diff --git a/core/modules/user/tests/src/Functional/UserRegistrationTest.php b/core/modules/user/tests/src/Functional/UserRegistrationTest.php
index 0a55dbbb0c..67711dcacc 100644
--- a/core/modules/user/tests/src/Functional/UserRegistrationTest.php
+++ b/core/modules/user/tests/src/Functional/UserRegistrationTest.php
@@ -56,8 +56,8 @@ public function testRegistrationWithEmailVerification() {
     $edit = [];
     $edit['name'] = $name = $this->randomMachineName();
     $edit['mail'] = $mail = $edit['name'] . '@example.com';
-    $this->drupalPostForm('user/register', $edit, $this->t('Create new account'));
-    $this->assertText($this->t('A welcome message with further instructions has been sent to your email address.'), 'User registered successfully.');
+    $this->submitForm('user/register', $edit, $this->t('Create new account'));
+    $this->assertSession()->responseContains($this->t('A welcome message with further instructions has been sent to your email address.'), 'User registered successfully.');
 
     /** @var EntityStorageInterface $storage */
     $storage = $this->container->get('entity_type.manager')->getStorage('user');
@@ -73,7 +73,7 @@ public function testRegistrationWithEmailVerification() {
     $edit = [];
     $edit['name'] = $name = $this->randomMachineName();
     $edit['mail'] = $mail = $edit['name'] . '@example.com';
-    $this->drupalPostForm('user/register', $edit, $this->t('Create new account'));
+    $this->submitForm('user/register', $edit, $this->t('Create new account'));
     $this->container->get('entity_type.manager')->getStorage('user')->resetCache();
     $accounts = $storage->loadByProperties(['name' => $name, 'mail' => $mail]);
     $new_user = reset($accounts);
@@ -99,19 +99,19 @@ public function testRegistrationWithoutEmailVerification() {
     // Try entering a mismatching password.
     $edit['pass[pass1]'] = '99999.0';
     $edit['pass[pass2]'] = '99999';
-    $this->drupalPostForm('user/register', $edit, $this->t('Create new account'));
-    $this->assertText($this->t('The specified passwords do not match.'), 'Typing mismatched passwords displays an error message.');
+    $this->submitForm('user/register', $edit, $this->t('Create new account'));
+    $this->assertSession()->responseContains($this->t('The specified passwords do not match.'), 'Typing mismatched passwords displays an error message.');
 
     // Enter a correct password.
     $edit['pass[pass1]'] = $new_pass = $this->randomMachineName();
     $edit['pass[pass2]'] = $new_pass;
-    $this->drupalPostForm('user/register', $edit, $this->t('Create new account'));
+    $this->submitForm('user/register', $edit, $this->t('Create new account'));
     $this->container->get('entity_type.manager')->getStorage('user')->resetCache();
     $accounts = $this->container->get('entity_type.manager')->getStorage('user')
       ->loadByProperties(['name' => $name, 'mail' => $mail]);
     $new_user = reset($accounts);
     $this->assertNotNull($new_user, 'New account successfully created with matching passwords.');
-    $this->assertText($this->t('Registration successful. You are now logged in.'), 'Users are logged in after registering.');
+    $this->assertSession()->responseContains($this->t('Registration successful. You are now logged in.'), 'Users are logged in after registering.');
     $this->drupalLogout();
 
     // Allow registration by site visitors, but require administrator approval.
@@ -121,16 +121,16 @@ public function testRegistrationWithoutEmailVerification() {
     $edit['mail'] = $mail = $edit['name'] . '@example.com';
     $edit['pass[pass1]'] = $pass = $this->randomMachineName();
     $edit['pass[pass2]'] = $pass;
-    $this->drupalPostForm('user/register', $edit, $this->t('Create new account'));
-    $this->assertText($this->t('Thank you for applying for an account. Your account is currently pending approval by the site administrator.'), 'Users are notified of pending approval');
+    $this->submitForm('user/register', $edit, $this->t('Create new account'));
+    $this->assertSession()->responseContains($this->t('Thank you for applying for an account. Your account is currently pending approval by the site administrator.'), 'Users are notified of pending approval');
 
     // Try to log in before administrator approval.
     $auth = [
       'name' => $name,
       'pass' => $pass,
     ];
-    $this->drupalPostForm('user/login', $auth, $this->t('Log in'));
-    $this->assertText($this->t('The username @name has not been activated or is blocked.', ['@name' => $name]), 'User cannot log in yet.');
+    $this->submitForm('user/login', $auth, $this->t('Log in'));
+    $this->assertSession()->responseContains($this->t('The username @name has not been activated or is blocked.', ['@name' => $name]), 'User cannot log in yet.');
 
