diff --git a/core/tests/Drupal/FunctionalTests/AssertLegacyTrait.php b/core/tests/Drupal/FunctionalTests/AssertLegacyTrait.php
index ee139d9..33eea7f 100644
--- a/core/tests/Drupal/FunctionalTests/AssertLegacyTrait.php
+++ b/core/tests/Drupal/FunctionalTests/AssertLegacyTrait.php
@@ -205,7 +205,7 @@ protected function assertLink($label, $index = 0) {
   }
 
   /**
-   * Passes if a link with the specified label is found.
+   * Passes if a link with the specified label is not found.
    *
    * An optional link index may be passed.
    *
@@ -228,7 +228,7 @@ protected function assertNoLink($label) {
    *   Link position counting from zero.
    *
    * @deprecated Scheduled for removal in Drupal 9.0.0.
-   *   Use $this->assertSession()->LinkByHref() instead.
+   *   Use $this->assertSession()->linkByHref() instead.
    */
   protected function assertLinkByHref($href, $index = 0) {
     $this->assertSession()->linkByHrefExists($href, $index);
@@ -243,7 +243,7 @@ protected function assertLinkByHref($href, $index = 0) {
    *   Link position counting from zero.
    *
    * @deprecated Scheduled for removal in Drupal 9.0.0.
-   *   Use $this->assertSession()->LinkByHref() instead.
+   *   Use $this->assertSession()->linkByHrefNotExists() instead.
    */
   protected function assertNoLinkByHref($href, $index = 0) {
     $this->assertSession()->linkByHrefNotExists($href, $index);
@@ -332,7 +332,7 @@ protected function assertEscaped($raw) {
   }
 
   /**
-   * Passes if the raw text IS NOT found escaped on the loaded page, fail otherwise.
+   * Passes if the raw text is not found escaped on the loaded page.
    *
    * Raw text refers to the raw HTML that the page generated.
    *
diff --git a/core/tests/Drupal/Tests/WebAssert.php b/core/tests/Drupal/Tests/WebAssert.php
index 5c270d9..972d086 100644
--- a/core/tests/Drupal/Tests/WebAssert.php
+++ b/core/tests/Drupal/Tests/WebAssert.php
@@ -218,8 +218,6 @@ public function linkExists($label, $index = 0, $message = '') {
    *
    * @param string|\Drupal\Component\Render\MarkupInterface $label
    *   Text between the anchor tags.
-   * @param int $index
-   *   Link position counting from zero.
    * @param string $message
    *   (optional) A message to display with the assertion. Do not translate
    *   messages: use strtr() to embed variables in the message text, not
@@ -229,8 +227,6 @@ public function linkExists($label, $index = 0, $message = '') {
    *   Thrown when element doesn't exist, or the link label is a different one.
    */
   public function linkNotExists($label, $message = '') {
-    // Cast MarkupInterface objects to string.
-    $label = (string) $label;
     $message = ($message ? $message : strtr('Link with label %label found.', ['%label' => $label]));
     $links = $this->session->getPage()->findAll('named', ['link', $label]);
     $this->assert(empty($links), $message);
@@ -240,7 +236,7 @@ public function linkNotExists($label, $message = '') {
    * {@inheritdoc}
    */
   public function fieldValueEquals($field, $value, TraversableElement $container = NULL) {
-    parent::fieldValueEquals($field, (string) $value, $container);
+    parent::fieldValueEquals($field, $value, $container);
   }
 
   /**
@@ -260,7 +256,6 @@ public function fieldValueEquals($field, $value, TraversableElement $container =
    *   Thrown when element doesn't exist, or the link label is a different one.
    */
   public function linkByHrefExists($href, $index = 0, $message = '') {
-    // Cast MarkupInterface objects to string.
     $xpath = $this->buildXPathQuery('//a[contains(@href, :href)]', [':href' => $href]);
     $message = ($message ? $message : strtr('Link containing href %href found.', ['%href' => $href]));
     $links = $this->session->getPage()->findAll('xpath', $xpath);
@@ -316,7 +311,7 @@ public function buildXPathQuery($xpath, array $args = array()) {
     foreach ($args as $placeholder => $value) {
       // Cast MarkupInterface objects to string.
       if (is_object($value)) {
-        $value = (string) $value;
+        throw new \InvalidArgumentException('Just pass in scalar values.');
       }
       // XPath 1.0 doesn't support a way to escape single or double quotes in a
       // string literal. We split double quotes out of the string, and encode