diff --git a/tests/phpunit/includes/functions.php b/tests/phpunit/includes/functions.php
index cc5469ca4e..d7c2ff47ab 100644
--- a/tests/phpunit/includes/functions.php
+++ b/tests/phpunit/includes/functions.php
@@ -2,6 +2,8 @@
 
 /**
  * Retrieves PHPUnit runner version.
+ *
+ * @return double The version number.
  */
 function tests_get_phpunit_version() {
 	if ( class_exists( 'PHPUnit_Runner_Version' ) ) {
@@ -134,6 +136,13 @@ function _delete_all_posts() {
 	}
 }
 
+/**
+ * Handles the WP die handler by outputting the given values as text.
+ *
+ * @param string $message The message.
+ * @param string $title   The title.
+ * @param array  $args    Array with arguments.
+ */
 function _wp_die_handler( $message, $title = '', $args = array() ) {
 	if ( ! $GLOBALS['_wp_die_disabled'] ) {
 		_wp_die_handler_txt( $message, $title, $args );
@@ -142,22 +151,45 @@ function _wp_die_handler( $message, $title = '', $args = array() ) {
 	}
 }
 
+/**
+ * Disables the WP die handler.
+ */
 function _disable_wp_die() {
 	$GLOBALS['_wp_die_disabled'] = true;
 }
 
+/**
+ * Enables the WP die handler.
+ */
 function _enable_wp_die() {
 	$GLOBALS['_wp_die_disabled'] = false;
 }
 
+/**
+ * Returns the die handler.
+ *
+ * @return string The die handler.
+ */
 function _wp_die_handler_filter() {
 	return '_wp_die_handler';
 }
 
+/**
+ * Returns the die handler.
+ *
+ * @return string The die handler.
+ */
 function _wp_die_handler_filter_exit() {
 	return '_wp_die_handler_exit';
 }
 
+/**
+ * Dies without an exit.
+ *
+ * @param string $message The message.
+ * @param string $title   The title.
+ * @param array  $args    Array with arguments.
+ */
 function _wp_die_handler_txt( $message, $title, $args ) {
 	echo "\nwp_die called\n";
 	echo "Message : $message\n";
@@ -170,6 +202,13 @@ function _wp_die_handler_txt( $message, $title, $args ) {
 	}
 }
 
+/**
+ * Dies with an exit.
+ *
+ * @param string $message The message.
+ * @param string $title   The title.
+ * @param array  $args    Array with arguments.
+ */
 function _wp_die_handler_exit( $message, $title, $args ) {
 	echo "\nwp_die called\n";
 	echo "Message : $message\n";
@@ -197,6 +236,8 @@ function _set_default_permalink_structure_for_tests() {
 
 /**
  * Helper used with the `upload_dir` filter to remove the /year/month sub directories from the uploads path and URL.
+ *
+ * @return array The altered array.
  */
 function _upload_dir_no_subdir( $uploads ) {
 	$subdir = $uploads['subdir'];
@@ -210,6 +251,8 @@ function _upload_dir_no_subdir( $uploads ) {
 
 /**
  * Helper used with the `upload_dir` filter to set https upload URL.
+ *
+ * @return array The altered array.
  */
 function _upload_dir_https( $uploads ) {
 	$uploads['url']     = str_replace( 'http://', 'https://', $uploads['url'] );
@@ -220,6 +263,8 @@ function _upload_dir_https( $uploads ) {
 
 /**
  * Use the Spy_REST_Server class for the REST server.
+ *
+ * @return string The server class name.
  */
 function _wp_rest_server_class_filter() {
 	return 'Spy_REST_Server';