     // Activate the new account.
     $accounts = $this->container->get('entity_type.manager')->getStorage('user')
@@ -141,12 +141,12 @@ public function testRegistrationWithoutEmailVerification() {
     $edit = [
       'status' => 1,
     ];
-    $this->drupalPostForm('user/' . $new_user->id() . '/edit', $edit, $this->t('Save'));
+    $this->submitForm('user/' . $new_user->id() . '/edit', $edit, $this->t('Save'));
     $this->drupalLogout();
 
     // Log in after administrator approval.
-    $this->drupalPostForm('user/login', $auth, $this->t('Log in'));
-    $this->assertText($this->t('Member for'), 'User can log in after administrator approval.');
+    $this->submitForm('user/login', $auth, $this->t('Log in'));
+    $this->assertSession()->responseContains($this->t('Member for'), 'User can log in after administrator approval.');
   }
 
   /**
@@ -169,8 +169,8 @@ public function testRegistrationWithPasswordSet() {
     $edit['pass[pass2]'] = $new_pass;
 
     // Create a new user.
-    $this->drupalPostForm('user/register', $edit, $this->t('Create new account'));
-    $this->assertText($this->t('A welcome message with further instructions has been sent to your email address.'), 'Send e-mail to user after registering.');
+    $this->submitForm('user/register', $edit, $this->t('Create new account'));
+    $this->assertSession()->responseContains($this->t('A welcome message with further instructions has been sent to your email address.'), 'Send e-mail to user after registering.');
 
     // Make sure the user is still blocked.
     $this->container->get('entity_type.manager')->getStorage('user')->resetCache();
@@ -185,18 +185,21 @@ public function testRegistrationWithPasswordSet() {
     $edit2 = [];
     $edit2['name'] = $name;
     $edit2['pass'] = $new_pass;
-    $this->drupalPostForm('user/login', $edit2, $this->t('Log in'));
-    $this->assertRaw($this->t('The username %name has not been activated or is blocked.', ['%name' => $name]), $this->t('User cannot login yet.'));
+    $this->submitForm('user/login', $edit2, $this->t('Log in'));
+    $this->assertSession()->responseContains($this->t('The username %name has not been activated or is blocked.', ['%name' => $name]), $this->t('User cannot login yet.'));
 
     // Try to activate the user.
     $_emails = $this->drupalGetMails();
+    $this->assertCount(2, $_emails);
     $email = end($_emails);
-    $one_time_link = [];
-    preg_match('@user/reset/[0-9]+/([0-9]+)/([a-zA-Z0-9_\-]+)\n@', $email['body'], $one_time_link);
+    $urls = [];
+    preg_match('#.+user/reset/.+#', $email['body'], $urls);
+
+    return $urls[0];
 
     $_uid = $new_user->id();
-    $this->drupalGet("user/reset/$_uid/$one_time_link[1]/$one_time_link[2]");
-    $this->assertText($this->t('You have just used your one-time login link. Your account is now active.'), $this->t('User account activated.'));
+    $this->drupalGet($urls[0]);
+    $this->assertSession()->responseContains($this->t('You have just used your one-time login link. Your account is now active.'), $this->t('User account activated.'));
   }
 
   /**
@@ -218,14 +221,14 @@ public function testRegistrationEmailDuplicates() {
     $edit['mail'] = $duplicate_user->getEmail();
 
     // Attempt to create a new account using an existing email address.
-    $this->drupalPostForm('user/register', $edit, $this->t('Create new account'));
-    $this->assertText($this->t('The email address @email is already taken.', ['@email' => $duplicate_user->getEmail()]), 'Supplying an exact duplicate email address displays an error message');
+    $this->submitForm('user/register', $edit, $this->t('Create new account'));
+    $this->assertSession()->responseContains($this->t('The email address @email is already taken.', ['@email' => $duplicate_user->getEmail()]), 'Supplying an exact duplicate email address displays an error message');
 
     // Attempt to bypass duplicate email validation by adding spaces.
     $edit['mail'] = '   ' . $duplicate_user->getEmail() . '   ';
 
-    $this->drupalPostForm('user/register', $edit, $this->t('Create new account'));
-    $this->assertText($this->t('The email address @email is already taken.', ['@email' => $duplicate_user->getEmail()]), 'Supplying a duplicate email address with added whitespace displays an error message');
+    $this->submitForm('user/register', $edit, $this->t('Create new account'));
+    $this->assertSession()->responseContains($this->t('The email address @email is already taken.', ['@email' => $duplicate_user->getEmail()]), 'Supplying a duplicate email address with added whitespace displays an error message');
   }
 
   /**
@@ -277,7 +280,7 @@ public function testUuidFormState() {
     $edit['pass[pass2]'] = $edit['pass[pass1]'] = $this->randomMachineName();
 
