diff --git a/.travis.yml b/.travis.yml
index 3530a8c..5f7df5f 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -13,6 +13,14 @@ addons:
 language: php
 matrix:
   include:
+    - php: 7.2
+      env:
+        - MAGENTO_VERSION=2.2
+        - TEST_SUITE=unit
+    - php: 7.3
+      env:
+        - MAGENTO_VERSION=2.3-develop
+        - TEST_SUITE=unit
     - php: 7.2
       env:
         - MAGENTO_VERSION=2.2
diff --git a/.travis/before_script.sh b/.travis/before_script.sh
index 154ddc6..d8d55d4 100755
--- a/.travis/before_script.sh
+++ b/.travis/before_script.sh
@@ -25,8 +25,13 @@ cd magento2
 composer config minimum-stability dev
 composer config repositories.travis_to_test git https://github.com/$TRAVIS_REPO_SLUG.git
 #TODO make it work with tags as well:
+
 composer require ${COMPOSER_PACKAGE_NAME}:dev-${TRAVIS_BRANCH}\#{$TRAVIS_COMMIT}
 
+# Install dev dependencies of module
+php ../.travis/merge-dev.php vendor/$COMPOSER_PACKAGE_NAME/composer.json composer.json
+composer update
+
 # prepare for test suite
 case $TEST_SUITE in
     integration)
diff --git a/.travis/merge-dev.php b/.travis/merge-dev.php
new file mode 100644
index 0000000..8f411c3
--- /dev/null
+++ b/.travis/merge-dev.php
@@ -0,0 +1,23 @@
+<?php
+/*
+ * Merge autoload-dev and require-dev from one composer.json into another one
+ * 
+ * This is used to install the module within a Magento 2 installation, but with its dev dependencies
+ */
+declare(strict_types=1);
+
+$fromFile = $argv[1];
+$toFile = $argv[2];
+
+$fromJson = json_decode(file_get_contents($fromFile), true);
+$toJson = json_decode(file_get_contents($toFile), true);
+
+foreach ($fromJson['autoload-dev']['psr-4'] ?? [] as $key => $value) {
+    $pathPrefix = dirname($fromFile) . DIRECTORY_SEPARATOR;
+    $fromJson['autoload-dev']['psr-4'][$key] = $pathPrefix . $value;
+}
+
+$toJson['require-dev'] = array_replace_recursive($toJson['require-dev'] ?? [], $fromJson['require-dev']);
+$toJson['autoload-dev'] = array_merge_recursive($toJson['autoload-dev'] ?? [], $fromJson['autoload-dev']);
+
+file_put_contents($toFile, json_encode($toJson, JSON_PRETTY_PRINT));
\ No newline at end of file
diff --git a/composer.json b/composer.json
index 656f1ed..390bd6c 100755
--- a/composer.json
+++ b/composer.json
@@ -26,10 +26,15 @@
       "src/registration.php"
     ],
     "psr-4": {
-      "IntegerNet\\AsyncVarnish\\Test\\": "tests/",
       "IntegerNet\\AsyncVarnish\\": "src/"
     }
   },
+  "autoload-dev": {
+    "psr-4": {
+      "IntegerNet\\AsyncVarnish\\Test\\": "tests/",
+      "IntegerNet\\AsyncVarnish\\": "tests/src/"
+    }
+  },
   "repositories": [
     {
       "type": "composer",
@@ -37,6 +42,6 @@
     }
   ],
   "require-dev": {
-    "magento/magento-coding-standard": "@dev"
+    "react/http": "0.8.5"
   }
 }
diff --git a/src/Api/TagRepositoryInterface.php b/src/Api/TagRepositoryInterface.php
new file mode 100644
index 0000000..0e9048c
--- /dev/null
+++ b/src/Api/TagRepositoryInterface.php
@@ -0,0 +1,37 @@
+<?php
+declare(strict_types=1);
+
+namespace IntegerNet\AsyncVarnish\Api;
+
+interface TagRepositoryInterface
+{
+    /**
+     * Insert multiple Tags
+     *
+     * @param string[] $tags
+     * @return int
+     * @throws \Exception
+     */
+    public function insertMultiple(array $tags = []): int;
+
+    /**
+     * Delete multiple Tags by max entity_id
+     *
+     * @param int $maxId
+     * @return int
+     * @throws \Exception
+     */
+    public function deleteUpToId(int $maxId = 0): int;
+
+    /**
+     * @throws \Zend_Db_Statement_Exception
+     */
+    public function getAll(): array;
+
+    /**
+     * Return last ID (after getAll() call)
+     *
+     * @return int
+     */
+    public function getLastUsedId(): int;
+}
diff --git a/src/Model/PurgeAsyncCache.php b/src/Model/PurgeAsyncCache.php
index d190b1b..6f57769 100644
--- a/src/Model/PurgeAsyncCache.php
+++ b/src/Model/PurgeAsyncCache.php
@@ -3,8 +3,8 @@
 
