diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..a6e38be
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,78 @@
+name: CI
+
+on:
+  push:
+
+  pull_request:
+    branches:
+      - '*'
+
+permissions:
+  contents: read
+
+jobs:
+  testsuite:
+    name: PHP ${{ matrix.php-version }}
+    runs-on: ubuntu-24.04
+    strategy:
+      fail-fast: false
+      matrix:
+        # composer.json declares php >=8.1 and cakephp/cakephp ^5.0.
+        # CakePHP 5.0-5.2 allow PHP 8.1; 5.3+ requires PHP 8.2, so on 8.1
+        # composer resolves 5.2.x and on 8.2+ the latest 5.x. Test the whole
+        # declared range: 8.1 (min) -> 8.5 (newest).
+        php-version: ['8.1', '8.2', '8.3', '8.4', '8.5']
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: ${{ matrix.php-version }}
+          extensions: mbstring, intl, apcu, sqlite3, pdo_sqlite
+          ini-values: apc.enable_cli=1
+          coverage: none
+
+      - name: Get composer cache directory
+        id: composer-cache
+        run: echo "dir=$(composer config cache-files-dir)" >> "$GITHUB_OUTPUT"
+
+      - name: Cache composer dependencies
+        uses: actions/cache@v4
+        with:
+          path: ${{ steps.composer-cache.outputs.dir }}
+          key: ${{ runner.os }}-composer-${{ matrix.php-version }}-${{ hashFiles('composer.json') }}
+          restore-keys: ${{ runner.os }}-composer-${{ matrix.php-version }}-
+
+      - name: Install dependencies
+        # composer.lock is gitignored, so resolve dependencies on each run.
+        run: composer update --prefer-dist --no-interaction --no-progress
+
+      - name: Run PHPUnit
+        run: vendor/bin/phpunit
+
+  cs-stan:
+    name: Coding Standard & Static Analysis
+    runs-on: ubuntu-24.04
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: '8.2'
+          extensions: mbstring, intl, apcu
+          coverage: none
+
+      - name: Install dependencies
+        run: composer update --prefer-dist --no-interaction --no-progress
+
+      - name: Run PHP CodeSniffer
+        run: composer cs-check
+
+      # NOTE: phpstan/psalm are pinned to 1.10.14 / 5.10.0 in .phive/phars.xml;
+      # those versions do not run on PHP 8.2+ (fatal in better-reflection) and
+      # report pre-existing findings. Modernize the pins in a separate change
+      # before wiring them back into CI as a blocking step.
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
new file mode 100644
index 0000000..bd68de9
--- /dev/null
+++ b/phpunit.xml.dist
@@ -0,0 +1,34 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+  ~ Copyright 2013 - 2023, Cake Development Corporation (https://www.cakedc.com)
+  ~
+  ~ Licensed under The MIT License
+  ~ Redistributions of files must retain the above copyright notice.
+  ~
+  ~ @copyright Copyright 2013 - 2023, Cake Development Corporation (https://www.cakedc.com)
+  ~ @license MIT License (http://www.opensource.org/licenses/mit-license.php)
+  -->
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         colors="true"
+         processIsolation="false"
+         stopOnFailure="false"
+         bootstrap="tests/bootstrap.php"
+         cacheDirectory=".phpunit.cache"
+         xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/10.1/phpunit.xsd">
+    <php>
+        <ini name="memory_limit" value="-1"/>
+        <ini name="apc.enable_cli" value="1"/>
+    </php>
+
+    <testsuites>
+        <testsuite name="DbTest Test Suite">
+            <directory>tests/TestCase/</directory>
+        </testsuite>
+    </testsuites>
+
+    <source>
+        <include>
+            <directory suffix=".php">src/</directory>
+        </include>
+    </source>
+</phpunit>
diff --git a/src/TestSuite/Fixture/Extension/PHPUnitBeforeTestMethodCalledSubscriber.php b/src/TestSuite/Fixture/Extension/PHPUnitBeforeTestMethodCalledSubscriber.php
deleted file mode 100644
index 9761215..0000000
--- a/src/TestSuite/Fixture/Extension/PHPUnitBeforeTestMethodCalledSubscriber.php
+++ /dev/null
@@ -1,35 +0,0 @@
-<?php
-declare(strict_types=1);
-
-/**
- * Copyright 2013 - 2023, Cake Development Corporation (https://www.cakedc.com)
- *
- * Licensed under The MIT License
- * Redistributions of files must retain the above copyright notice.
