diff --git a/composer.json b/composer.json
index 33a72d3..73f91f4 100644
--- a/composer.json
+++ b/composer.json
@@ -19,11 +19,12 @@
         "issues": "http://github.com/silverstripe/silverstripe-tagfield/issues"
     },
     "require": {
-        "silverstripe/framework": "^4.3",
+        "php": "^7.3 || ^8.0",
+        "silverstripe/framework": "^4.10",
         "silverstripe/versioned": "^1.3"
     },
     "require-dev": {
-        "sminnee/phpunit": "^5.7",
+        "phpunit/phpunit": "^9.5",
         "squizlabs/php_codesniffer": "^3.0"
     },
     "autoload": {
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index e190cd3..8a5bffa 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -1,7 +1,9 @@
 <phpunit bootstrap="vendor/silverstripe/framework/tests/bootstrap.php" colors="true">
-    <testsuite name="Default">
-        <directory>tests/</directory>
-    </testsuite>
+    <testsuites>
+        <testsuite name="Default">
+            <directory>tests/</directory>
+        </testsuite>
+    </testsuites>
     <filter>
         <whitelist addUncoveredFilesFromWhitelist="true">
             <directory suffix=".php">src/</directory>
diff --git a/tests/StringTagFieldTest.php b/tests/StringTagFieldTest.php
index 71dfa5c..74bb388 100755
--- a/tests/StringTagFieldTest.php
+++ b/tests/StringTagFieldTest.php
@@ -2,7 +2,6 @@
 
 namespace SilverStripe\TagField\Tests;
 
-use PHPUnit_Framework_TestCase;
 use SilverStripe\Control\HTTPRequest;
 use SilverStripe\Dev\SapphireTest;
 use SilverStripe\Forms\FieldList;
@@ -10,9 +9,6 @@ use SilverStripe\Forms\Form;
 use SilverStripe\TagField\StringTagField;
 use SilverStripe\TagField\Tests\Stub\StringTagFieldTestBlogPost;
 
-/**
- * @mixin PHPUnit_Framework_TestCase
- */
 class StringTagFieldTest extends SapphireTest
 {
     /**
@@ -133,7 +129,7 @@ class StringTagFieldTest extends SapphireTest
         $schema = $field->getSchemaDataDefaults();
         $this->assertTrue($schema['lazyLoad']);
         $this->assertTrue($schema['creatable']);
-        $this->assertContains('suggest', $schema['optionUrl']);
+        $this->assertStringContainsString('suggest', $schema['optionUrl']);
     }
 
     public function testSchemaIsAddedToAttributes()
diff --git a/tests/TagFieldTest.php b/tests/TagFieldTest.php
index 85a911c..4e24ea6 100755
--- a/tests/TagFieldTest.php
+++ b/tests/TagFieldTest.php
@@ -2,7 +2,6 @@
 
 namespace SilverStripe\TagField\Tests;
 
-use PHPUnit_Framework_TestCase;
 use SilverStripe\Control\HTTPRequest;
 use SilverStripe\Dev\SapphireTest;
 use SilverStripe\Forms\FieldList;
@@ -15,9 +14,6 @@ use SilverStripe\TagField\Tests\Stub\TagFieldTestBlogPost;
 use SilverStripe\TagField\Tests\Stub\TagFieldTestBlogTag;
 use SilverStripe\TagField\Tests\Stub\TagFieldTestController;
 
-/**
- * @mixin PHPUnit_Framework_TestCase
- */
 class TagFieldTest extends SapphireTest
 {
     /**
@@ -436,7 +432,7 @@ class TagFieldTest extends SapphireTest
         $schema = $field->getSchemaDataDefaults();
         $this->assertTrue($schema['lazyLoad']);
         $this->assertTrue($schema['creatable']);
-        $this->assertContains('suggest', $schema['optionUrl']);
+        $this->assertStringContainsString('suggest', $schema['optionUrl']);
     }
 
     public function testSchemaIsAddedToAttributes()