 namespace IntegerNet\AsyncVarnish\Model;
 
-use Magento\CacheInvalidate\Model\PurgeCache as PurgeCache;
-use IntegerNet\AsyncVarnish\Model\TagRepository as TagRepository;
+use Magento\CacheInvalidate\Model\PurgeCache;
+use IntegerNet\AsyncVarnish\Model\TagRepository;
 use Magento\Framework\App\Config\ScopeConfigInterface;
 
 class PurgeAsyncCache
@@ -46,7 +46,7 @@ private function getMaxHeaderLengthFromConfig()
      * @throws \Zend_Db_Statement_Exception
      * @throws \Exception
      */
-    public function run():int
+    public function run(): int
     {
         $tags = $this->tagRepository->getAll();
         $maxHeaderLength = $this->getMaxHeaderLengthFromConfig();
diff --git a/src/Model/ResourceModel/Tag.php b/src/Model/ResourceModel/Tag.php
index f3120eb..1daab7b 100644
--- a/src/Model/ResourceModel/Tag.php
+++ b/src/Model/ResourceModel/Tag.php
@@ -22,11 +22,10 @@ public function getMaxTagId(int $limit):array
         $connection = $this->getConnection();
 
         $subSetSelect = $connection->select()->from(
-            self::TABLE_NAME,
+            $this->getTable(self::TABLE_NAME),
             ['entity_id','tag']
         )->order(
-            'entity_id',
-            'ASC'
+            'entity_id ASC'
         )->limit(
             $limit
         );
@@ -44,7 +43,7 @@ public function getUniqueTagsByMaxId(int $maxId):array
         $connection = $this->getConnection();
 
         $select = $connection->select()->from(
-            ['main_table' => self::TABLE_NAME],
+            ['main_table' => $this->getTable(self::TABLE_NAME)],
             ['tag']
         )->group(
             'tag'
diff --git a/src/Model/TagRepository.php b/src/Model/TagRepository.php
index b556291..c1229d6 100644
--- a/src/Model/TagRepository.php
+++ b/src/Model/TagRepository.php
@@ -3,11 +3,12 @@
 
 namespace IntegerNet\AsyncVarnish\Model;
 
+use IntegerNet\AsyncVarnish\Api\TagRepositoryInterface;
 use Magento\Framework\App\ResourceConnection;
 use IntegerNet\AsyncVarnish\Model\ResourceModel\Tag as TagResource;
 use Magento\Framework\App\Config\ScopeConfigInterface;
 
-class TagRepository
+class TagRepository implements TagRepositoryInterface
 {
     /**
      * DB Storage table name
@@ -19,6 +20,9 @@ class TagRepository
      */
     const FETCH_TAG_LIMIT_CONFIG_PATH = 'system/full_page_cache/async_varnish/varnish_fetch_tag_limit';
 
+    /**
+     * @var int|null
+     */
     private $lastUsedId;
 
     /**
@@ -52,9 +56,9 @@ public function __construct(
         $this->scopeConfig = $scopeConfig;
     }
 