- *
- * @copyright Copyright 2013 - 2023, Cake Development Corporation (https://www.cakedc.com)
- * @license MIT License (http://www.opensource.org/licenses/mit-license.php)
- */
-namespace CakeDC\DbTest\TestSuite\Fixture\Extension;
-
-use Cake\Database\Connection;
-use Cake\Datasource\ConnectionManager;
-use PHPUnit\Event\Test\BeforeTestMethodCalled;
-use PHPUnit\Event\Test\BeforeTestMethodCalledSubscriber;
-
-/**
- * PHPUnitBeforeTestMethodCalledSubscriber
- */
-class PHPUnitBeforeTestMethodCalledSubscriber implements BeforeTestMethodCalledSubscriber
-{
-    /**
-     * @param \PHPUnit\Event\Test\BeforeTestMethodCalled $event Event
-     * @return void
-     */
-    public function notify(BeforeTestMethodCalled $event): void
-    {
-        $connection = ConnectionManager::get('test');
-        assert($connection instanceof Connection);
-        $connection->begin();
-    }
-}
diff --git a/src/TestSuite/Fixture/Extension/PHPUnitExtension.php b/src/TestSuite/Fixture/Extension/PHPUnitExtension.php
index 978bd0d..81203ca 100644
--- a/src/TestSuite/Fixture/Extension/PHPUnitExtension.php
+++ b/src/TestSuite/Fixture/Extension/PHPUnitExtension.php
@@ -37,7 +37,7 @@ public function bootstrap(Configuration $configuration, Facade $facade, Paramete
 
         $facade->registerSubscribers(
             new PHPUnitStartedSubscriber($fixtureManager),
-            new PHPUnitBeforeTestMethodCalledSubscriber(),
+            new PHPUnitPreparationStartedSubscriber(),
             new PHPUnitAfterTestMethodFinishedSubscriber()
         );
     }
diff --git a/src/TestSuite/Fixture/Extension/PHPUnitPreparationStartedSubscriber.php b/src/TestSuite/Fixture/Extension/PHPUnitPreparationStartedSubscriber.php
new file mode 100644
index 0000000..fc4a38f
--- /dev/null
+++ b/src/TestSuite/Fixture/Extension/PHPUnitPreparationStartedSubscriber.php
@@ -0,0 +1,45 @@
+<?php
+declare(strict_types=1);
+
+/**
+ * Copyright 2013 - 2023, Cake Development Corporation (https://www.cakedc.com)
+ *
+ * Licensed under The MIT License
+ * Redistributions of files must retain the above copyright notice.
+ *
+ * @copyright Copyright 2013 - 2023, Cake Development Corporation (https://www.cakedc.com)
+ * @license MIT License (http://www.opensource.org/licenses/mit-license.php)
+ */
+namespace CakeDC\DbTest\TestSuite\Fixture\Extension;
+
+use Cake\Database\Connection;
+use Cake\Datasource\ConnectionManager;
+use PHPUnit\Event\Test\PreparationStarted;
+use PHPUnit\Event\Test\PreparationStartedSubscriber;
+
+/**
+ * Opens the per-test transaction before setUp() runs.
+ *
+ * PHPUnit emits PreparationStarted before the before-test hooks, so opening the
+ * transaction here keeps everything written in setUp() (fixtures, factories, save())
+ * inside the per-test transaction. The previous BeforeTestMethodCalled event is
+ * emitted after setUp(), which committed that data and leaked it into the following
+ * tests of the same class.
+ */
+class PHPUnitPreparationStartedSubscriber implements PreparationStartedSubscriber
+{
+    /**
+     * @param \PHPUnit\Event\Test\PreparationStarted $event Event
+     * @return void
+     */
+    public function notify(PreparationStarted $event): void
+    {
+        $connection = ConnectionManager::get('test');
+        assert($connection instanceof Connection);
+        // a previous test may have left its transaction open (e.g. unmet requirements)
+        if ($connection->inTransaction()) {
+            $connection->rollback(true);
+        }
+        $connection->begin();
+    }
+}
diff --git a/tests/TestCase/TestSuite/Fixture/Extension/PHPUnitPreparationStartedSubscriberTest.php b/tests/TestCase/TestSuite/Fixture/Extension/PHPUnitPreparationStartedSubscriberTest.php
new file mode 100644
index 0000000..082c9a5
--- /dev/null
+++ b/tests/TestCase/TestSuite/Fixture/Extension/PHPUnitPreparationStartedSubscriberTest.php
@@ -0,0 +1,167 @@
+<?php
+declare(strict_types=1);
+
+/**
+ * Copyright 2013 - 2023, Cake Development Corporation (https://www.cakedc.com)
+ *
+ * Licensed under The MIT License
+ * Redistributions of files must retain the above copyright notice.
