7 +103,7 @@ TEST(MathMix_reduce_sum, eigen_three_args_with_doubles3) {
 }
 
 #ifdef STAN_THREADS
-TEST(MathMix_reduce_sum, static_check) {
+TEST_F(AgradRev, reduce_sum_static_check) {
   using stan::math::test::get_new_msg;
   using stan::math::test::static_check_lpdf;