-    private function getTagFetchLimit()
+    private function getTagFetchLimit(): int
     {
-        return $this->scopeConfig->getValue(self::FETCH_TAG_LIMIT_CONFIG_PATH);
+        return (int) $this->scopeConfig->getValue(self::FETCH_TAG_LIMIT_CONFIG_PATH);
     }
 
     /**
@@ -64,7 +68,7 @@ private function getTagFetchLimit()
      * @return int
      * @throws \Exception
      */
-    public function insertMultiple($tags = [])
+    public function insertMultiple($tags = []): int
     {
         if (empty($tags)) {
             return 0;
@@ -92,7 +96,7 @@ function ($tag) {
      * @return int
      * @throws \Exception
      */
-    public function deleteUpToId($maxId = 0)
+    public function deleteUpToId(int $maxId = 0): int
     {
         try {
             $tableName = $this->resource->getTableName(self::TABLE_NAME);
@@ -103,10 +107,9 @@ public function deleteUpToId($maxId = 0)
     }
 
     /**
-     * @return array
      * @throws \Zend_Db_Statement_Exception
      */
-    public function getAll()
+    public function getAll(): array
     {
 
         $tags = [];
@@ -120,24 +123,21 @@ public function getAll()
             return $tags;
         }
 
-        $maxId = $maxIdResult['max_id'];
+        $maxId = (int)$maxIdResult['max_id'];
 
-        $uniqueTagsResult = $tagResource->getUniqueTagsByMaxId((int)$maxId);
+        $uniqueTagsResult = $tagResource->getUniqueTagsByMaxId($maxId);
 
         if (!empty($uniqueTagsResult)) {
             $this->lastUsedId = $maxId;
 
             foreach ($uniqueTagsResult as $tag) {
-                $tags[] = ($tag['tag']);
+                $tags[] = $tag['tag'];
             }
         }
         return $tags;
     }
 
