diff --git a/.github/workflows/SampleFlow-test.yml b/.github/workflows/SampleFlow-test.yml
index eb7a422..7a7e7a5 100644
--- a/.github/workflows/SampleFlow-test.yml
+++ b/.github/workflows/SampleFlow-test.yml
@@ -18,7 +18,7 @@ jobs:
       run: |
         pushd .
         cd $HOME
-        sudo apt-get install -y doxygen graphviz libboost-all-dev numdiff clang libc++-dev libc++abi-dev libeigen3-dev
+        sudo apt-get install -y doxygen graphviz libboost-all-dev numdiff clang libc++-dev libc++abi-dev libeigen3-dev ninja-build
         doxygen --version
         popd
     - name: cmake-gcc
@@ -35,10 +35,11 @@ jobs:
            mkdir build-clang
            cd build-clang
            export CXX=clang++
-           cmake -DCMAKE_BUILD_TYPE=Debug ..
+           cmake -DCMAKE_BUILD_TYPE=Debug -GNinja ..
     - name: ctest-clang
       run: |
            cd build-clang
+           ninja
            ctest --output-on-failure -j2
     - name: doc
       run: |