     // Create one account.
-    $this->drupalPostForm('user/register', $edit, $this->t('Create new account'));
+    $this->submitForm('user/register', $edit, $this->t('Create new account'));
     $this->assertSession()->statusCodeEquals(200);
 
     $user_storage = \Drupal::entityTypeManager()->getStorage('user');
@@ -290,7 +293,7 @@ public function testUuidFormState() {
     $edit['mail'] = $edit['name'] . '@example.com';
     $edit['pass[pass2]'] = $edit['pass[pass1]'] = $this->randomMachineName();
 
-    $this->drupalPostForm('user/register', $edit, $this->t('Create new account'));
+    $this->submitForm('user/register', $edit, $this->t('Create new account'));
     $this->assertSession()->statusCodeEquals(200);
 
     $this->assertNotEmpty($user_storage->loadByProperties(['name' => $edit['name']]));
@@ -322,20 +325,20 @@ public function testRegistrationDefaultValues() {
     $edit['mail'] = $mail = $edit['name'] . '@example.com';
     $edit['pass[pass1]'] = $new_pass = $this->randomMachineName();
     $edit['pass[pass2]'] = $new_pass;
-    $this->drupalPostForm(NULL, $edit, $this->t('Create new account'));
+    $this->submitForm(NULL, $edit, $this->t('Create new account'));
 
     // Check user fields.
     $accounts = $this->container->get('entity_type.manager')->getStorage('user')
       ->loadByProperties(['name' => $name, 'mail' => $mail]);
     $new_user = reset($accounts);
-    $this->assertEqual($new_user->getAccountName(), $name, 'Username matches.');
-    $this->assertEqual($new_user->getEmail(), $mail, 'Email address matches.');
+    $this->assertEquals($new_user->getAccountName(), $name, 'Username matches.');
+    $this->assertEquals($new_user->getEmail(), $mail, 'Email address matches.');
     $this->assertTrue(($new_user->getCreatedTime() > REQUEST_TIME - 20), 'Correct creation time.');
-    $this->assertEqual($new_user->isActive(), $config_user_settings->get('register') == UserInterface::REGISTER_VISITORS ? 1 : 0, 'Correct status field.');
-    $this->assertEqual($new_user->getTimezone(), $config_system_date->get('timezone.default'), 'Correct time zone field.');
-    $this->assertEqual($new_user->langcode->value, \Drupal::languageManager()->getDefaultLanguage()->getId(), 'Correct language field.');
-    $this->assertEqual($new_user->preferred_langcode->value, \Drupal::languageManager()->getDefaultLanguage()->getId(), 'Correct preferred language field.');
-    $this->assertEqual($new_user->init->value, $mail, 'Correct init field.');
+    $this->assertEquals($new_user->isActive(), $config_user_settings->get('register') == UserInterface::REGISTER_VISITORS ? 1 : 0, 'Correct status field.');
+    $this->assertEquals($new_user->getTimezone(), $config_system_date->get('timezone.default'), 'Correct time zone field.');
+    $this->assertEquals($new_user->langcode->value, \Drupal::languageManager()->getDefaultLanguage()->getId(), 'Correct language field.');
+    $this->assertEquals($new_user->preferred_langcode->value, \Drupal::languageManager()->getDefaultLanguage()->getId(), 'Correct preferred language field.');
+    $this->assertEquals($new_user->init->value, $mail, 'Correct init field.');
   }
 
   /**
@@ -351,12 +354,12 @@ public function testUniqueFields() {
       'mail' => 'test@example.com',
       'name' => $account->getAccountName(),
     ];
-    $this->drupalPostForm('user/register', $edit, $this->t('Create new account'));
-    $this->assertRaw(new FormattableMarkup('The username %value is already taken.', ['%value' => $account->getAccountName()]));
+    $this->submitForm('user/register', $edit, $this->t('Create new account'));
+    $this->assertSession()->responseContains(new FormattableMarkup('The username %value is already taken.', ['%value' => $account->getAccountName()]));
 
     $edit = ['mail' => $account->getEmail(), 'name' => $this->randomString()];
-    $this->drupalPostForm('user/register', $edit, $this->t('Create new account'));
-    $this->assertRaw(new FormattableMarkup('The email address %value is already taken.', ['%value' => $account->getEmail()]));
+    $this->submitForm('user/register', $edit, $this->t('Create new account'));
+    $this->assertSession()->responseContains(new FormattableMarkup('The email address %value is already taken.', ['%value' => $account->getEmail()]));
   }
 
