diff --git a/.gitignore b/.gitignore
index b19cdaf..e787af5 100644
--- a/.gitignore
+++ b/.gitignore
@@ -3,4 +3,5 @@ vendor
 nbproject/*
 .idea
 composer.lock
-build
\ No newline at end of file
+build
+.phpunit.result.cache
\ No newline at end of file
diff --git a/composer.json b/composer.json
index b6071ab..214673a 100644
--- a/composer.json
+++ b/composer.json
@@ -6,7 +6,7 @@
     "keywords": ["mailerlite", "sdk", "email", "marketing"],
     "type": "library",
     "require": {
-        "php" : "^7.1",
+        "php" : "^7.1 || ^8.0",
         "php-http/client-common": "^2.0",
         "php-http/discovery": "^1.7",
         "nyholm/psr7": "^1.0",
diff --git a/phpunit.xml b/phpunit.xml
index e968daf..0735d25 100644
--- a/phpunit.xml
+++ b/phpunit.xml
@@ -1,16 +1,15 @@
-<phpunit bootstrap="tests/bootstrap.php"
-         colors="true"
-         stopOnFailure="false">
+<?xml version="1.0"?>
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" bootstrap="tests/bootstrap.php" colors="true" stopOnFailure="false" xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/9.3/phpunit.xsd">
+  <coverage/>
   <testsuites>
     <testsuite name="client">
       <directory>tests</directory>
     </testsuite>
   </testsuites>
   <logging>
-    <log type="tap" target="build/report.tap"/>
-    <log type="junit" target="build/report.junit.xml"/>
+    <junit outputFile="build/report.junit.xml"/>
     <!-- <log type="coverage-html" target="build/coverage" charset="UTF-8" yui="true" highlight="true"/>
     <log type="coverage-text" target="build/coverage.txt"/>
     <log type="coverage-clover" target="build/logs/clover.xml"/> -->
   </logging>
-</phpunit>
\ No newline at end of file
+</phpunit>
diff --git a/phpunit.xml.bak b/phpunit.xml.bak
new file mode 100644
index 0000000..e968daf
--- /dev/null
+++ b/phpunit.xml.bak
@@ -0,0 +1,16 @@
+<phpunit bootstrap="tests/bootstrap.php"
+         colors="true"
+         stopOnFailure="false">
+  <testsuites>
+    <testsuite name="client">
+      <directory>tests</directory>
+    </testsuite>
+  </testsuites>
+  <logging>
+    <log type="tap" target="build/report.tap"/>
+    <log type="junit" target="build/report.junit.xml"/>
+    <!-- <log type="coverage-html" target="build/coverage" charset="UTF-8" yui="true" highlight="true"/>
+    <log type="coverage-text" target="build/coverage.txt"/>
+    <log type="coverage-clover" target="build/logs/clover.xml"/> -->
+  </logging>
+</phpunit>
\ No newline at end of file
diff --git a/tests/BatchTest.php b/tests/BatchTest.php
index ea03703..93caf46 100644
--- a/tests/BatchTest.php
+++ b/tests/BatchTest.php
@@ -46,14 +46,14 @@ public function send_batch()
             ->setMethod(BatchRequest::METHOD_POST)
             ->setPath('/api/v2/subscribers')
             ->setBody([
-                'email' => 'one@batch.com',
+                'email' => BATCH_TEST_EMAIL1,
             ]);
 
         $batchTwo = (new BatchRequest())
             ->setMethod(BatchRequest::METHOD_POST)
             ->setPath('/api/v2/subscribers')
             ->setBody([
-                'email' => 'two@batch.com',
+                'email' => BATCH_TEST_EMAIL2,
             ]);
 
         $requests[] = $batchOne;
diff --git a/tests/CampaignsTest.php b/tests/CampaignsTest.php
index 980ebb4..e481000 100644
--- a/tests/CampaignsTest.php
+++ b/tests/CampaignsTest.php
@@ -24,7 +24,7 @@ public function create_campaign()
         $campaignData = [
             'subject' => 'Regular Campaign Subject',
             'type' => 'regular',
-            'groups' => [2984475, 3237221] // TODO: improve this with creating new groups
+            'groups' => [CAMPAIGNS_TEST_GROUP1, CAMPAIGNS_TEST_GROUP2] // TODO: improve this with creating new groups
         ];
 
         $campaign = $this->campaignsApi->create($campaignData);
diff --git a/tests/SegmentsTest.php b/tests/SegmentsTest.php
index f8d9d44..5d88215 100644
--- a/tests/SegmentsTest.php
+++ b/tests/SegmentsTest.php
@@ -25,6 +25,6 @@ public function get_segments()
     {
         $segments = $this->segmentsApi->get();
 
-        $this->assertContains('Demo segment', (array) $segments->first()->data[0]);
+        $this->assertContains(SEGMENTS_TEST_NAME1, (array) $segments->first()->data[0]);
     }
 }
diff --git a/tests/SubscribersTest.php b/tests/SubscribersTest.php
index 4fc0ce6..3b4ec34 100644
--- a/tests/SubscribersTest.php
+++ b/tests/SubscribersTest.php
@@ -67,7 +67,7 @@ public function update_subscriber()
     /** @test **/
     public function search_for_a_subscriber()
     {
-        $subscribers = $this->subscribersApi->search('demo@mailerlite.com');
+        $subscribers = $this->subscribersApi->search(SUBSCRIBERS_TEST_EMAIL1);
 
         $this->assertTrue(count($subscribers) > 0);
     }
diff --git a/tests/bootstrap.php b/tests/bootstrap.php
index 09f15fd..6334726 100644
--- a/tests/bootstrap.php
+++ b/tests/bootstrap.php
@@ -1,4 +1,21 @@
 <?php
+
 require_once __DIR__ . '/../vendor/autoload.php';
 
-define('API_KEY', 'fc7b8c5b32067bcd47cafb5f475d2fe9'); // demo account
\ No newline at end of file
+// demo account
+define('API_KEY', 'fc7b8c5b32067bcd47cafb5f475d2fe9');
+define('BATCH_TEST_EMAIL1', 'one@batch.com');
+define('BATCH_TEST_EMAIL2', 'two@batch.com');
+define('SUBSCRIBERS_TEST_EMAIL1', 'demo@mailerlite.com');
+define('CAMPAIGNS_TEST_GROUP1', 2984475);
+define('CAMPAIGNS_TEST_GROUP2', 3237221);
+define('SEGMENTS_TEST_NAME1', 'Demo segment');
+
+// other account (other devs) (adapt below as required)
+// define('API_KEY', 'XXX');
+// define('BATCH_TEST_EMAIL1', 'email.one@example.com');
+// define('BATCH_TEST_EMAIL2', 'email.two@example.com');
+// define('SUBSCRIBERS_TEST_EMAIL1', 'subscriber.one@example.com');
+// define('CAMPAIGNS_TEST_GROUP1', 000000000);
+// define('CAMPAIGNS_TEST_GROUP2', 000000000);
+// define('SEGMENTS_TEST_NAME1', 'SDK Test');
\ No newline at end of file