Add CI job running the tests against a real PostgreSQL service

.github/workflows/junit-tests.yml

@@ -24,3 +24,41 @@ jobs:
         cache: maven
     - name: Build with Maven
       run: mvn test
+
+  # The `build` job above runs the suite against in-memory H2, which never
+  # exercises the PostgreSQL driver this sample actually ships with. This job
+  # reruns the same tests against a real PostgreSQL server so that regressions
+  # in the org.postgresql:r2dbc-postgresql path are caught.
+  build-postgres:
+
+    runs-on: ubuntu-latest
+
+    services:
+      postgres:
+        image: postgres:16
+        env:
+          POSTGRES_USER: postgres
+          POSTGRES_PASSWORD: postgres
+          POSTGRES_DB: demo
+        ports:
+        - 5432:5432
+        options: >-
+          --health-cmd "pg_isready -U postgres -d demo"
+          --health-interval 10s
+          --health-timeout 5s
+          --health-retries 5
+
+    steps:
+    - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+    - name: Set up Java
+      uses: actions/setup-java@dd06d9cba3e5552c54d9f8ea23572deb30010f7c # v6.0.0
+      with:
+        java-version: 17
+        distribution: temurin
+        cache: maven
+    - name: Build with Maven
+      run: mvn test
+      env:
+        SPRING_R2DBC_URL: r2dbc:postgresql://localhost:5432/demo
+        SPRING_R2DBC_USERNAME: postgres
+        SPRING_R2DBC_PASSWORD: postgres