+ *
+ * @copyright Copyright 2013 - 2023, Cake Development Corporation (https://www.cakedc.com)
+ * @license MIT License (http://www.opensource.org/licenses/mit-license.php)
+ */
+namespace CakeDC\DbTest\Test\TestCase\TestSuite\Fixture\Extension;
+
+use Cake\Database\Connection;
+use Cake\Datasource\ConnectionManager;
+use CakeDC\DbTest\TestSuite\Fixture\Extension\PHPUnitPreparationStartedSubscriber;
+use PHPUnit\Event\Code\Test as EventTest;
+use PHPUnit\Event\Telemetry\Duration;
+use PHPUnit\Event\Telemetry\GarbageCollectorStatus;
+use PHPUnit\Event\Telemetry\HRTime;
+use PHPUnit\Event\Telemetry\Info;
+use PHPUnit\Event\Telemetry\MemoryUsage;
+use PHPUnit\Event\Telemetry\Snapshot;
+use PHPUnit\Event\Test\PreparationStarted;
+use PHPUnit\Event\Test\PreparationStartedSubscriber;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * PHPUnitPreparationStartedSubscriberTest
+ */
+class PHPUnitPreparationStartedSubscriberTest extends TestCase
+{
+    /**
+     * @var \Cake\Database\Connection
+     */
+    protected Connection $connection;
+
+    /**
+     * @return void
+     */
+    protected function setUp(): void
+    {
+        parent::setUp();
+
+        $this->connection = new class extends Connection {
+            /**
+             * @var array<string>
+             */
+            public array $calls = [];
+
+            /**
+             * @var bool
+             */
+            public bool $inTransaction = false;
+
+            /**
+             * Skip the parent constructor, the test never touches the driver.
+             */
+            public function __construct()
+            {
+            }
+
+            /**
+             * @return bool
+             */
+            public function inTransaction(): bool
+            {
+                return $this->inTransaction;
+            }
+
+            /**
+             * @return void
+             */
+            public function begin(): void
+            {
+                $this->calls[] = 'begin';
+                $this->inTransaction = true;
+            }
+
+            /**
+             * @param bool|null $toBeginning Whether the transaction should be rolled back to the beginning.
+             * @return bool
+             */
+            public function rollback(?bool $toBeginning = null): bool
+            {
+                $this->calls[] = 'rollback';
+                $this->inTransaction = false;
+
+                return true;
+            }
+        };
+
+        ConnectionManager::drop('test');
+        ConnectionManager::setConfig('test', $this->connection);
+    }
+
+    /**
+     * The subscriber opens the per-test transaction on the PreparationStarted event.
+     *
+     * @return void
+     */
+    public function testOpensTransactionOnPreparationStarted(): void
+    {
+        $subscriber = new PHPUnitPreparationStartedSubscriber();
+        $this->assertInstanceOf(PreparationStartedSubscriber::class, $subscriber);
+
+        $subscriber->notify($this->preparationStartedEvent());
+
+        $this->assertSame(['begin'], $this->connection->calls);
+    }
+
+    /**
+     * A transaction left open by a previous test is rolled back before beginning.
+     *
+     * @return void
+     */
+    public function testRollsBackAbandonedTransactionBeforeBeginning(): void
+    {
+        $this->connection->inTransaction = true;
+
+        (new PHPUnitPreparationStartedSubscriber())->notify($this->preparationStartedEvent());
+
+        $this->assertSame(['rollback', 'begin'], $this->connection->calls);
+    }
+
+    /**
+     * Builds a PreparationStarted event; the subscriber ignores the payload.
+     *
+     * @return \PHPUnit\Event\Test\PreparationStarted
+     */
+    protected function preparationStartedEvent(): PreparationStarted
+    {
+        $snapshot = new Snapshot(
+            HRTime::fromSecondsAndNanoseconds(0, 0),
+            MemoryUsage::fromBytes(0),
+            MemoryUsage::fromBytes(0),
+            new GarbageCollectorStatus(0, 0, 0, 0, null, null, null, null, null, null, null, null),
+        );
+        $telemetry = new Info(
+            $snapshot,
+            Duration::fromSecondsAndNanoseconds(0, 0),
+            MemoryUsage::fromBytes(0),
+            Duration::fromSecondsAndNanoseconds(0, 0),
+            MemoryUsage::fromBytes(0),
+        );
+        $test = new class ('PreparationStarted') extends EventTest {
+            /**
+             * @return string
+             */
+            public function id(): string
+            {
+                return 'CakeDC\DbTest\Test\TestCase\PreparationStarted::test';
+            }
+
+            /**
+             * @return string
+             */
+            public function name(): string
+            {
+                return 'test';
+            }
+        };
+
+        return new PreparationStarted($telemetry, $test);
+    }
+}