diff --git a/.github/workflows/macos.yml b/.github/workflows/macos.yml
deleted file mode 100644
index 70cedfd8..00000000
--- a/.github/workflows/macos.yml
+++ /dev/null
@@ -1,22 +0,0 @@
-name: macos
-
-on: [push, pull_request]
-
-jobs:
-  build:
-    runs-on: macos-latest
-    strategy:
-      matrix:
-        ruby: [ '2.6.x', '2.5.x', '2.4.x' ]
-    steps:
-    - uses: actions/checkout@master
-    - name: Set up Ruby
-      uses: actions/setup-ruby@v1
-      with:
-        ruby-version: ${{ matrix.ruby }}
-    - name: Set up Bundler
-      run: gem install bundler --no-document
-    - name: Install dependencies
-      run: bundle install
-    - name: Run test
-      run: rake
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index b65270a2..e1dee1d7 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -3,25 +3,22 @@ name: test
 on: [push, pull_request]
 
 jobs:
-  test:
-    runs-on: ubuntu-latest
-
+  build:
+    name: build (${{ matrix.ruby }} / ${{ matrix.os }})
     strategy:
       matrix:
-        ruby: [head, 2.6.0, 2.5.3, 2.4.5, 2.3.8]
-
+        ruby: [ 2.7, 2.6, 2.5, head ]
+        os: [ ubuntu-latest, macos-latest ]
+    runs-on: ${{ matrix.os }}
     steps:
-    - name: Checkout code
-      uses: actions/checkout@v2
-
+    - uses: actions/checkout@master
     - name: Set up Ruby
       uses: ruby/setup-ruby@v1
       with:
         ruby-version: ${{ matrix.ruby }}
-
     - name: Install dependencies
-      run: bundle install
-
-    - name: Run tests
-      run: rake
-      continue-on-error: ${{ matrix.ruby == '2.3.8' || matrix.ruby == '2.4.5' }}
+      run: |
+        gem install bundler --no-document
+        bundle install
+    - name: Run test
+      run: rake test
diff --git a/.github/workflows/ubuntu-rvm.yml b/.github/workflows/ubuntu-rvm.yml
deleted file mode 100644
index 17538d06..00000000
--- a/.github/workflows/ubuntu-rvm.yml
+++ /dev/null
@@ -1,33 +0,0 @@
-name: ubuntu-rvm
-
-on: [push, pull_request]
-
-jobs:
-  build:
-    runs-on: ubuntu-latest
-    strategy:
-      matrix:
-        ruby: [ 'ruby-head' ]
-      fail-fast: false
-    steps:
-    - uses: actions/checkout@master
-    - name: Set up RVM
-      run: |
-        curl -sSL https://get.rvm.io | bash
-    - name: Set up Ruby
-      run: |
-        source $HOME/.rvm/scripts/rvm
-        rvm install ${{ matrix.ruby }} --binary
-        rvm --default use ${{ matrix.ruby }}
-    - name: Set up Bundler
-      run: |
-        source $HOME/.rvm/scripts/rvm
-        gem install bundler --no-document
-    - name: Install dependencies
-      run: |
-        source $HOME/.rvm/scripts/rvm
-        bundle install
-    - name: Run test
-      run: |
-        source $HOME/.rvm/scripts/rvm
-        rake
diff --git a/.github/workflows/ubuntu.yml b/.github/workflows/ubuntu.yml
deleted file mode 100644
index 8d461076..00000000
--- a/.github/workflows/ubuntu.yml
+++ /dev/null
@@ -1,22 +0,0 @@
-name: ubuntu
-
-on: [push, pull_request]
-
-jobs:
-  build:
-    runs-on: ubuntu-latest
-    strategy:
-      matrix:
-        ruby: [ '2.6.x', '2.5.x', '2.4.x' ]
-    steps:
-    - uses: actions/checkout@master
-    - name: Set up Ruby
-      uses: actions/setup-ruby@v1
-      with:
-        ruby-version: ${{ matrix.ruby }}
-    - name: Set up Bundler
-      run: gem install bundler --no-document
-    - name: Install dependencies
-      run: bundle install
-    - name: Run test
-      run: rake