diff --git a/.gitignore b/.gitignore
index 088f5c9..fcf8e69 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,3 +2,4 @@ composer.lock
 vendor/
 coverage/
 .DS_Store
+.phpunit.result.cache
diff --git a/composer.json b/composer.json
index 17f867a..1bdf4d7 100644
--- a/composer.json
+++ b/composer.json
@@ -14,7 +14,7 @@
     "php": ">=5.5"
   },
   "require-dev": {
-    "phpunit/phpunit": "^4.8.13",
+    "phpunit/phpunit": "^8.5",
     "predis/predis": "1.1.*"
   },
   "autoload": {
diff --git a/tests/integration/CacheTest.php b/tests/integration/CacheTest.php
index 65e0350..89b023b 100644
--- a/tests/integration/CacheTest.php
+++ b/tests/integration/CacheTest.php
@@ -1,5 +1,5 @@
 <?php
-class CacheTest extends PHPUnit_Framework_TestCase {
+class CacheTest extends \PHPUnit\Framework\TestCase {
 
   public function testCreateFromConfig() {
     p3k\Cache::redis('tcp://127.0.0.1:6379');
diff --git a/tests/unit/DateTest.php b/tests/unit/DateTest.php
index f76bc93..acfffdc 100644
--- a/tests/unit/DateTest.php
+++ b/tests/unit/DateTest.php
@@ -1,5 +1,5 @@
 <?php
-class DateTest extends PHPUnit_Framework_TestCase {
+class DateTest extends \PHPUnit\Framework\TestCase {
 
   public function testFormatLocalPositiveOffset() {
     $local = p3k\date\format_local('c', '2017-05-01T13:30:00+0000', 7200);
diff --git a/tests/unit/URLTest.php b/tests/unit/URLTest.php
index 3fc0d4a..f040136 100644
--- a/tests/unit/URLTest.php
+++ b/tests/unit/URLTest.php
@@ -1,5 +1,5 @@
 <?php
-class URLTest extends PHPUnit_Framework_TestCase {
+class URLTest extends \PHPUnit\Framework\TestCase {
 
   public function testDisplayURL() {
     $url = p3k\url\display_url('http://example.com');
diff --git a/tests/unit/UtilsTest.php b/tests/unit/UtilsTest.php
index d6ff1ce..bb1004d 100644
--- a/tests/unit/UtilsTest.php
+++ b/tests/unit/UtilsTest.php
@@ -1,5 +1,5 @@
 <?php
-class UtilsTest extends PHPUnit_Framework_TestCase {
+class UtilsTest extends \PHPUnit\Framework\TestCase {
 
   public function testRandomString() {
     $str1 = p3k\random_string(20);