diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index bcd47820..5c583e12 100755
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -14,14 +14,48 @@ jobs:
       #  newest: lts-19
       #  oldest: lts-18
     steps:
+#      - name: Clone project
+#        uses: actions/checkout@v4
+#      - name: Install LLVM 12
+#        if: job.name == macos-latest-llvm@12
+#        shell: bash
+#        run: |
+#          set -ex
+#          brew install llvm@12
+#          echo "/opt/homebrew/opt/llvm@12/bin" >> "${GITHUB_PATH}"
+#          echo LDFLAGS="-L/opt/homebrew/opt/llvm@12/lib" >> "${GITHUB_ENV}"
+#          echo CPPFLAGS="-I/opt/homebrew/opt/llvm@12/include" >> "${GITHUB_ENV}"
+#      - name: Setup Haskell
+#        uses: haskell-actions/setup@v2.7.5
+#        with:
+#          enable-stack: true
+#          stack-version: 'latest'
+#          stack-no-global: true
+#          cabal-update: false
+#      - name: Install stack-all
+#        shell: bash
+#        run: |
+#          set -ex
+#          stack --version
+#          stack install stack-all
+#          stack-all --version
+#      - name: Build and run tests
+#        shell: bash
+#        run: |
+#          set -ex
+#          stack-all --oldest lts-18 --newest lts-19
+
       - name: Clone project
-        uses: actions/checkout@v4
+        uses: actions/checkout@v2
       - name: Install LLVM 12
-        if: job.name == macos-latest-llvm@12
         shell: bash
         run: |
           set -ex
+          echo "$(brew --prefix)"
           brew install llvm@12
+          ls -F "$(brew --prefix)"
+          ls -F "$(brew --prefix)/opt"
+          ls -F "$(brew --prefix)/opt/llvm@12"
           echo "/opt/homebrew/opt/llvm@12/bin" >> "${GITHUB_PATH}"
           echo LDFLAGS="-L/opt/homebrew/opt/llvm@12/lib" >> "${GITHUB_ENV}"
           echo CPPFLAGS="-I/opt/homebrew/opt/llvm@12/include" >> "${GITHUB_ENV}"
@@ -32,18 +66,13 @@ jobs:
           stack-version: 'latest'
           stack-no-global: true
           cabal-update: false
-      - name: Install stack-all
-        shell: bash
-        run: |
-          set -ex
-          stack --version
-          stack install stack-all
-          stack-all --version
       - name: Build and run tests
         shell: bash
         run: |
-          set -ex
-          stack-all --oldest lts-18 --newest lts-19
+            set -ex
+            echo $PATH
+            stack --version
+            stack test --fast --no-terminal --stack-yaml=${{ matrix.stack-yaml }} --resolver=${{ matrix.resolver }}
 
 #  macos-13:
 #    name: macos-13