diff --git a/.github/actions/setup/macos/action.yml b/.github/actions/setup/macos/action.yml
new file mode 100644
index 0000000..75147e9
--- /dev/null
+++ b/.github/actions/setup/macos/action.yml
@@ -0,0 +1,37 @@
+name: Setup macOS environment
+description: >-
+  Installs necessary packages via Homebrew.
+
+inputs: {} # nothing?
+
+outputs: {} # nothing?
+
+runs:
+  using: composite
+
+  steps:
+    - name: brew
+      shell: bash
+      run: |
+        brew install --quiet gmp libffi openssl@3 zlib autoconf automake libtool
+
+    - name: Set ENV
+      shell: bash
+      run: |
+        dir_config() {
+          local args=() lib var="$1"; shift
+          for lib in "$@"; do
+            args+="--with-${lib%@*}-dir=$(brew --prefix $lib)"
+          done
+          echo "$var=${args[*]}" >> $GITHUB_ENV
+        }
+        dir_config ruby_configure_args gmp
+        dir_config CONFIGURE_ARGS openssl@3
+
+    - name: make sure that kern.coredump=1
+      shell: bash
+      run: |
+        sysctl -n kern.coredump
+        sudo sysctl -w kern.coredump=1
+        sudo chmod -R +rwx /cores/
+
diff --git a/.github/actions/setup/ubuntu/action.yml b/.github/actions/setup/ubuntu/action.yml
new file mode 100644
index 0000000..ddf7870
--- /dev/null
+++ b/.github/actions/setup/ubuntu/action.yml
@@ -0,0 +1,58 @@
+name: Setup ubuntu environment
+description: >-
+  At the beginning there was no way but to copy & paste `apt-get`
+  everywhere.  But now that we have composite actions, it seems better
+  merge them into one.
+
+inputs:
+  arch:
+    required: false
+    default: ''
+    description: >-
+      Architecture.  Because we run this on a GitHub-hosted runner
+      acceptable value for this input is very limited.
+
+outputs:
+  arch:
+    value: ${{ steps.uname.outputs.uname }}
+    description: >-
+      Actual architecture.  This could be different from the one
+      passed to the `inputs.arch`.  For instance giving `i386` to this
+      action yields `i686`.
+
+runs:
+  using: composite
+
+  steps:
+    - name: set SETARCH
+      shell: bash
+      run: echo "SETARCH=${setarch}" >> "$GITHUB_ENV"
+      env:
+        setarch: ${{ inputs.arch && format('setarch {0} --', inputs.arch) }}
+
+    - id: uname
+      name: uname
+      shell: bash
+      run: |
+        echo uname=`${SETARCH} uname -m` >> "$GITHUB_OUTPUT"
+        echo dpkg=`${SETARCH} uname -m | sed s/686/386/` >> "$GITHUB_OUTPUT"
+
+    - name: apt-get
+      shell: bash
+      env:
+        arch: ${{ inputs.arch && format(':{0}', steps.uname.outputs.dpkg) || '' }}
+      run: |
+        set -x
+        ${arch:+sudo dpkg --add-architecture ${arch#:}}
+        sudo apt-get update -qq || :
+        sudo apt-get install --no-install-recommends -qq -y -o=Dpkg::Use-Pty=0 \
+        ${arch:+cross}build-essential${arch/:/-} \
+        libssl-dev${arch} libyaml-dev${arch} libreadline6-dev${arch} \
+        zlib1g-dev${arch} libncurses5-dev${arch} libffi-dev${arch} \
+        autoconf ruby
+        sudo apt-get install -qq -y pkg-config${arch} || :
+
+    - uses: ruby/setup-ruby@a6e6f86333f0a2523ece813039b8b4be04560854 # v1.190.0
+      with:
+        ruby-version: '3.3'
+        bundler: none
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
new file mode 100644
index 0000000..f354db7
--- /dev/null
+++ b/.github/workflows/tests.yml
@@ -0,0 +1,96 @@
+name: MMTk
+on:
+  push:
+    paths-ignore:
+      - '**.md'
+  pull_request:
+    # Do not use paths-ignore for required status checks
+    # https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/collaborating-on-repositories-with-code-quality-features/troubleshooting-required-status-checks#handling-skipped-but-required-checks
+  merge_group:
+
+permissions:
+  contents: read
+
+jobs:
+  check:
+    strategy:
+      fail-fast: false
+      matrix:
+        gc:
+          - mmtk_plan: MarkSweep
+            mmtk_build: release
+            timeout: 120
+          - mmtk_plan: MarkSweep
+            mmtk_build: debug
+            timeout: 120
+        os: [macos-latest, ubuntu-latest]
+
+    env:
+      GITPULLOPTIONS: --no-tags origin ${{ github.ref }}
+      RUBY_DEBUG: ci
+
+    runs-on: ${{ matrix.os }}
+
+    if: >-
+      ${{!(false
+      || contains(github.event.head_commit.message, '[DOC]')
+      || contains(github.event.head_commit.message, 'Document')
+      || contains(github.event.pull_request.title, '[DOC]')
+      || contains(github.event.pull_request.title, 'Document')
+      || contains(github.event.pull_request.labels.*.name, 'Documentation')
+      || (github.event_name == 'push' && github.event.pull_request.user.login == 'dependabot[bot]')
+      )}}
+
+    steps:
+      - uses: actions/checkout@d632683dd7b4114ad314bca15554477dd762a938 # v4.2.0
+
+      - name: Install libraries (macOS)
+        uses: ./.github/actions/setup/macos
+        if: ${{ contains(matrix.os, 'macos') }}
+
+      - name: Install libraries (Ubuntu)
+        uses: ./.github/actions/setup/ubuntu
+        if: ${{ contains(matrix.os, 'ubuntu') }}
+
+      - uses: actions-rust-lang/setup-rust-toolchain@v1
+      - name: Set MMTk environment variables
+        run: |
+          if [[ ${{ matrix.gc.mmtk_build }} == debug ]]; then
+            echo 'RUST_LOG=' >> $GITHUB_ENV
+          fi
+          echo 'RUBY_TEST_TIMEOUT_SCALE=20' >> $GITHUB_ENV
+          echo 'SYNTAX_SUGGEST_TIMEOUT=60' >> $GITHUB_ENV
+          echo 'EXCLUDES=../../test/.excludes-mmtk' >> $GITHUB_ENV
+          echo 'MSPECOPT=-B../../spec/mmtk.mspec' >> $GITHUB_ENV
+          echo 'MMTK_PLAN=${{ matrix.gc.mmtk_plan }}' >> $GITHUB_ENV
+
+      - name: Install Bundler dependencies
+        run: bundle install
+
+      - name: build Ruby & MMTk shared GC
+        run: rake compile
+
+      - name: Verify MMTk bindgen
+        run: |
+          cd gc/mmtk
+          cargo install --force cbindgen
+          cbindgen --config cbindgen.toml --output ../mmtk.h
+          if read -n1 -d '' < <(git diff ../mmtk.h); then
+            git diff ../mmtk.h
+            exit 1
+          fi
+
+      - name: make check
+        run: >-
+          RUST_LOG= make -s check
+          ${TESTS:+TESTS="$TESTS"}
+        timeout-minutes: ${{ matrix.gc.timeout || 40 }}
+        working-directory: ./res/ruby
+        env:
+          RUBY_TESTOPTS: '-q --tty=no'
+          TEST_BUNDLED_GEMS_ALLOW_FAILURES: 'typeprof'
+          PRECHECK_BUNDLED_GEMS: 'no'
+          RUBY_GC_LIBRARY: mmtk
+
+
+