diff --git a/WordPress/Tests/NamingConventions/PrefixAllGlobalsUnitTest.1.inc b/WordPress/Tests/NamingConventions/PrefixAllGlobalsUnitTest.1.inc
index 011e250b7f..707468c137 100644
--- a/WordPress/Tests/NamingConventions/PrefixAllGlobalsUnitTest.1.inc
+++ b/WordPress/Tests/NamingConventions/PrefixAllGlobalsUnitTest.1.inc
@@ -260,10 +260,10 @@ $GLOBALS[ $something ] = 'value'; // Warning.
 $GLOBALS[ "{$something}_something" ] = 'value'; // Warning.
 $GLOBALS[ ${$something} ] = 'value'; // Warning.
 
-define( ${$something}, 'value' ); // Warning.
+DEFINE( ${$something}, 'value' ); // Warning.
 define( $something, 'value' ); // Warning.
 define( $something . '_CONSTANT', 'value' ); // Warning.
-define( "{$something}_CONSTANT", 'value' ); // Warning.
+\Define( "{$something}_CONSTANT", 'value' ); // Warning.
 define( $something . '_CONSTANT', 'value' ); // Warning.
 
 do_action( "{$acronym_filter_var}_hook_name" ); // Warning.
@@ -683,4 +683,16 @@ class Acronym_AsymmetricVisibilityProperties {
     public function __construct(public protected(set) int $foo = 0) {} // Ok.
 }
 
+/*
+ * Safeguard correct handling of all types of namespaced function calls.
+ */
+\define('SOME_GLOBAL', [ 1, 2, 3 ]); // Bad.
+MyNamespace\define('SOME_GLOBAL', [ 1, 2, 3 ]); // Ok.
+\MyNamespace\define('SOME_GLOBAL', [ 1, 2, 3 ]); // Ok.
+namespace\define('SOME_GLOBAL', [ 1, 2, 3 ]); // Ok. The sniff should start flagging this once it can resolve relative namespaces.
+\do_action( 'plugin_action' ); // Bad.
+MyNamespace\do_action( 'plugin_action' ); // Ok.
+\MyNamespace\apply_filters( 'plugin_filter', $variable ); // Ok.
+namespace\do_action_ref_array( 'plugin_action', array( $variable ) ); // Ok. The sniff should start flagging this once it can resolve relative namespaces.
+
 // phpcs:set WordPress.NamingConventions.PrefixAllGlobals prefixes[]
diff --git a/WordPress/Tests/NamingConventions/PrefixAllGlobalsUnitTest.3.inc b/WordPress/Tests/NamingConventions/PrefixAllGlobalsUnitTest.3.inc
index be1eb3627f..e910701dba 100644
--- a/WordPress/Tests/NamingConventions/PrefixAllGlobalsUnitTest.3.inc
+++ b/WordPress/Tests/NamingConventions/PrefixAllGlobalsUnitTest.3.inc
@@ -12,7 +12,7 @@ class Some_Test extends \PHPUnit_Framework_TestCase {
 	}
 }
 
-$acronym_test = new class extends \PHPUnit_Framework_TestCase {
+$acronym_test = new class extends \phpunit_framework_testcase {
 
 	public function testPass() {
 		define( 'SOME_GLOBAL', '4.0.0' );
@@ -21,4 +21,36 @@ $acronym_test = new class extends \PHPUnit_Framework_TestCase {
 	}
 };
 
