diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 816830b..6fc01e9 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -10,7 +10,7 @@ jobs:
   tests:
     strategy:
       matrix:
-        php-versions: ['7.3', '7.4']
+        php-versions: ['7.3', '7.4', '8.0', '8.1']
 
     runs-on: ubuntu-latest
 
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..3eb76cc
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,3 @@
+/.phpunit.cache
+/composer.lock
+/vendor
diff --git a/composer.json b/composer.json
index 55f2c2b..ef0f3a1 100644
--- a/composer.json
+++ b/composer.json
@@ -14,7 +14,7 @@
         "php": ">=5.3.0"
     },
     "require-dev": {
-        "phpunit/phpunit": "~4"
+        "phpunit/phpunit": "^9.5.21"
     },
     "autoload": {
         "psr-0": {
diff --git a/phpunit.xml b/phpunit.xml
new file mode 100644
index 0000000..fd5e558
--- /dev/null
+++ b/phpunit.xml
@@ -0,0 +1,26 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/9.5/phpunit.xsd"
+         bootstrap="vendor/autoload.php"
+         cacheResultFile=".phpunit.cache/test-results"
+         executionOrder="depends,defects"
+         beStrictAboutCoversAnnotation="true"
+         beStrictAboutOutputDuringTests="true"
+         beStrictAboutTodoAnnotatedTests="true"
+         convertDeprecationsToExceptions="true"
+         failOnRisky="true"
+         failOnWarning="true"
+         verbose="true">
+    <testsuites>
+        <testsuite name="default">
+            <directory>tests</directory>
+        </testsuite>
+    </testsuites>
+
+    <coverage cacheDirectory=".phpunit.cache/code-coverage"
+              processUncoveredFiles="true">
+        <include>
+            <directory suffix=".php">src</directory>
+        </include>
+    </coverage>
+</phpunit>
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
deleted file mode 100644
index c4c78cc..0000000
--- a/phpunit.xml.dist
+++ /dev/null
@@ -1,18 +0,0 @@
-<phpunit bootstrap="vendor/autoload.php">
-	<testsuite name="Tests">
-		<directory>./tests</directory>
-	</testsuite>
-
-	<filter>
-		<whitelist>
-			<directory suffix=".php">./src</directory>
-		</whitelist>
-	</filter>
-
-	<logging>
-		<log type="coverage-html" target="./log/report" charset="UTF-8" yui="true" highlight="true" lowUpperBound="50" highLowerBound="80" />
-		<log type="coverage-text" target="./log/coverage.txt"/>
-		<log type="coverage-clover" target="./log/coverage.xml"/>
-		<log type="testdox-html" target="./log/testdox.html" />
-	</logging>
-</phpunit>
\ No newline at end of file
diff --git a/src/vierbergenlars/LibJs/JSArray.php b/src/vierbergenlars/LibJs/JSArray.php
index dfd0668..43d48c7 100644
--- a/src/vierbergenlars/LibJs/JSArray.php
+++ b/src/vierbergenlars/LibJs/JSArray.php
@@ -194,7 +194,7 @@ public function rewind()
 
     public function valid()
     {
-        return each($this->array)!== false;
+        return key($this->array) !== null;
     }
 
     public function valueOf()
diff --git a/tests/JSArrayTest.php b/tests/JSArrayTest.php
new file mode 100644
index 0000000..598a00a
--- /dev/null
+++ b/tests/JSArrayTest.php
@@ -0,0 +1,25 @@
+<?php
+
+namespace vierbergenlars\SemVer\Tests;
+
+use PHPUnit\Framework\TestCase;
+use vierbergenlars\LibJs\JSArray;
+use vierbergenlars\LibJs\JString;
+
+/**
+ * @copyright ResearchGate GmbH
+ */
+class JSArrayTest extends TestCase
+{
+
+    public function testIterableJSArray()
+    {
+        $jsArray = new JSArray(array('1.0.0', '2.0.0'));
+        $versions = array();
+        foreach ($jsArray as $version) {
+            $versions[] = $version;
+        }
+
+        $this->assertEquals(array(new JString('1.0.0'), new JString('2.0.0')), $versions);
+    }
+}
diff --git a/tests/RegressionTest.php b/tests/RegressionTest.php
index 1daa441..b561d3c 100644
--- a/tests/RegressionTest.php
+++ b/tests/RegressionTest.php
@@ -2,9 +2,10 @@
 
 namespace vierbergenlars\SemVer\Tests;
 
+use PHPUnit\Framework\TestCase;
 use vierbergenlars\SemVer;
 
-class RegressionTest extends \PHPUnit_Framework_TestCase
+class RegressionTest extends TestCase
 {
     public function testBug23()
     {
diff --git a/tests/SemVerTest.php b/tests/SemVerTest.php
index f507112..dc27e7f 100644
--- a/tests/SemVerTest.php
+++ b/tests/SemVerTest.php
@@ -2,9 +2,10 @@
 
 namespace vierbergenlars\SemVer\Tests\Internal;
 
+use PHPUnit\Framework\TestCase;
 use vierbergenlars\SemVer\Internal as SemVer;
 
-class SemVerTest extends \PHPUnit_Framework_TestCase
+class SemVerTest extends TestCase
 {
     public function testComparison()
     {
diff --git a/tests/VersionTest.php b/tests/VersionTest.php
index ad44ea9..2b8ab80 100644
--- a/tests/VersionTest.php
+++ b/tests/VersionTest.php
@@ -2,9 +2,10 @@
 
 namespace vierbergenlars\SemVer\Tests;
 
+use PHPUnit\Framework\TestCase;
 use vierbergenlars\SemVer;
 
-class VersionTest extends \PHPUnit_Framework_TestCase
+class VersionTest extends TestCase
 {
     public function testKeepSimpleversion()
     {
@@ -238,19 +239,19 @@ public function testNotSatisfiedBy()
 
     /**
      * @dataProvider invalidSemanticVersionProvider
-     * @expectedException \vierbergenlars\SemVer\SemVerException
      */
     public function testInvalidExpressionString($version)
     {
+        $this->expectException(SemVer\SemVerException::class);
         new SemVer\expression($version);
     }
 
     /**
      * @dataProvider invalidSemanticVersionProvider
-     * @expectedException \vierbergenlars\SemVer\SemVerException
      */
     public function testInvalidVersionString($version)
     {
+        $this->expectException(SemVer\SemVerException::class);
         new SemVer\version($version);
     }