-    /**
-     * @return int
-     */
-    public function getLastUsedId()
+    public function getLastUsedId(): int
     {
         return $this->lastUsedId ?: 0;
     }
diff --git a/src/etc/di.xml b/src/etc/di.xml
index 6e6a05b..5673de7 100644
--- a/src/etc/di.xml
+++ b/src/etc/di.xml
@@ -12,4 +12,6 @@
             </argument>
         </arguments>
     </type>
+    <preference for="IntegerNet\AsyncVarnish\Api\TagRepositoryInterface"
+                type="IntegerNet\AsyncVarnish\Model\TagRepository" />
 </config>
\ No newline at end of file
diff --git a/tests/Integration/AbstractTagRepositoryTest.php b/tests/Integration/AbstractTagRepositoryTest.php
new file mode 100644
index 0000000..1a13dc9
--- /dev/null
+++ b/tests/Integration/AbstractTagRepositoryTest.php
@@ -0,0 +1,78 @@
+<?php
+declare(strict_types=1);
+
+namespace IntegerNet\AsyncVarnish\Test\Integration;
+
+use IntegerNet\AsyncVarnish\Api\TagRepositoryInterface;
+use PHPUnit\Framework\TestCase;
+
+abstract class AbstractTagRepositoryTest extends TestCase
+{
+    /**
+     * @var TagRepositoryInterface
+     */
+    protected $tagRepository;
+
+    protected function setUp()
+    {
+        $this->tagRepository = $this->getTestSubject();
+    }
+
+    abstract protected function getTestSubject(): TagRepositoryInterface;
+
+    public function testInsertAndRetrieve()
+    {
+        $affected = $this->tagRepository->insertMultiple(['x', 'y', 'z']);
+        $this->assertEquals(3, $affected, 'insertMultiple() should return number of inserted rows');
+        $this->assertEqualsCanonicalizing(['x', 'y', 'z'], $this->tagRepository->getAll());
+    }
+
+    public function testNoDuplicatesAreRetrieved()
+    {
+        $affected = $this->tagRepository->insertMultiple(['x', 'y', 'x']);
+        $this->assertEquals(3, $affected, 'insertMultiple() should return number of inserted rows');
+        $this->assertEqualsCanonicalizing(['x', 'y'], $this->tagRepository->getAll());
+    }
+
+    public function testNoDuplicatesAreRetrievedAfterSubsequentCalls()
+    {
+        $affected = $this->tagRepository->insertMultiple(['x', 'y']);
+        $this->assertEquals(2, $affected, 'insertMultiple() should return number of inserted rows');
+        $affected = $this->tagRepository->insertMultiple(['y', 'z']);
+        $this->assertEquals(2, $affected, 'insertMultiple() should return number of inserted rows');
+        $this->assertEqualsCanonicalizing(['x', 'y', 'z'], $this->tagRepository->getAll());
+    }
+
+    public function testLastUsedIdIncreases()
+    {
+        $this->tagRepository->insertMultiple(['x']);
+        $this->tagRepository->getAll();
+        $lastUsedId = $this->tagRepository->getLastUsedId();
+        $this->tagRepository->insertMultiple(['y']);
+        $this->tagRepository->getAll();
+        //TODO maybe throw exception if getAll has not been called before:
+        $this->assertEquals($lastUsedId + 1, $this->tagRepository->getLastUsedId());
+    }
+
+    public function testDeleteUpToId()
+    {
+        $this->tagRepository->insertMultiple(['x', 'y', 'z']);
+        $this->tagRepository->getAll();
+        $lastUsedId = $this->tagRepository->getLastUsedId();
+        $this->tagRepository->insertMultiple(['a', 'b', 'c']);
+        $affected = $this->tagRepository->deleteUpToId($lastUsedId);
+        $this->assertEquals(3, $affected, 'deleteUpToId() should return number of deleted rows');
+        $this->assertEqualsCanonicalizing(['a', 'b', 'c'], $this->tagRepository->getAll());
+    }
+
+    /**
+     * Backport from PHPUnit 8
+     *
+     * @param array $expected
+     * @param array $actual
+     */
+    public static function assertEqualsCanonicalizing(array $expected, array $actual, string $message = '')
+    {
+        self::assertEquals($expected, $actual, $message, 0.0, 10, true);
+    }
+}
diff --git a/tests/Integration/ModuleTest.php b/tests/Integration/ModuleTest.php
new file mode 100644
index 0000000..865824e
--- /dev/null
+++ b/tests/Integration/ModuleTest.php
@@ -0,0 +1,44 @@
+<?php
+declare(strict_types=1);
+