+// Test namespace resolution when the sniff checks the extending class.
+class Extends_Namespaced_Class_Not_WP_Test extends WP_Font_Face_UnitTestCase {
+
+    public function testPass() {
+        do_action( 'some-action', $something );
+    }
+}
+
+/*
+ * Safeguard correct handling of namespaced extending classes.
+ */
+class Extends_Partially_Qualified_Not_WP_Test extends MyNamespace\WP_UnitTestCase_Base {
+
+    public function testPass() {
+        do_action( 'some-action', $something );
+    }
+}
+
+class Extends_Fully_Qualified_Not_WP_Test extends \MyNamespace\WP_Ajax_UnitTestCase {
+
+    public function testPass() {
+        do_action( 'some-action', $something );
+    }
+}
+
+class Extends_Relative_Namespace_Not_WP_Test extends namespace\WP_Canonical_UnitTestCase {
+
+    public function testPass() {
+        do_action( 'some-action', $something );
+    }
+}
+
 // phpcs:set WordPress.NamingConventions.PrefixAllGlobals prefixes[]
diff --git a/WordPress/Tests/NamingConventions/PrefixAllGlobalsUnitTest.php b/WordPress/Tests/NamingConventions/PrefixAllGlobalsUnitTest.php
index b9beb09ff6..b93ad6216d 100644
--- a/WordPress/Tests/NamingConventions/PrefixAllGlobalsUnitTest.php
+++ b/WordPress/Tests/NamingConventions/PrefixAllGlobalsUnitTest.php
@@ -96,6 +96,16 @@ public function getErrorList( $testFile = 'PrefixAllGlobalsUnitTest.1.inc' ) {
 					616 => 1,
 					617 => 1,
 					633 => 1,
+					689 => 1,
+					693 => 1,
+				);
+
+			case 'PrefixAllGlobalsUnitTest.3.inc':
+				return array(
+					28 => 1,
+					38 => 1,
+					45 => 1,
+					52 => 1,
 				);
 
 			case 'PrefixAllGlobalsUnitTest.4.inc':
@@ -106,8 +116,6 @@ public function getErrorList( $testFile = 'PrefixAllGlobalsUnitTest.1.inc' ) {
 
 			case 'PrefixAllGlobalsUnitTest.2.inc':
 				// Namespaced - all OK, fall through to the default case.
-			case 'PrefixAllGlobalsUnitTest.3.inc':
-				// Test class - non-prefixed constant is fine, fall through to the default case.
 			default:
 				return array();
 		}
diff --git a/WordPress/Tests/NamingConventions/ValidHookNameUnitTest.1.inc b/WordPress/Tests/NamingConventions/ValidHookNameUnitTest.1.inc
index 830c3552d6..466c23e522 100644
--- a/WordPress/Tests/NamingConventions/ValidHookNameUnitTest.1.inc
+++ b/WordPress/Tests/NamingConventions/ValidHookNameUnitTest.1.inc
@@ -6,9 +6,9 @@ prefix_do_action( 'someAction' ); // Ok - not WP do_action.
 
 // Check for incorrect word separators.
 do_action( "admin_head-$hook_suffix" ); // Warning - use underscore.
-do_action( 'admin_head.media.upload_popup' ); // Warning - use underscore.
+DO_ACTION( 'admin_head.media.upload_popup' ); // Warning - use underscore.
 apply_filters( "bulk_actions {$this->screen->id}", $this->_actions ); // Warning - use underscore.
-apply_filters( "current_theme/supports-{$feature}", true, $args, $_wp_theme_features[$feature] ); // Warning - use underscore.
+\Apply_Filters( "current_theme/supports-{$feature}", true, $args, $_wp_theme_features[$feature] ); // Warning - use underscore.
 
