diff --git a/CMakeLists.txt b/CMakeLists.txt
index 307bf2620a..e0504cb518 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -82,11 +82,16 @@ include(CMakeDependentOption)
 CMAKE_DEPENDENT_OPTION(ALL_TESTS "Build all tests" OFF "BUILD_TESTING;BUILD_CXX" OFF)
 message(STATUS "Build all tests: ${ALL_TESTS}")
 
-CMAKE_DEPENDENT_OPTION(BUILD_EXTRA_UNIT_TESTS "Build extra unit tests" OFF "BUILD_TESTING;BUILD_CXX;ALL_TESTS" OFF)
+CMAKE_DEPENDENT_OPTION(BUILD_EXTRA_UNIT_TESTS "Build extra unit tests" OFF "ALL_TESTS" OFF)
 if (BUILD_EXTRA_UNIT_TESTS)
   message(STATUS "Build extra unit tests: ON")
 endif()
 
+CMAKE_DEPENDENT_OPTION(BUILD_EXTRA_PROBLEM_SET "Build extra instance tests" OFF "BUILD_TESTING" OFF)
+if (BUILD_EXTRA_PROBLEM_SET)
+  message(STATUS "Build extra instance tests: ON")
+endif()
+
 option(ZLIB "ZLIB" ON)
 message(STATUS "ZLIB: ${ZLIB}")
 if (PYTHON_BUILD_SETUP)
diff --git a/check/CMakeLists.txt b/check/CMakeLists.txt
index 1da4017262..9aa5db34a4 100644
--- a/check/CMakeLists.txt
+++ b/check/CMakeLists.txt
@@ -86,14 +86,16 @@ if (NOT FAST_BUILD OR ALL_TESTS)
       set(TEST_SOURCES ${TEST_SOURCES} TestSpecialLps.cpp TestLpSolvers.cpp TestMipSolver.cpp)
   endif()
 
-  add_executable(unit_tests ${TEST_SOURCES})
+    if (BUILD_EXTRA_UNIT_TESTS)
+        list(APPEND CMAKE_MODULE_PATH "${HIGHS_SOURCE_DIR}/check/highs-unit-tests")
+        message(STATUS "${HIGHS_SOURCE_DIR}/check/highs-unit-tests")
+        include(highs-unit-tests)
 
-  if (BUILD_EXTRA_UNIT_TESTS)
-        list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/highs-unit-tests")
-        include(extra-tests)
-        message(STATUS "EXTRA TESTS: ${HIGHS_EXTRA_UNIT_TESTS}")
-        set(TEST_SOURCES ${HIGHS_EXTRA_UNIT_TESTS})
-  endif()
+        set(TEST_SOURCES ${TEST_SOURCES} ${HIGHS_EXTRA_UNIT_TESTS})
+        message(STATUS ${TEST_SOURCES})
+    endif()
+
+  add_executable(unit_tests ${TEST_SOURCES})
 
   if (UNIX)
       target_compile_options(unit_tests PRIVATE "-Wno-unused-variable")
@@ -331,3 +333,9 @@ if (NOT FAST_BUILD OR ALL_TESTS)
   endforeach()
 
 endif()
+
+if (BUILD_EXTRA_PROBLEM_SET)
+    list(APPEND CMAKE_MODULE_PATH "${HIGHS_SOURCE_DIR}/check/highs-problem-set")
+    message(STATUS "${HIGHS_SOURCE_DIR}/check/highs-problem-set")
+    include(highs-problem-set)
+endif()