Add CI based testing, with related fix.

Fix missing version for the dune dependency.

.github/workflows/workflow.yml

@@ -0,0 +1,78 @@
+name: Build, test, and lint
+
+on:
+  - push
+  - pull_request
+
+permissions: read-all
+
+jobs:
+  build-and-test:
+
+    services:
+      mariadb:
+        image: mariadb:latest
+        ports: ["3306:3306"]
+        env:
+          MARIADB_USER: testuser
+          MARIADB_PASSWORD: testpw
+          MARIADB_DATABASE: testdb
+          MARIADB_RANDOM_ROOT_PASSWORD: 1
+
+    strategy:
+      fail-fast: false
+      matrix:
+        os:
+          - ubuntu-latest
+          # ubuntu-20.04 has the same MariaDB client library options as latest
+          # macos-latest does not work since we're using a service container
+        ocaml-compiler:
+          - 5
+          - 4.07
+
+    runs-on: ${{ matrix.os }}
+
+    steps:
+      - name: Check out source code
+        uses: actions/checkout@v4
+
+      - name: Set up OCaml
+        uses: ocaml/setup-ocaml@v3
+        with:
+          ocaml-compiler: ${{ matrix.ocaml-compiler }}
+
+      - name: Restore cached dependencies
+        uses: actions/cache@v3
+        with:
+          key: ${{ runner.os }}-ocaml-${{ matrix.ocaml-compiler }}-deps-${{ hashFiles('*.opam') }}
+          path: ~/.opam
+
+      - name: Install dependencies
+        run: opam install . --deps-only -t
+
+      - name: Build
+        run: opam exec -- dune build
+
+      - name: Run tests
+        run: opam exec -- dune runtest
+        env:
+          OCAML_MARIADB_HOST: 127.0.0.1
+          OCAML_MARIADB_PORT: 3306
+          OCAML_MARIADB_USER: testuser
+          OCAML_MARIADB_PASS: testpw
+          OCAML_MARIADB_DB: testdb
+          OCAML_MARIADB_QUERY: "SELECT 'hello ' || ?"
+
+  lint-opam:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out source code
+        uses: actions/checkout@v4
+
+      - name: Set up OCaml
+        uses: ocaml/setup-ocaml@v3
+        with:
+          ocaml-compiler: 5
+
+      - name: Lint OPAM package descriptions
+        uses: ocaml/setup-ocaml/lint-opam@v3

mariadb.opam

@@ -22,7 +22,7 @@ depends: [
   "ctypes" {>= "0.7.0"}
   "conf-mariadb"
   "conf-gcc"
-  "dune"
+  "dune" {>= "3.15.0"}
   "dune-configurator"
   "async" {with-test}
   "lwt" {with-test}