 // Simple strings.
 do_action( "adminHead" ); // Error - use lowercase.
@@ -121,3 +121,14 @@ do_action( 'admin_head_' .  $fn( 'UPPERCASE', 'wrong-delimiter' ) . '_action' );
 do_action_ref_array( hook: 'My-Hook', args: $args ); // OK. Well, not really, but using the wrong parameter name, so not our concern.
 do_action_ref_array( args: $args, hook_name: 'my_hook', ); // OK.
 do_action_ref_array( args: $args, hook_name: 'My-Hook', ); // Error - use lowercase + warning about dash.
+
+/*
+ * Safeguard correct handling of all types of namespaced function calls.
+ */
+\apply_filters( 'adminHead', $variable ); // Error.
+MyNamespace\do_action( 'adminHead' ); // Ok.
+\MyNamespace\do_action_ref_array( 'adminHead', array( $variable ) ); // Ok.
+namespace\apply_filters_ref_array( 'adminHead', array( $variable ) ); // Ok. The sniff should start flagging this once it can resolve relative namespaces.
+apply_filters( 'admin_head_' .  MyNamespace\my_function('UPPERCASE') . '_action', $variable ); // Ok.
+do_action( 'admin_head_' .  \MyNamespace\my_function('UPPERCASE') . '_action' ); // Ok.
+do_action_ref_array( 'admin_head_' .  namespace\my_function('UPPERCASE') . '_action', array( $variable ) ); // Ok.
diff --git a/WordPress/Tests/NamingConventions/ValidHookNameUnitTest.php b/WordPress/Tests/NamingConventions/ValidHookNameUnitTest.php
index aac97da195..98649fb620 100644
--- a/WordPress/Tests/NamingConventions/ValidHookNameUnitTest.php
+++ b/WordPress/Tests/NamingConventions/ValidHookNameUnitTest.php
@@ -75,6 +75,7 @@ public function getErrorList( $testFile = 'ValidHookNameUnitTest.1.inc' ) {
 					114 => 1,
 					115 => 1,
 					123 => 1,
+					128 => 1,
 				);
 
 			case 'ValidHookNameUnitTest.2.inc':
diff --git a/WordPress/Tests/PHP/NoSilencedErrorsUnitTest.inc b/WordPress/Tests/PHP/NoSilencedErrorsUnitTest.inc
index f007d150bd..27b3598537 100644
--- a/WordPress/Tests/PHP/NoSilencedErrorsUnitTest.inc
+++ b/WordPress/Tests/PHP/NoSilencedErrorsUnitTest.inc
@@ -12,7 +12,7 @@ if (@in_array($array, $needle)) { // Bad.
 }
 
 // File extension.
-if ( @&file_exists( $filename ) && @ /*comment*/ is_readable( $filename ) ) {
+if ( @&file_exists( $filename ) && @ /*comment*/ IS_READABLE( $filename ) ) {
 	$file = @ \file( $filename );
 }
 
@@ -22,7 +22,7 @@ $fp = @fopen('https://www.example.com', 'r', false);
 
 // Directory extension.
 if (@is_dir($dir)) {
-    if ($dh = @\opendir($dir)) {
+    if ($dh = @\OPENDIR($dir)) {
         while (($file = @readdir($dh)) !== false) { // Bad.
             echo "filename: $file : filetype: " . @\filetype($dir . $file) . "\n";
         }
@@ -84,3 +84,11 @@ $decoded = @hex2bin( $data );
 // phpcs:set WordPress.PHP.NoSilencedErrors context_length 0
 echo @some_userland_function( $param ); // Bad.
 // phpcs:set WordPress.PHP.NoSilencedErrors context_length 6
+
+/*
+ * Safeguard correct handling of namespaced function calls (fully qualified is already tested above).
+ */
+$file = @MyNS\MyClass::file_get_contents( $file ); // Bad.
+$file = @MyNS\MyClass\file_exists( $file ); // Bad.
+$file = @namespace\MyNS\MyClass::file( $file ); // Bad.
+$file = @namespace\is_dir( $dir ); // The sniff should stop flagging this once it can resolve relative namespaces.
diff --git a/WordPress/Tests/PHP/NoSilencedErrorsUnitTest.php b/WordPress/Tests/PHP/NoSilencedErrorsUnitTest.php
index 7a576b992c..038c2c8d71 100644
--- a/WordPress/Tests/PHP/NoSilencedErrorsUnitTest.php
+++ b/WordPress/Tests/PHP/NoSilencedErrorsUnitTest.php
@@ -61,6 +61,10 @@ public function getWarningList() {
 			71 => 1,
 			78 => 1,
 			85 => 1,
+			91 => 1,
+			92 => 1,
+			93 => 1,
+			94 => 1,
 		);
 	}
 }
diff --git a/WordPress/Tests/Security/NonceVerificationUnitTest.1.inc b/WordPress/Tests/Security/NonceVerificationUnitTest.1.inc
index aee51ae39a..fc688e09de 100644
--- a/WordPress/Tests/Security/NonceVerificationUnitTest.1.inc
+++ b/WordPress/Tests/Security/NonceVerificationUnitTest.1.inc
@@ -250,7 +250,7 @@ function allow_for_unslash_before_noncecheck() {
 }
 
