setup-ocaml@v2, sans test

.github/workflows/blank.yml

@@ -1,5 +1,3 @@
-# This is a basic workflow to help you get started with Actions
-
 name: CI
 
 # Controls when the action will run. 
@@ -7,25 +5,29 @@ on:
   # Allows you to run this workflow manually from the Actions tab
   workflow_dispatch:
 
-# A workflow run is made up of one or more jobs that can run sequentially or in parallel
 jobs:
-  # This workflow contains a single job called "build"
   build:
-    # The type of runner that the job will run on
-    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        os:
+          - macos-latest
+          - ubuntu-latest
+          - windows-latest
+        ocaml-compiler:
+          - 4.12.x
+
+    runs-on: ${{ matrix.os }}
 
-    # Steps represent a sequence of tasks that will be executed as part of the job
     steps:
-      # Checks-out your repository under $GITHUB_WORKSPACE, so your job can access it
-      - uses: actions/checkout@v2
+      - name: Checkout code
+        uses: actions/checkout@v2
 
-      # Runs a single command using the runners shell
-      - name: Run a one-line script
-        run: echo Hello, world!
-        
-      - name: Setu up OCaml
-        uses: ocaml/setup-ocaml@v1.1.11
+      - name: Use OCaml ${{ matrix.ocaml-compiler }}
+        uses: ocaml/setup-ocaml@v2
+        with:
+          ocaml-compiler: ${{ matrix.ocaml-compiler }}
 
-      # Runs a set of commands using the runners shell
-      - name: Run a multi-line script
-        run: dune build
+      - run: opam install . --deps-only
+
+      - run: opam exec -- dune build