diff --git a/composer.json b/composer.json
index 51fb838..56e3ada 100644
--- a/composer.json
+++ b/composer.json
@@ -20,14 +20,15 @@
         }
     ],
     "require": {
-        "silverstripe/framework": "^4",
+        "php": "^7.3 || ^8.0",
+        "silverstripe/framework": "^4.10",
         "silverstripe/assets": "^1",
         "silverstripe/versioned": "^1",
         "guzzlehttp/guzzle": "~6.3.0"
     },
     "require-dev": {
         "squizlabs/php_codesniffer": "^3",
-        "sminnee/phpunit": "^5.7"
+        "phpunit/phpunit": "^9.5"
     },
     "autoload": {
         "psr-4": {
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index 8700f65..251c15c 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">
diff --git a/tests/FileTextExtractableTest.php b/tests/FileTextExtractableTest.php
index bb8a262..f840f5e 100644
--- a/tests/FileTextExtractableTest.php
+++ b/tests/FileTextExtractableTest.php
@@ -18,7 +18,7 @@ class FileTextExtractableTest extends SapphireTest
         ],
     ];
 
-    protected function setUp()
+    protected function setUp(): void
     {
         parent::setUp();
 
@@ -33,7 +33,7 @@ class FileTextExtractableTest extends SapphireTest
         );
     }
 
-    protected function tearDown()
+    protected function tearDown(): void
     {
         if (file_exists(dirname(__FILE__) . '/fixtures/test1-copy.html')) {
             unlink(dirname(__FILE__) . '/fixtures/test1-copy.html');
@@ -53,8 +53,8 @@ class FileTextExtractableTest extends SapphireTest
 
         $content = $file->extractFileAsText();
         $this->assertNotNull($content);
-        $this->assertContains('Test Headline', $content);
-        $this->assertContains('Test Text', $content);
+        $this->assertStringContainsString('Test Headline', $content);
+        $this->assertStringContainsString('Test Text', $content);
         $this->assertEquals($content, $file->FileContentCache);
     }
 }
diff --git a/tests/HTMLTextExtractorTest.php b/tests/HTMLTextExtractorTest.php
index 98c37bf..2d725f2 100644
--- a/tests/HTMLTextExtractorTest.php
+++ b/tests/HTMLTextExtractorTest.php
@@ -11,7 +11,7 @@ class HTMLTextExtractorTest extends SapphireTest
 {
     protected $usesDatabase = true;
 
-    protected function setUp()
+    protected function setUp(): void
     {
         parent::setUp();
 
@@ -28,9 +28,9 @@ class HTMLTextExtractorTest extends SapphireTest
 
         $content = $extractor->getContent($file);
 
-        $this->assertContains('Test Headline', $content);
-        $this->assertNotContains('Test Comment', $content, 'Strips HTML comments');
-        $this->assertNotContains('Test Style', $content, 'Strips non-content style tags');
-        $this->assertNotContains('Test Script', $content, 'Strips non-content script tags');
+        $this->assertStringContainsString('Test Headline', $content);
+        $this->assertStringNotContainsString('Test Comment', $content, 'Strips HTML comments');
+        $this->assertStringNotContainsString('Test Style', $content, 'Strips non-content style tags');
+        $this->assertStringNotContainsString('Test Script', $content, 'Strips non-content script tags');
     }
 }
diff --git a/tests/PDFTextExtractorTest.php b/tests/PDFTextExtractorTest.php
index 9e3fc02..dfa263a 100644
--- a/tests/PDFTextExtractorTest.php
+++ b/tests/PDFTextExtractorTest.php
@@ -24,6 +24,6 @@ class PDFTextExtractorTest extends SapphireTest
         $file->write();
 
         $content = $extractor->getContent($file);
-        $this->assertContains('This is a test file with a link', $content);
+        $this->assertStringContainsString('This is a test file with a link', $content);
     }
 }
diff --git a/tests/TikaServerTextExtractorTest.php b/tests/TikaServerTextExtractorTest.php
index 2239499..b47dfb0 100644
--- a/tests/TikaServerTextExtractorTest.php
+++ b/tests/TikaServerTextExtractorTest.php
@@ -2,7 +2,7 @@
 
 namespace SilverStripe\TextExtraction\Tests;
 
-use PHPUnit_Framework_MockObject_MockObject;
+use PHPUnit\Framework\MockObject\MockObject;
 use SilverStripe\Assets\File;
 use SilverStripe\Dev\SapphireTest;
 use SilverStripe\TextExtraction\Extractor\TikaServerTextExtractor;
@@ -28,7 +28,7 @@ class TikaServerTextExtractorTest extends SapphireTest
         $file->write();
 
         $content = $extractor->getContent($file);
-        $this->assertContains('This is a test file with a link', $content);
+        $this->assertStringContainsString('This is a test file with a link', $content);
 
         // Check mime validation
         $this->assertTrue($extractor->supportsMime('application/pdf'));
@@ -43,7 +43,7 @@ class TikaServerTextExtractorTest extends SapphireTest
      */
     public function testIsAvailable($version, $expected)
     {
-        /** @var PHPUnit_Framework_MockObject_MockObject|TikaServerTextExtractor $extractor */
+        /** @var MockObject|TikaServerTextExtractor $extractor */
         $extractor = $this->getMockBuilder(TikaServerTextExtractor::class)
             ->setMethods(['getClient', 'getServerEndpoint'])
             ->getMock();
diff --git a/tests/TikaTextExtractorTest.php b/tests/TikaTextExtractorTest.php
index e2674d2..2f35099 100644
--- a/tests/TikaTextExtractorTest.php
+++ b/tests/TikaTextExtractorTest.php
@@ -28,7 +28,7 @@ class TikaTextExtractorTest extends SapphireTest
         $file->write();
 
         $content = $extractor->getContent($file);
-        $this->assertContains('This is a test file with a link', $content);
+        $this->assertStringContainsString('This is a test file with a link', $content);
 
         // Check mime validation
         $this->assertTrue($extractor->supportsMime('application/pdf'));