diff --git a/core/modules/image/tests/src/Functional/ImageStylesPathAndUrlTest.php b/core/modules/image/tests/src/Functional/ImageStylesPathAndUrlTest.php
index 678f3718..1cd7ce2e 100644
--- a/core/modules/image/tests/src/Functional/ImageStylesPathAndUrlTest.php
+++ b/core/modules/image/tests/src/Functional/ImageStylesPathAndUrlTest.php
@@ -465,7 +465,7 @@ public function testImageStyleUrlAndPath(string $scheme, bool $clean_url, bool $
 
     // Make sure that language prefix is never added to the image style URL.
     if ($langcode) {
-      $this->assertNotContains("/$langcode/", $generate_url);
+      $this->assertStringNotContainsString("/$langcode/", $generate_url);
     }
 
     // Ensure that the tests still pass when the file is generated by accessing
@@ -484,7 +484,7 @@ public function testImageStyleUrlAndPath(string $scheme, bool $clean_url, bool $
 
     // When using non-clean URLS, the system path contains the script name.
     if (!$clean_url) {
-      $this->assertContains('index.php/', $generate_url);
+      $this->assertStringContainsString('index.php/', $generate_url);
     }
 
     // Add some extra chars to the token.
@@ -525,7 +525,7 @@ public function testImageStyleUrlAndPath(string $scheme, bool $clean_url, bool $
 
     if ($scheme == 'private') {
       $this->assertSame('Sun, 19 Nov 1978 05:00:00 GMT', $this->drupalGetHeader('Expires'));
-      $this->assertContains('no-cache', $this->drupalGetHeader('Cache-Control'));
+      $this->assertStringContainsString('no-cache', $this->drupalGetHeader('Cache-Control'));
       $this->assertSame('image_module_test', $this->drupalGetHeader('X-Image-Owned-By'));
 
       // Make sure that a second request to the already existing derivative
@@ -560,16 +560,16 @@ public function testImageStyleUrlAndPath(string $scheme, bool $clean_url, bool $
       $this->assertResponse(403, 'Confirmed that access is denied for the private image style.');
       // Verify that images are not appended to the response.
       // Currently this test only uses PNG images.
-      $this->assertContains('.png', $generate_url, 'Confirming that private image styles are not appended require PNG file.');
+      $this->assertStringContainsString('.png', $generate_url, 'Confirming that private image styles are not appended require PNG file.');
       // Check for PNG-Signature
       // (cf. http://www.libpng.org/pub/png/book/chapter08.html#png.ch08.div.2)
       // in the response body.
       $raw = $this->getSession()->getPage()->getContent();
-      $this->assertNotContains(chr(137) . chr(80) . chr(78) . chr(71) . chr(13) . chr(10) . chr(26) . chr(10), $raw);
+      $this->assertStringNotContainsString(chr(137) . chr(80) . chr(78) . chr(71) . chr(13) . chr(10) . chr(26) . chr(10), $raw);
     }
     else {
       $this->assertSame('Sun, 19 Nov 1978 05:00:00 GMT', $this->drupalGetHeader('Expires'), 'Expires header was sent.');
-      $this->assertNotContains('no-cache', $this->drupalGetHeader('Cache-Control'));
+      $this->assertStringNotContainsString('no-cache', $this->drupalGetHeader('Cache-Control'));
 
       if ($clean_url) {
         // Add some extra chars to the token.
@@ -603,7 +603,7 @@ public function testImageStyleUrlAndPath(string $scheme, bool $clean_url, bool $
     $generated_uri = $pipeline->getDerivativeImageUri();
     $this->assertFileNotExists($generated_uri, 'Generated file does not exist.');
     $generate_url = $pipeline->getDerivativeImageUrl()->toString();
-    $this->assertNotContains(IMAGE_DERIVATIVE_TOKEN . '=', $generate_url, 'The security token does not appear in the image style URL.');
+    $this->assertStringNotContainsString(IMAGE_DERIVATIVE_TOKEN . '=', $generate_url, 'The security token does not appear in the image style URL.');
     $this->drupalGet($generate_url);
     $this->assertResponse(200, 'Image was accessible at the URL with a missing token.');
 
diff --git a/core/modules/image/tests/src/Kernel/DerivativeImageProcessTest.php b/core/modules/image/tests/src/Kernel/DerivativeImageProcessTest.php
index 24f7c5ba..5f9627be 100644
--- a/core/modules/image/tests/src/Kernel/DerivativeImageProcessTest.php
+++ b/core/modules/image/tests/src/Kernel/DerivativeImageProcessTest.php
@@ -36,7 +36,7 @@ class DerivativeImageProcessTest extends KernelTestBase {
   /**
    * {@inheritdoc}
    */
-  protected function setUp() {
+  protected function setUp(): void {
     parent::setUp();
     $this->installConfig(['system', 'image']);
     $this->imageProcessor = \Drupal::service('image.processor');
diff --git a/core/modules/image/tests/src/Kernel/ImageStyleLegacyTest.php b/core/modules/image/tests/src/Kernel/ImageStyleLegacyTest.php
index 3f6e7700..7f4dbccf 100644
--- a/core/modules/image/tests/src/Kernel/ImageStyleLegacyTest.php
+++ b/core/modules/image/tests/src/Kernel/ImageStyleLegacyTest.php
@@ -33,7 +33,7 @@ class ImageStyleLegacyTest extends KernelTestBase {
   /**
    * {@inheritdoc}
    */
-  protected function setUp() {
+  protected function setUp(): void {
     parent::setUp();
 
     $this->imageStyle = ImageStyle::create([
@@ -58,7 +58,7 @@ public function testBuildUri() {
    * @expectedDeprecation The Drupal\image\Entity\ImageStyle::buildUrl method is deprecated since version 9.x.x and will be removed in y.y.y.
    */
   public function testBuildUrl() {
-    $this->assertContains('files/styles/test/public/test.png?itok=', $this->imageStyle->buildUrl('public://test.png'));
+    $this->assertStringContainsString('files/styles/test/public/test.png?itok=', $this->imageStyle->buildUrl('public://test.png'));
   }
 
   /**
@@ -66,7 +66,7 @@ public function testBuildUrl() {
    * @expectedDeprecation The Drupal\image\Entity\ImageStyle::createDerivative method is deprecated since version 9.x.x and will be removed in y.y.y.
    */
   public function testCreateDerivative() {
-    $this->assertInternalType('bool', $this->imageStyle->createDerivative('public://test.png', 'public://test_derivative.png'));
+    $this->assertIsBool($this->imageStyle->createDerivative('public://test.png', 'public://test_derivative.png'));
   }
 
   /**