diff --git a/CMakeLists.txt b/CMakeLists.txt
index c2db988..30cc645 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -5,6 +5,7 @@ project(hpc_stencil_demo LANGUAGES CXX)
 option(ENABLE_MPI "Build MPI executable" ON)
 option(ENABLE_TESTS "Build tests" ON)
 option(ENABLE_BENCHMARKS "Enable benchmark CTest labels" ON)
+option(ENABLE_MPI_OVERSUBSCRIBE "Allow MPI tests to oversubscribe small CI runners" ON)
 
 set(CMAKE_CXX_STANDARD 17)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
@@ -49,11 +50,32 @@ if(ENABLE_TESTS)
   add_test(NAME stencil_unit_tests COMMAND stencil_unit_tests)
 
   if(ENABLE_MPI)
-    add_test(NAME stencil_mpi_smoke COMMAND ${MPIEXEC_EXECUTABLE} ${MPIEXEC_NUMPROC_FLAG} 2 $<TARGET_FILE:stencil_mpi> --size 1000 --steps 20)
+    set(HPC_DEMO_MPIEXEC_PREFLAGS "")
+    if(ENABLE_MPI_OVERSUBSCRIBE)
+      list(APPEND HPC_DEMO_MPIEXEC_PREFLAGS "--oversubscribe")
+    endif()
+
+    function(add_hpc_demo_mpi_test test_name ranks)
+      add_test(
+        NAME ${test_name}
+        COMMAND
+          ${MPIEXEC_EXECUTABLE}
+          ${MPIEXEC_NUMPROC_FLAG} ${ranks}
+          ${HPC_DEMO_MPIEXEC_PREFLAGS}
+          $<TARGET_FILE:stencil_mpi>
+          ${ARGN}
+      )
+      set_tests_properties(${test_name}
+        PROPERTIES
+          ENVIRONMENT "OMPI_ALLOW_RUN_AS_ROOT=1;OMPI_ALLOW_RUN_AS_ROOT_CONFIRM=1"
+      )
+    endfunction()
+
+    add_hpc_demo_mpi_test(stencil_mpi_smoke 2 --size 1000 --steps 20)
   endif()
 
   if(ENABLE_BENCHMARKS AND ENABLE_MPI)
-    add_test(NAME benchmark_stencil_mpi COMMAND ${MPIEXEC_EXECUTABLE} ${MPIEXEC_NUMPROC_FLAG} 4 $<TARGET_FILE:stencil_mpi> --size 200000 --steps 200)
+    add_hpc_demo_mpi_test(benchmark_stencil_mpi 4 --size 200000 --steps 200)
     set_tests_properties(benchmark_stencil_mpi PROPERTIES LABELS benchmark)
   endif()
 endif()
@@ -68,4 +90,3 @@ if(ENABLE_MPI)
 endif()
 
 install(DIRECTORY include/ DESTINATION include)
-