 function allow_for_unslash_in_sanitization() {
-	$var = sanitize_text_field( wp_unslash( $_POST['foo'] ) ); // OK.
+	$var = sanitize_text_field( WP_UNSLASH( $_POST['foo'] ) ); // OK.
 	wp_verify_nonce( $var );
 	echo $var;
 }
@@ -314,7 +314,7 @@ function allow_in_array_key_exists_before_noncecheck() {
 }
 
 function allow_in_key_exists_before_noncecheck() {
-	if (key_exists('foo', $_POST['subset']) === false) { // OK.
+	if (Key_Exists('foo', $_POST['subset']) === false) { // OK.
 		return;
 	}
 
@@ -369,7 +369,7 @@ function disallow_for_non_array_comparison_in_condition() {
 }
 
 function allow_for_array_comparison_in_condition_with_named_params() {
-	if ( array_keys( filter_value: 'my_action', array: $_GET['actions'], strict: true, ) ) { // OK.
+	if ( \array_KEYS( filter_value: 'my_action', array: $_GET['actions'], strict: true, ) ) { // OK.
 		check_admin_referer( 'foo' );
 		foo();
 	}
@@ -524,3 +524,168 @@ function different_function_name() {
     update_post_meta( (int) $_POST['id'], 'a_key', $_POST['a_value'] );
 }
 // phpcs:set WordPress.Security.NonceVerification customNonceVerificationFunctions[]
+
+function test_fully_qualified_call_to_global_nonce_verification_function() {
+    if ( ! IS_NUMERIC( $_POST['foo'] ) ) { // OK.
+        return;
+    }
+
+    \wp_verify_nonce( 'some_action' );
+}
+
+function test_namespace_relative_call_to_global_nonce_verification_function() {
+	if ( ! IS_NUMERIC( $_POST['foo'] ) ) { // Bad, but should become ok once the sniff is able to resolve relative namespaces.
+		return;
+	}
+
+	namespace\wp_verify_nonce( 'some_action' );
+}
+
+function test_namespaced_calls_to_incorrect_nonce_verification_functions() {
+    if ( ! is_numeric( $_POST['foo'] ) ) { // Bad - none of the below are the WP global functions, so no nonce verification.
+        return;
+    }
+
+    MyNamespace\wp_verify_nonce( 'some_action' );
+    \MyNamespace\check_admin_referer( 'some_action' );
+    namespace\Sub\check_ajax_referer( 'some_action' );
+}
+
+// phpcs:set WordPress.Security.NonceVerification customNonceVerificationFunctions[] my_nonce_check
+
+function test_namespace_relative_call_to_custom_nonce_verification_function() {
+	if ( ! is_int( $_POST['foo'] ) ) { // Bad, but should become ok once the sniff is able to resolve relative namespaces.
+		return;
+	}
+
+	namespace\my_nonce_check( 'some_action' );
+}
+
+function test_namespaced_calls_to_incorrect_custom_nonce_verification_functions() {
+	if ( ! is_string( $_POST['foo'] ) ) { // Bad - none of the below are a custom nonce verification function.
+		return;
+	}
+
+	MyNamespace\my_nonce_check( 'some_action' );
+	\MyNamespace\my_nonce_check( 'some_action' );
+	namespace\Sub\my_nonce_check( 'some_action' );
+}
+
+// phpcs:set WordPress.Security.NonceVerification customNonceVerificationFunctions[]
+
+function allow_fully_qualified_key_exists_functions() {
+    if ( \array_key_exists('foo', $_POST) === false ) { // OK.
+        return;
+    }
+
+    \WP_VERIFY_NONCE( 'some_action' );
+}
+
+function allow_fully_qualified_key_exists_functions_with_mixed_case() {
+	if ( \Key_Exists('foo', $_POST) === false ) { // OK.
+		return;
+	}
+
+	wp_verify_nonce( 'some_action' );
+}
+
+function allow_namespace_relative_call_to_global_key_exists_functions() {
+	if ( namespace\array_key_exists('foo', $_POST) === false ) { // Bad, but should become ok once the sniff is able to resolve relative namespaces.
+		return;
+	}
+
+	wp_verify_nonce( 'some_action' );
+}
+
+function disallow_namespaced_key_exists_functions() {
+    if ( MyNamespace\array_key_exists( 'foo', $_POST ) === false // Bad.