+namespace IntegerNet\AsyncVarnish\Test\Integration;
+
+use Magento\Framework\Component\ComponentRegistrar;
+use Magento\Framework\Module\ModuleList;
+use Magento\TestFramework\ObjectManager;
+use PHPUnit\Framework\TestCase;
+
+class ModuleTest extends TestCase
+{
+
+    /**
+     * @var ObjectManager
+     */
+    private $objectManager;
+    const MODULE_NAME = 'IntegerNet_AsyncVarnish';
+    /**
+     * @return ModuleList
+     */
+    private function getTestModuleList()
+    {
+        /** @var ModuleList $moduleList */
+        $moduleList = $this->objectManager->create(ModuleList::class);
+        return $moduleList;
+    }
+    protected function setUp()
+    {
+        $this->objectManager = ObjectManager::getInstance();
+    }
+    public function testTheModuleIsRegistered()
+    {
+        $registrar = new ComponentRegistrar();
+        $paths = $registrar->getPaths(ComponentRegistrar::MODULE);
+        $this->assertArrayHasKey(self::MODULE_NAME, $paths, 'Module should be registered');
+    }
+    public function testTheModuleIsKnownAndEnabled()
+    {
+        $moduleList = $this->getTestModuleList();
+        $this->assertTrue($moduleList->has(self::MODULE_NAME),  'Module should be enabled');
+    }
+
+}
\ No newline at end of file
diff --git a/tests/Integration/PurgeCacheTest.php b/tests/Integration/PurgeCacheTest.php
new file mode 100644
index 0000000..5caa888
--- /dev/null
+++ b/tests/Integration/PurgeCacheTest.php
@@ -0,0 +1,135 @@
+<?php
+declare(strict_types=1);
+
+namespace IntegerNet\AsyncVarnish\Test\Integration;
+
+use Magento\CacheInvalidate\Model\PurgeCache;
+use Magento\Framework\App\DeploymentConfig;
+use Magento\TestFramework\Helper\Bootstrap;
+use Magento\TestFramework\ObjectManager;
+use PHPUnit\Framework\TestCase;
+use Symfony\Component\Process\PhpExecutableFinder;
+use Symfony\Component\Process\Process;
+
+/**
+ * @magentoAppIsolation enabled
+ */
+class PurgeCacheTest extends TestCase
+{
+    /**
+     * Full path to varnish mock server
+     */
+    private const MOCK_SERVER_DIR  = __DIR__ . '/VarnishMock';
+    /**
+     * Request log, as written by VarnishMock/server.php
+     */
+    private const REQUEST_LOG_FILE = self::MOCK_SERVER_DIR . '/.requests.log';
+    /**
+     * Mock server port as used in VarnishMock/server.php
+     */
+    private const MOCK_SERVER_PORT = '8082';
+    /**
+     * @var Process
+     */
+    private $mockServerProcess;
+    /**
+     * @var PurgeCache
+     */
+    private $purgeCache;
+
+    protected function setUp()
+    {
+        $this->startMockServer();
+        $this->createRequestLog();
+
+        $this->configureVarnishHost();
+        $this->purgeCache = Bootstrap::getObjectManager()->get(PurgeCache::class);
+    }
+
+    private function configureVarnishHost()
+    {
+        /** @var ObjectManager $objectManager */
+        $objectManager = Bootstrap::getObjectManager();
+        $deploymentConfig = new DeploymentConfig(
+            $objectManager->get(DeploymentConfig\Reader::class),
+            ['http_cache_hosts' => [['host' => '127.0.0.1', 'port' => self::MOCK_SERVER_PORT]]]
+        );
+        $objectManager->addSharedInstance(
+            $deploymentConfig,
+            DeploymentConfig::class
+        );
+    }
+
+    protected function tearDown()
+    {
+        $this->stopMockServer();
+    }
+
+    public function testWebserver()
+    {
+        $this->assertEquals("OK\n", \file_get_contents('http://127.0.0.1:' . self::MOCK_SERVER_PORT . '/'));
+    }
+
+    public function testPurgeRequestIsSentToVarnish()
+    {
+        $tagsPattern = 'XXX|YYY|ZZZZ';
+        $result = $this->purgeCache->sendPurgeRequest($tagsPattern);
+        $this->assertTrue($result);
+        $this->assertEquals(
+            [
+                [
+                    'method'  => 'PURGE',
+                    'headers' => ['Host' => ['127.0.0.1'], 'X-Magento-Tags-Pattern' => [$tagsPattern]],
+                ],
+            ],
+            $this->getRequestsFromLog()
+        );
+    }
+
+    private function startMockServer(): void
+    {
