diff --git a/.github/workflows/php.yml b/.github/workflows/php.yml
index 5059597..89602b7 100644
--- a/.github/workflows/php.yml
+++ b/.github/workflows/php.yml
@@ -10,11 +10,24 @@ jobs:
   build:
     strategy:
       matrix:
-        php-versions: ["7.2", "7.3", "7.4", "8.0"]
+        # The library supports PHP 5.5+, but PHPUnit 8.5 needs 7.2 or later
+        php-versions: ["7.2", "7.3", "7.4", "8.0", "8.1", "8.2", "8.3", "8.4"]
     runs-on: ubuntu-latest
 
+    # The integration tests use Redis on 127.0.0.1:6379
+    services:
+      redis:
+        image: redis
+        ports:
+          - 6379:6379
+        options: >-
+          --health-cmd "redis-cli ping"
+          --health-interval 5s
+          --health-timeout 5s
+          --health-retries 10
+
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
 
       - name: Setup PHP, with composer and extensions
         uses: shivammathur/setup-php@v2 #https://github.com/shivammathur/setup-php
@@ -23,20 +36,24 @@ jobs:
           extensions: mbstring, simplexml, dom, curl
           coverage: pcov
 
-      - name: Validate composer.json and composer.lock
+      - name: Validate composer.json
         run: composer validate --strict
 
       - name: Cache Composer packages
         id: composer-cache
-        uses: actions/cache@v2
+        uses: actions/cache@v4
         with:
           path: vendor
-          key: ${{ runner.os }}-php-${{ hashFiles('**/composer.lock') }}
+          key: ${{ runner.os }}-php-${{ matrix.php-versions }}-${{ hashFiles('composer.json') }}
           restore-keys: |
-            ${{ runner.os }}-php-
-            
+            ${{ runner.os }}-php-${{ matrix.php-versions }}-
+
+      # There's no committed composer.lock, so resolve for each PHP version
       - name: Install dependencies
         run: composer update --prefer-dist --no-progress
 
-      - name: Run test suite
+      - name: Run unit tests
         run: composer run-script test
+
+      - name: Run integration tests
+        run: vendor/bin/phpunit --testsuite integration