   /**
@@ -390,7 +393,7 @@ public function testRegistrationWithUserFields() {
 
     // Check that the field does not appear on the registration form.
     $this->drupalGet('user/register');
-    $this->assertNoText($field->label(), 'The field does not appear on user registration form');
+    $this->assertSession()->responseNotContains($field->label(), 'The field does not appear on user registration form');
     $this->assertSession()->responseHeaderContains('X-Drupal-Cache-Tags', 'config:core.entity_form_display.user.user.register');
     $this->assertSession()->responseHeaderContains('X-Drupal-Cache-Tags', 'config:user.settings');
 
@@ -400,7 +403,7 @@ public function testRegistrationWithUserFields() {
       ->save();
 
     $this->drupalGet('user/register');
-    $this->assertText($field->label(), 'The field appears on user registration form');
+    $this->assertSession()->responseContains($field->label(), 'The field appears on user registration form');
     $this->assertRegistrationFormCacheTagsWithUserFields();
 
     // Check that validation errors are correctly reported.
@@ -409,24 +412,24 @@ public function testRegistrationWithUserFields() {
     $edit['mail'] = $mail = $edit['name'] . '@example.com';
     // Missing input in required field.
     $edit['test_user_field[0][value]'] = '';
-    $this->drupalPostForm(NULL, $edit, $this->t('Create new account'));
+    $this->submitForm(NULL, $edit, $this->t('Create new account'));
     $this->assertRegistrationFormCacheTagsWithUserFields();
-    $this->assertRaw($this->t('@name field is required.', ['@name' => $field->label()]));
+    $this->assertSession()->responseContains($this->t('@name field is required.', ['@name' => $field->label()]));
     // Invalid input.
     $edit['test_user_field[0][value]'] = '-1';
-    $this->drupalPostForm(NULL, $edit, $this->t('Create new account'));
+    $this->submitForm(NULL, $edit, $this->t('Create new account'));
     $this->assertRegistrationFormCacheTagsWithUserFields();
-    $this->assertRaw($this->t('%name does not accept the value -1.', ['%name' => $field->label()]));
+    $this->assertSession()->responseContains($this->t('%name does not accept the value -1.', ['%name' => $field->label()]));
 
     // Submit with valid data.
     $value = rand(1, 255);
     $edit['test_user_field[0][value]'] = $value;
-    $this->drupalPostForm(NULL, $edit, $this->t('Create new account'));
+    $this->submitForm(NULL, $edit, $this->t('Create new account'));
     // Check user fields.
     $accounts = $this->container->get('entity_type.manager')->getStorage('user')
       ->loadByProperties(['name' => $name, 'mail' => $mail]);
     $new_user = reset($accounts);
-    $this->assertEqual($new_user->test_user_field->value, $value, 'The field value was correctly saved.');
+    $this->assertEquals($new_user->test_user_field->value, $value, 'The field value was correctly saved.');
 
     // Check that the 'add more' button works.
     $field_storage->setCardinality(FieldStorageDefinitionInterface::CARDINALITY_UNLIMITED);
@@ -437,21 +440,21 @@ public function testRegistrationWithUserFields() {
     $value = rand(1, 255);
     $edit = [];
     $edit['test_user_field[0][value]'] = $value;
-    $this->drupalPostForm(NULL, $edit, $this->t('Add another item'));
-    $this->drupalPostForm(NULL, $edit, $this->t('Add another item'));
+    $this->submitForm(NULL, $edit, $this->t('Add another item'));
+    $this->submitForm(NULL, $edit, $this->t('Add another item'));
     // Submit with three values.
     $edit['test_user_field[1][value]'] = $value + 1;
     $edit['test_user_field[2][value]'] = $value + 2;
     $edit['name'] = $name = $this->randomMachineName();
     $edit['mail'] = $mail = $edit['name'] . '@example.com';
-    $this->drupalPostForm(NULL, $edit, $this->t('Create new account'));
+    $this->submitForm(NULL, $edit, $this->t('Create new account'));
     // Check user fields.
     $accounts = $this->container->get('entity_type.manager')->getStorage('user')
       ->loadByProperties(['name' => $name, 'mail' => $mail]);
     $new_user = reset($accounts);
-    $this->assertEqual($new_user->test_user_field[0]->value, $value, 'The field value was correctly saved.');
-    $this->assertEqual($new_user->test_user_field[1]->value, $value + 1, 'The field value was correctly saved.');
-    $this->assertEqual($new_user->test_user_field[2]->value, $value + 2, 'The field value was correctly saved.');
+    $this->assertEquals($new_user->test_user_field[0]->value, $value, 'The field value was correctly saved.');
+    $this->assertEquals($new_user->test_user_field[1]->value, $value + 1, 'The field value was correctly saved.');
+    $this->assertEquals($new_user->test_user_field[2]->value, $value + 2, 'The field value was correctly saved.');
   }
 
   /**