+        || \MyNamespace\key_exists( 'foo', $_POST ) === false // Bad.
+        || namespace\Sub\key_exists( 'foo', $_POST ) === false // Bad.
+    ) {
+        return;
+    }
+
+    wp_verify_nonce( 'some_action' );
+}
+
+function allow_fully_qualified_type_test_functions() {
+    if ( ! \is_numeric( $_POST['foo'] ) ) { // OK.
+        return;
+    }
+
+    \wp_verify_nonce( 'some_action' );
+}
+
+function allow_fully_qualified_type_test_functions_uppercase() {
+	if ( ! \IS_int( $_POST['foo'] ) ) { // OK.
+		return;
+	}
+
+	\wp_verify_nonce( 'some_action' );
+}
+
+function allow_namespace_relative_call_to_global_type_test_functions() {
+	if ( ! namespace\is_numeric( $_POST['foo'] ) ) { // Bad, but should become ok once the sniff is able to resolve relative namespaces.
+		return;
+	}
+
+	\wp_verify_nonce( 'some_action' );
+}
+
+function disallow_namespaced_type_test_functions() {
+    if ( ! MyNamespace\is_bool( $_POST['foo'] ) // Bad.
+        || ! \MyNamespace\is_object( $_POST['foo'] ) // Bad.
+        || ! namespace\Sub\is_string( $_POST['foo'] ) ) // Bad.
+    {
+        return;
+    }
+
+    \wp_verify_nonce( 'some_action' );
+}
+
+function allow_fully_qualified_array_comparison_functions() {
+    if ( \in_array( $_GET['action'], $valid_actions, true ) ) { // OK.
+        check_admin_referer( 'foo' );
+    }
+}
+
+function allow_namespace_relative_call_to_global_array_comparison_functions() {
+	if ( namespace\in_array( $_GET['action'], $valid_actions, true ) ) { // Bad, but should become ok once the sniff is able to resolve relative namespaces.
+		check_admin_referer( 'foo' );
+	}
+}
+
+function disallow_namespaced_array_comparison_functions() {
+    if ( MyNamespace\in_array( $_GET['action'], $valid_actions, true ) // Bad.
+        || \MyNamespace\array_search( array( 'subscribe', 'unsubscribe' ), $_GET['action'], true ) // Bad.
+        || namespace\Sub\array_keys( $_GET['actions'], 'my_action', true ) // Bad.
+    ) {
+        check_admin_referer( 'foo' );
+    }
+}
+
+function allow_fully_qualified_unslashing_functions() {
+    $var = \stripslashes_from_strings_only( $_POST['foo'] ); // OK.
+    wp_verify_nonce( $var );
+    echo $var;
+}
+
+function allow_fully_qualified_unslashing_functions_mixed_case() {
+	$var = \stripslashes_FROM_strings_ONLY( $_POST['foo'] ); // OK.
+	wp_verify_nonce( $var );
+	echo $var;
+}
+
+function allow_namespace_relative_call_to_global_unslashing_functions() {
+	$var = namespace\stripslashes_from_strings_only( $_POST['foo'] ); // Bad, but should become ok once the sniff is able to resolve relative namespaces.
+	wp_verify_nonce( $var );
+	echo $var;
+}
+
+function disallow_namespaced_unslashing_functions() {
+    $var = MyNamespace\stripslashes_from_strings_only( $_POST['foo'] ); // Bad.
+    $var = \MyNamespace\stripslashes_deep( $_POST['foo'] ); // Bad.
+    $var = namespace\Sub\wp_unslash( $_POST['foo'] ); // Bad.
+    wp_verify_nonce( $var );
+    echo $var;
+}
diff --git a/WordPress/Tests/Security/NonceVerificationUnitTest.php b/WordPress/Tests/Security/NonceVerificationUnitTest.php
index aa5e832e83..ea76b5a4b0 100644
--- a/WordPress/Tests/Security/NonceVerificationUnitTest.php
+++ b/WordPress/Tests/Security/NonceVerificationUnitTest.php
@@ -75,6 +75,22 @@ public function getErrorList( $testFile = '' ) {
 					470 => 1,
 					478 => 1,
 					524 => 2,
+					537 => 1,
+					545 => 1,
+					557 => 1,
+					565 => 1,
+					593 => 1,
+					601 => 1,
+					602 => 1,
+					603 => 1,
+					628 => 1,
+					636 => 1,
+					637 => 1,
+					638 => 1,
+					680 => 1,
+					686 => 1,
+					687 => 1,
+					688 => 1,
 				);
 
