diff --git a/core/tests/Drupal/FunctionalJavascriptTests/Core/Form/JavascriptStatesTest.php b/core/tests/Drupal/FunctionalJavascriptTests/Core/Form/JavascriptStatesTest.php
index 448cb9d..beee43b 100644
--- a/core/tests/Drupal/FunctionalJavascriptTests/Core/Form/JavascriptStatesTest.php
+++ b/core/tests/Drupal/FunctionalJavascriptTests/Core/Form/JavascriptStatesTest.php
@@ -21,20 +21,20 @@ class JavascriptStatesTest extends JavascriptTestBase {
    */
   public function testJavascriptStates() {
     $this->drupalGet('form-test/javascript-states-form');
-    $driver = $this->getSession()->getDriver();
+    $page = $this->getSession()->getPage();
 
     $this->assertElementNotVisible('#edit-name');
 
     // This should make the name element visible.
-    $this->click('#edit-anonymous');
+    $page->uncheckField('I prefer to remain anonymous');
     $this->assertElementVisible('#edit-name');
 
     // This should make the name element invisible.
-    $this->click('#edit-anonymous');
+    $page->checkField('I prefer to remain anonymous');
     $this->assertElementNotVisible('#edit-name');
 
     // This should make the name element visible.
-    $this->click('#edit-anonymous');
+    $page->uncheckField('I prefer to remain anonymous');
     $this->assertElementVisible('#edit-name');
 
     // Ensure all the details elements are invisible.
@@ -71,12 +71,12 @@ public function testJavascriptStates() {
     $this->assertElementVisible('#edit-average');
 
     $this->assertElementNotVisible('#edit-comment--description');
-    $driver->selectOption($this->cssSelect('#edit-how-many-years'), '5');
+    $page->selectFieldOption('How many years have you completed?', '5');
     $this->assertElementVisible('#edit-comment--description');
     $this->assertElementNotVisible('#edit-country-writein');
-    $driver->selectOption($this->cssSelect('#edit-school-country'), 'Other');
+    $page->selectFieldOption('In what country is your college or university located?', 'Other');
     $this->assertElementVisible('#edit-country-writein');
-    $driver->selectOption($this->cssSelect('#edit-school-country'), 'UK');
+    $page->selectFieldOption('In what country is your college or university located?', 'UK');
     $this->assertElementNotVisible('#edit-country-writein');
 
     // Graduate form testing.
@@ -86,19 +86,19 @@ public function testJavascriptStates() {
     $this->assertElementVisible('#edit-graduate');
     $this->assertElementNotVisible('#edit-average');
 
-    $this->assertFalse($driver->isChecked($this->cssSelect('#edit-info-provide')), '#edit-info-provide is not checked');
-    $driver->setValue($this->cssSelect('#edit-more-info'), 'Some text');
-    $this->assertTrue($driver->isChecked($this->cssSelect('#edit-info-provide')), '#edit-info-provide is checked');
-    // This is not working for some reason.
-    $driver->setValue($this->cssSelect('#edit-more-info'), NULL);
-    $this->assertJsCondition('!jQuery("#edit-more-info").val()');
-    $this->assertFalse($driver->isChecked($this->cssSelect('#edit-info-provide')), '#edit-info-provide is not checked');
+    $this->assertSession()->checkboxNotChecked('Check here if you have provided information above');
+    $page->fillField('Please describe your graduate studies', 'Some text');
+    $this->assertSession()->checkboxChecked('Check here if you have provided information above');
+    $page->fillField('Please describe your graduate studies', '');
+    // Empty and filled states are triggered on keyup event.
+    $page->findField('Please describe your graduate studies')->keyUp('a');
+    $this->assertSession()->checkboxNotChecked('Check here if you have provided information above');
 
     // Feedback testing.
     $this->assertElementNotVisible('#edit-feedback');
-    $this->click('#edit-expand-more-info');
+    $page->checkField('Check here if you want to add more information.');
     $this->assertElementVisible('#edit-feedback');
-    $this->click('#edit-expand-more-info');
+    $page->uncheckField('Check here if you want to add more information.');
     $this->assertElementNotVisible('#edit-feedback');
   }
 
diff --git a/core/tests/Drupal/FunctionalJavascriptTests/JavascriptTestBase.php b/core/tests/Drupal/FunctionalJavascriptTests/JavascriptTestBase.php
index 55c7f77..2862d4c 100644
--- a/core/tests/Drupal/FunctionalJavascriptTests/JavascriptTestBase.php
+++ b/core/tests/Drupal/FunctionalJavascriptTests/JavascriptTestBase.php
@@ -44,7 +44,7 @@ protected function initMink() {
    */
   protected function assertElementVisible($css_selector, $message = '') {
     $message = $message ?: "Element ($css_selector) is visible.";
-    $this->assertTrue($this->getSession()->getDriver()->isVisible($this->cssSelect($css_selector)), $message);
+    $this->assertTrue($this->getSession()->getDriver()->isVisible(CssSelector::toXPath($css_selector)), $message);
   }
 
   /**
@@ -57,7 +57,7 @@ protected function assertElementVisible($css_selector, $message = '') {
    */
   protected function assertElementNotVisible($css_selector, $message = '') {
     $message = $message ?: "Element ($css_selector) is not visible.";
-    $this->assertFalse($this->getSession()->getDriver()->isVisible($this->cssSelect($css_selector)), $message);
+    $this->assertFalse($this->getSession()->getDriver()->isVisible(CssSelector::toXPath($css_selector)), $message);
   }
 
   /**
diff --git a/core/tests/Drupal/Tests/BrowserTestBase.php b/core/tests/Drupal/Tests/BrowserTestBase.php
index a3fa3a7..8d8ea2b 100644
--- a/core/tests/Drupal/Tests/BrowserTestBase.php
+++ b/core/tests/Drupal/Tests/BrowserTestBase.php
@@ -20,7 +20,6 @@
 use Drupal\Core\StreamWrapper\StreamWrapperInterface;
 use Drupal\Core\Test\TestRunnerKernel;
 use Drupal\Core\Url;
-use Drupal\simpletest\AssertContentTrait;
 use Drupal\simpletest\RandomGeneratorTrait;
 use Drupal\simpletest\SessionTestTrait;
 use Drupal\simpletest\WebAssert;
@@ -45,7 +44,6 @@
    * @todo Move these into Drupal\Tests namespace and leave deprecated stubs
    *   in simpletest module. See https://www.drupal.org/node/2702281
    */
-  use AssertContentTrait;
   use RandomGeneratorTrait;
   use SessionTestTrait;