diff --git a/.github/workflows/cmake.yml b/.github/workflows/cmake.yml
index 5ddd91ead..71f2ed6f3 100644
--- a/.github/workflows/cmake.yml
+++ b/.github/workflows/cmake.yml
@@ -15,9 +15,11 @@ jobs:
           - os: ubuntu-22.04
             cc: /usr/bin/gcc-12
             cxx: /usr/bin/g++-12
+            env: MPIEXEC=/usr/bin/mpiexec
           - os: macos-latest
             cc: clang
             cxx: clang++
+            env: MPIEXEC=/opt/homebrew/bin/mpiexec
 
     name: "${{ matrix.os }}: ${{ matrix.cxx }} ${{ matrix.build_type }}"
     runs-on: ${{ matrix.os }}
@@ -112,11 +114,11 @@ jobs:
       run: |
         cmake -S $GITHUB_WORKSPACE/doc/dox/dev/devsamp/helloworld -B test_install_devsamp_helloworld -DCMAKE_PREFIX_PATH=${{github.workspace}}/install || (cat test_install_devsamp_helloworld/CMakeFiles/CMakeOutput.log && cat test_install_devsamp_helloworld/CMakeFiles/CMakeError.log)
         cmake --build test_install_devsamp_helloworld
-        test_install_devsamp_helloworld/helloworld-parsec
-        test_install_devsamp_helloworld/helloworld-mad
+        ${MPIEXEC} -n 2 test_install_devsamp_helloworld/helloworld-parsec
+        ${MPIEXEC} -n 2 test_install_devsamp_helloworld/helloworld-mad
         cmake -S $GITHUB_WORKSPACE/doc/dox/dev/devsamp/fibonacci -B test_install_devsamp_fibonacci -DCMAKE_PREFIX_PATH=${{github.workspace}}/install || (cat test_install_devsamp_fibonacci/CMakeFiles/CMakeOutput.log && cat test_install_devsamp_fibonacci/CMakeFiles/CMakeError.log)
         cmake --build test_install_devsamp_fibonacci
-        test_install_devsamp_fibonacci/fibonacci-parsec
+        ${MPIEXEC} -n 2 test_install_devsamp_fibonacci/fibonacci-parsec
         cmake -E make_directory test_install_userexamples
         cat > test_install_userexamples/CMakeLists.txt <<EOF
         cmake_minimum_required(VERSION 3.14)