diff --git a/core/modules/simpletest/src/WebTestBase.php b/core/modules/simpletest/src/WebTestBase.php
index 347ddb3ed7f208fb2848048977e19932645599f1..9bf6c23e0b653fde327cf8afdf62c35133e717d7 100644
--- a/core/modules/simpletest/src/WebTestBase.php
+++ b/core/modules/simpletest/src/WebTestBase.php
@@ -404,7 +404,7 @@ protected function drupalBuildEntityView(EntityInterface $entity, $view_mode = '
    *   @endcode
    *   The following defaults are provided:
    *   - label: Random string.
-   *   - id: Random string.
+   *   - ID: Random string.
    *   - region: 'sidebar_first'.
    *   - theme: The default theme.
    *   - visibility: Empty array.
@@ -3147,7 +3147,9 @@ protected function assertThemeOutput($callback, array $variables = array(), $exp
    * @param $xpath
    *   XPath used to find the field.
    * @param $value
-   *   (optional) Value of the field to assert.
+   *   (optional) Value of the field to assert. You may pass in NULL (default)
+   *   to skip checking the actual value, while still checking that the field
+   *   exists.
    * @param $message
    *   (optional) A message to display with the assertion. Do not translate
    *   messages: use format_string() to embed variables in the message text, not
@@ -3222,12 +3224,13 @@ protected function getSelectedItem(\SimpleXMLElement $element) {
   }
 
   /**
-   * Asserts that a field does not exist in the current page by the given XPath.
+   * Asserts that a field doesn't exist or its value doesn't match, by XPath.
    *
    * @param $xpath
    *   XPath used to find the field.
    * @param $value
-   *   (optional) Value of the field to assert.
+   *   (optional) Value for the field, to assert that the field's value on the
+   *   page doesn't match it.
    * @param $message
    *   (optional) A message to display with the assertion. Do not translate
    *   messages: use format_string() to embed variables in the message text, not
@@ -3265,7 +3268,9 @@ protected function assertNoFieldByXPath($xpath, $value = NULL, $message = '', $g
    * @param $name
    *   Name of field to assert.
    * @param $value
-   *   Value of the field to assert.
+   *   (optional) Value of the field to assert. You may pass in NULL (default)
+   *   to skip checking the actual value, while still checking that the field
+   *   exists.
    * @param $message
    *   (optional) A message to display with the assertion. Do not translate
    *   messages: use format_string() to embed variables in the message text, not
@@ -3302,7 +3307,10 @@ protected function assertFieldByName($name, $value = NULL, $message = NULL, $gro
    * @param $name
    *   Name of field to assert.
    * @param $value
-   *   Value of the field to assert.
+   *   (optional) Value for the field, to assert that the field's value on the
+   *   page doesn't match it. You may pass in NULL to skip checking the
+   *   value, while still checking that the field doesn't exist. However, the
+   *   default value ('') asserts that the field value is not an empty string.
    * @param $message
    *   (optional) A message to display with the assertion. Do not translate
    *   messages: use format_string() to embed variables in the message text, not
@@ -3321,12 +3329,15 @@ protected function assertNoFieldByName($name, $value = '', $message = '', $group
   }
 
   /**
-   * Asserts that a field exists with the given id and value.
+   * Asserts that a field exists with the given ID and value.
    *
    * @param $id
-   *   Id of field to assert.
+   *   ID of field to assert.
    * @param $value
-   *   Value of the field to assert.
+   *   (optional) Value for the field to assert. You may pass in NULL to skip
+   *   checking the value, while still checking that the field exists.
+   *   However, the default value ('') asserts that the field value is an empty
+   *   string.
    * @param $message
    *   (optional) A message to display with the assertion. Do not translate
    *   messages: use format_string() to embed variables in the message text, not
@@ -3345,12 +3356,15 @@ protected function assertFieldById($id, $value = '', $message = '', $group = 'Br
   }
 
   /**
-   * Asserts that a field does not exist with the given id and value.
+   * Asserts that a field does not exist with the given ID and value.
    *
    * @param $id
-   *   Id of field to assert.
+   *   ID of field to assert.
    * @param $value
-   *   Value of the field to assert.
+   *   (optional) Value for the field, to assert that the field's value on the
+   *   page doesn't match it. You may pass in NULL to skip checking the value,
+   *   while still checking that the field doesn't exist. However, the default
+   *   value ('') asserts that the field value is not an empty string.
    * @param $message
    *   (optional) A message to display with the assertion. Do not translate
    *   messages: use format_string() to embed variables in the message text, not
@@ -3372,7 +3386,7 @@ protected function assertNoFieldById($id, $value = '', $message = '', $group = '
    * Asserts that a checkbox field in the current page is checked.
    *
    * @param $id
-   *   Id of field to assert.
+   *   ID of field to assert.
    * @param $message
    *   (optional) A message to display with the assertion. Do not translate
    *   messages: use format_string() to embed variables in the message text, not
@@ -3395,7 +3409,7 @@ protected function assertFieldChecked($id, $message = '', $group = 'Browser') {
    * Asserts that a checkbox field in the current page is not checked.
    *
    * @param $id
-   *   Id of field to assert.
+   *   ID of field to assert.
    * @param $message
    *   (optional) A message to display with the assertion. Do not translate
    *   messages: use format_string() to embed variables in the message text, not
@@ -3418,7 +3432,7 @@ protected function assertNoFieldChecked($id, $message = '', $group = 'Browser')
    * Asserts that a select option in the current page exists.
    *
    * @param $id
-   *   Id of select field to assert.
+   *   ID of select field to assert.
    * @param $option
    *   Option to assert.
    * @param $message
@@ -3443,7 +3457,7 @@ protected function assertOption($id, $option, $message = '', $group = 'Browser')
    * Asserts that a select option in the current page does not exist.
    *
    * @param $id
-   *   Id of select field to assert.
+   *   ID of select field to assert.
    * @param $option
    *   Option to assert.
    * @param $message
@@ -3469,7 +3483,7 @@ protected function assertNoOption($id, $option, $message = '', $group = 'Browser
    * Asserts that a select option in the current page is checked.
    *
    * @param $id
-   *   Id of select field to assert.
+   *   ID of select field to assert.
    * @param $option
    *   Option to assert.
    * @param $message
@@ -3496,7 +3510,7 @@ protected function assertOptionSelected($id, $option, $message = '', $group = 'B
    * Asserts that a select option in the current page is not checked.
    *
    * @param $id
-   *   Id of select field to assert.
+   *   ID of select field to assert.
    * @param $option
    *   Option to assert.
    * @param $message
@@ -3518,10 +3532,10 @@ protected function assertNoOptionSelected($id, $option, $message = '', $group =
   }
 
   /**
-   * Asserts that a field exists with the given name or id.
+   * Asserts that a field exists with the given name or ID.
    *
    * @param $field
-   *   Name or id of field to assert.
+   *   Name or ID of field to assert.
    * @param $message
    *   (optional) A message to display with the assertion. Do not translate
    *   messages: use format_string() to embed variables in the message text, not
@@ -3540,10 +3554,10 @@ protected function assertField($field, $message = '', $group = 'Other') {
   }
 
   /**
-   * Asserts that a field does not exist with the given name or id.
+   * Asserts that a field does not exist with the given name or ID.
    *
    * @param $field
-   *   Name or id of field to assert.
+   *   Name or ID of field to assert.
    * @param $message
    *   (optional) A message to display with the assertion. Do not translate
    *   messages: use format_string() to embed variables in the message text, not