diff --git a/tests/src/FunctionalJavascript/FormatterTest.php b/tests/src/FunctionalJavascript/FormatterTest.php
index 4e8274c..0be6ece 100644
--- a/tests/src/FunctionalJavascript/FormatterTest.php
+++ b/tests/src/FunctionalJavascript/FormatterTest.php
@@ -220,7 +220,7 @@ class FormatterTest extends TestBase {
     $assert_session->elementExists('xpath', '//head/style[contains(string(), "color: yellow;")]');
     $element = $page->find('xpath', '//div[@class="grantne"]');
     $this->assertNotEmpty($element);
-    $this->assertContains('Testing Block', $element->getHtml());
+    $this->assertStringContainsString('Testing Block', $element->getHtml());
   }
 
   /**
@@ -250,9 +250,9 @@ class FormatterTest extends TestBase {
 
     // Verify default configuration in UI.
     $summary_markup = $this->getSummaryCell()->getHtml();
-    $this->assertContains('Location: HEAD', $summary_markup);
-    $this->assertContains('Selector Prefix: None', $summary_markup);
-    $this->assertNotContains('Fixed Prefix Value', $summary_markup);
+    $this->assertStringContainsString('Location: HEAD', $summary_markup);
+    $this->assertStringContainsString('Selector Prefix: None', $summary_markup);
+    $this->assertStringNotContainsString('Fixed Prefix Value', $summary_markup);
 
     // Verify default configuration in storage.
     $display_component = \Drupal::service('entity_display.repository')
@@ -284,9 +284,9 @@ class FormatterTest extends TestBase {
 
     // Verify summary.
     $summary_markup = $this->getSummaryCell()->getHtml();
-    $this->assertContains('Location: BODY', $summary_markup);
-    $this->assertContains('Selector Prefix: Fixed Value', $summary_markup);
-    $this->assertContains('Fixed Prefix Value: venango', $summary_markup);
+    $this->assertStringContainsString('Location: BODY', $summary_markup);
+    $this->assertStringContainsString('Selector Prefix: Fixed Value', $summary_markup);
+    $this->assertStringContainsString('Fixed Prefix Value: venango', $summary_markup);
 
     $page->pressButton('Save');
     $assert_session->pageTextContains('Your settings have been saved.');
diff --git a/tests/src/FunctionalJavascript/TestBase.php b/tests/src/FunctionalJavascript/TestBase.php
index fa594ff..eea7292 100644
--- a/tests/src/FunctionalJavascript/TestBase.php
+++ b/tests/src/FunctionalJavascript/TestBase.php
@@ -33,7 +33,7 @@ abstract class TestBase extends WebDriverTestBase {
   /**
    * {@inheritdoc}
    */
-  public static $modules = [
+  protected static $modules = [
     'field_css',
     'node',
   ];
@@ -41,7 +41,7 @@ abstract class TestBase extends WebDriverTestBase {
   /**
    * {@inheritdoc}
    */
-  public function setUp() {
+  public function setUp(): void {
     parent::setUp();
 
     $this->createContentType(['type' => 'page']);
diff --git a/tests/src/FunctionalJavascript/WidgetTest.php b/tests/src/FunctionalJavascript/WidgetTest.php
index fdb9dca..e678b06 100644
--- a/tests/src/FunctionalJavascript/WidgetTest.php
+++ b/tests/src/FunctionalJavascript/WidgetTest.php
@@ -121,8 +121,8 @@ class WidgetTest extends TestBase {
 
     // Verify default settings in summary.
     $summary_markup = $this->getSummaryCell()->getHtml();
-    $this->assertContains('Load toolbar: Yes', $summary_markup);
-    $this->assertContains('Toolbar buttons: undo, redo, enlarge, shrink', $summary_markup);
+    $this->assertStringContainsString('Load toolbar: Yes', $summary_markup);
+    $this->assertStringContainsString('Toolbar buttons: undo, redo, enlarge, shrink', $summary_markup);
 
     $page->pressButton('Save');
     $assert_session->pageTextContains('Your settings have been saved.');
@@ -150,8 +150,8 @@ class WidgetTest extends TestBase {
 
     // Verify updated settings in summary.
     $summary_markup = $this->getSummaryCell()->getHtml();
-    $this->assertContains('Load toolbar: Yes', $summary_markup);
-    $this->assertContains('Toolbar buttons: enlarge, shrink', $summary_markup);
+    $this->assertStringContainsString('Load toolbar: Yes', $summary_markup);
+    $this->assertStringContainsString('Toolbar buttons: enlarge, shrink', $summary_markup);
 
     $page->pressButton('Save');
     $assert_session->pageTextContains('Your settings have been saved.');
@@ -180,8 +180,8 @@ class WidgetTest extends TestBase {
 
     // Verify updated settings in summary.
     $summary_markup = $this->getSummaryCell()->getHtml();
-    $this->assertContains('Load toolbar: No', $summary_markup);
-    $this->assertNotContains('Toolbar buttons:', $summary_markup);
+    $this->assertStringContainsString('Load toolbar: No', $summary_markup);
+    $this->assertStringNotContainsString('Toolbar buttons:', $summary_markup);
 
     $page->pressButton('Save');
     $assert_session->pageTextContains('Your settings have been saved.');