+        $objectManager = Bootstrap::getObjectManager();
+        /** @var PhpExecutableFinder $phpExecutableFinder */
+        $phpExecutableFinder = $objectManager->get(PhpExecutableFinder::class);
+        $mockServerCmd = $phpExecutableFinder->find() . ' ' . self::MOCK_SERVER_DIR . '/server.php';
+        //the following needs Symfony Process >= 4.2.0
+//        $this->mockServerProcess = Process::fromShellCommandline($mockServerCmd);
+        //so we use the old way to instantiate Process from string:
+        $this->mockServerProcess = new Process($mockServerCmd);
+        $this->mockServerProcess->start();
+        //the following needs Symfony Process >= 4.2.0
+//        $this->mockServerProcess->waitUntil(
+//            function($output) {
+//                return $output === 'Started';
+//            }
+//        );
+        // so we wait a second or two instead:
+        sleep(2);
+    }
+
+    private function stopMockServer(): void
+    {
+        // issue: this only kills the parent shell script, not the PHP process (Symfony Process 4.1)
+//        $this->mockServerProcess->stop();
+        // so we implemented a kill switch in the server:
+        $ch = \curl_init('http://127.0.0.1:8082/?kill=1');
+        \curl_exec($ch);
+    }
+
+    private function createRequestLog(): void
+    {
+        \file_put_contents(self::REQUEST_LOG_FILE, '');
+        \chmod(self::REQUEST_LOG_FILE, 0666);
+    }
+
+    private function getRequestsFromLog(): array
+    {
+        $requests = \array_map(
+            function (string $line): array {
+                return \json_decode($line, true);
+            },
+            \file(self::REQUEST_LOG_FILE)
+        );
+        return $requests;
+    }
+}
diff --git a/tests/Integration/TagRepositoryTest.php b/tests/Integration/TagRepositoryTest.php
new file mode 100644
index 0000000..662baa0
--- /dev/null
+++ b/tests/Integration/TagRepositoryTest.php
@@ -0,0 +1,21 @@
+<?php
+declare(strict_types=1);
+
+namespace IntegerNet\AsyncVarnish\Test\Integration;
+
+use IntegerNet\AsyncVarnish\Api\TagRepositoryInterface;
+use IntegerNet\AsyncVarnish\Model\TagRepository;
+use Magento\TestFramework\Helper\Bootstrap;
+
+/**
+ * @magentoAppIsolation enabled
+ * @magentoDbIsolation enabled
+ */
+class TagRepositoryTest extends AbstractTagRepositoryTest
+{
+    protected function getTestSubject(): TagRepositoryInterface
+    {
+        $objectManager = Bootstrap::getObjectManager();
+        return $objectManager->get(TagRepository::class);
+    }
+}
diff --git a/tests/Integration/VarnishMock/.gitignore b/tests/Integration/VarnishMock/.gitignore
new file mode 100644
index 0000000..89267c3
--- /dev/null
+++ b/tests/Integration/VarnishMock/.gitignore
@@ -0,0 +1 @@
+/.requests.log
\ No newline at end of file
diff --git a/tests/Integration/VarnishMock/server.php b/tests/Integration/VarnishMock/server.php
new file mode 100644
index 0000000..17a1dc9
--- /dev/null
+++ b/tests/Integration/VarnishMock/server.php
@@ -0,0 +1,38 @@
+<?php
+declare(strict_types=1);
+$autoloadFiles = [__DIR__ . '/../../../vendor/autoload.php', __DIR__ . '/../../../../../autoload.php'];
+foreach ($autoloadFiles as $autoloadFile) {
+    if (stream_resolve_include_path($autoloadFile)) {
+        require $autoloadFile;
+        break;
+    }
+}
+$loop = \React\EventLoop\Factory::create();
+
+$server = new \React\Http\Server(function (\Psr\Http\Message\ServerRequestInterface $request) {
+    if ($request->getQueryParams()['kill'] ?? false) {
+        exit;
+    }
+    $requestJson = \json_encode(
+        [
+            'method'  => $request->getMethod(),
+            'headers' => $request->getHeaders()
+        ]
+    );
+    \file_put_contents(__DIR__ . '/.requests.log', $requestJson . "\n", FILE_APPEND);
+
+    return new \React\Http\Response(
+        200,
+        array(
+            'Content-Type' => 'text/plain'
+        ),
+        "OK\n"
+    );
+});
+
+$socket = new \React\Socket\Server(8082, $loop);
+$server->listen($socket);
+
+echo "Started";
+
+$loop->run();
diff --git a/tests/Unit/FakeTagRepositoryTest.php b/tests/Unit/FakeTagRepositoryTest.php
new file mode 100644
index 0000000..be3743a
--- /dev/null
+++ b/tests/Unit/FakeTagRepositoryTest.php
@@ -0,0 +1,17 @@
+<?php
+declare(strict_types=1);
+
+namespace IntegerNet\AsyncVarnish\Test\Unit;
+
+use IntegerNet\AsyncVarnish\Api\TagRepositoryInterface;
+use IntegerNet\AsyncVarnish\FakeTagRepository;
+use IntegerNet\AsyncVarnish\Test\Integration\AbstractTagRepositoryTest;
+
+class FakeTagRepositoryTest extends AbstractTagRepositoryTest
+{
+    protected function getTestSubject(): TagRepositoryInterface
+    {
+        return new FakeTagRepository();
+    }
+
+}
\ No newline at end of file
diff --git a/tests/Unit/phpunit.xml.dist b/tests/Unit/phpunit.xml.dist
new file mode 100644
index 0000000..427019c
--- /dev/null
+++ b/tests/Unit/phpunit.xml.dist
@@ -0,0 +1,40 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:noNamespaceSchemaLocation="http://schema.phpunit.de/6.2/phpunit.xsd"
+         colors="true"
+         beStrictAboutTestsThatDoNotTestAnything="false"
+         bootstrap="./framework/bootstrap.php"
+        >
+    <testsuite name="Local Unit Tests">
+        <directory suffix="Test.php">../../../vendor/integer-net/magento2-async-varnish/tests/Unit</directory>
+    </testsuite>
+    <php>
+        <ini name="date.timezone" value="America/Los_Angeles"/>
+        <ini name="xdebug.max_nesting_level" value="200"/>
+    </php>
+    <filter>
+        <whitelist addUncoveredFilesFromWhiteList="true">
+            <directory suffix=".php">../../src/app/code/*</directory>
+            <exclude>
+                <directory>../../src/app/code/*/*/Test</directory>
+            </exclude>
+        </whitelist>
+    </filter>
+    <listeners>
+        <listener class="Magento\Framework\TestFramework\Unit\Listener\ReplaceObjectManager"/>
+    </listeners>
+    <logging>
+        <!--coverage_html_placeholder
+            <log type="coverage-html" target="{{coverage_dir}}/test-reports/coverage" charset="UTF-8" yui="true" highlight="true"/>
+        coverage_html_placeholder-->
+        <!--coverage_cov_placeholder
+            <log type="coverage-php" target="{{coverage_dir}}/test-reports/coverage.cov"/>
+        coverage_cov_placeholder-->
+        <!--coverage_clover_placeholder
+            <log type="coverage-clover" target="{{coverage_dir}}/test-reports/phpunit.coverage.xml"/>
+        coverage_clover_placeholder-->
+        <!--coverage_crap4j_placeholder
+            <log type="coverage-crap4j" target="{{coverage_dir}}/test-reports/phpunit.crap4j.xml"/>
+        coverage_crap4j_placeholder-->
+    </logging>
+</phpunit>
diff --git a/tests/src/FakeTagRepository.php b/tests/src/FakeTagRepository.php
new file mode 100644
index 0000000..229283e
--- /dev/null
+++ b/tests/src/FakeTagRepository.php
@@ -0,0 +1,57 @@
+<?php
+declare(strict_types=1);
+
+namespace IntegerNet\AsyncVarnish;
+
+use IntegerNet\AsyncVarnish\Api\TagRepositoryInterface;
+
+class FakeTagRepository implements TagRepositoryInterface
+{
+    /**
+     * @var string[]
+     */
+    private $tags = [];
+
+    public function insertMultiple(array $tags = []): int
+    {
+        $this->tags = array_merge($this->tags, $tags);
+        return count($tags);
+    }
+
+    public function deleteUpToId(int $maxId = 0): int
+    {
+        $deleted = 0;
+        foreach ($this->tags as $key => $tag) {
+            if ($key <= $maxId) {
+                unset($this->tags[$key]);
+                ++$deleted;
+            }
+        }
+        return $deleted;
+    }
+
+    public function getAll(): array
+    {
+        return array_unique($this->tags);
+    }
+
+    public function getLastUsedId(): int
+    {
+        return array_key_last($this->tags);
+    }
+
+}
+
+/*
+ * PHP 7.2 Polyfill
+ */
+if (!\function_exists('array_key_last')) {
+    function array_key_last(array $array)
+    {
+        if (empty($array)) {
+            return null;
+        }
+
+        return key(array_slice($array, -1, 1, true));
+    }
+}
\ No newline at end of file

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