 			case 'NonceVerificationUnitTest.2.inc':
@@ -107,6 +123,10 @@ public function getWarningList( $testFile = '' ) {
 				return array(
 					365 => 1,
 					379 => 1,
+					653 => 1,
+					659 => 1,
+					660 => 1,
+					661 => 1,
 				);
 
 			case 'NonceVerificationUnitTest.4.inc':
diff --git a/WordPress/Tests/Utils/I18nTextDomainFixerUnitTest.4.inc b/WordPress/Tests/Utils/I18nTextDomainFixerUnitTest.4.inc
index d33d0a18e0..26f6cdd71f 100644
--- a/WordPress/Tests/Utils/I18nTextDomainFixerUnitTest.4.inc
+++ b/WordPress/Tests/Utils/I18nTextDomainFixerUnitTest.4.inc
@@ -77,11 +77,11 @@ is_textdomain_loaded( 'some-other-plugin' );
  * Incorrect text domain, should be replaced.
  */
 load_textdomain( 'text-domain', '/path/to/file.mo' );
-load_plugin_textdomain( 'text-domain', false, '/languages/' );
+\load_plugin_textdomain( 'text-domain', false, '/languages/' );
 load_muplugin_textdomain( 'other-text-domain', '/languages/' );
 load_theme_textdomain( 'third-text-domain', '/path/to/languages/' );
 load_child_theme_textdomain( 'text-domain', '/path/to/languages/' );
-unload_textdomain( 'text-domain' );
+unload_TEXTDOMAIN( 'text-domain' );
 
 __( $text, 'text-domain' );
 _e( $text, 'text-domain' );
@@ -281,5 +281,13 @@ __ (
     $args
 );
 
+/*
+ * Safeguard correct handling of namespaced function calls (partially qualified is already tested above).
+ */
+\MyNamespace\load_textdomain( 'text-domain', '/path/to/file.mo' );
+namespace\__( $text, 'text-domain' );
+\ESC_HTML__( $text, 'text-domain' );
+\get_translations_for_domain();
+
 // phpcs:set WordPress.Utils.I18nTextDomainFixer old_text_domain[]
 // phpcs:set WordPress.Utils.I18nTextDomainFixer new_text_domain false
diff --git a/WordPress/Tests/Utils/I18nTextDomainFixerUnitTest.4.inc.fixed b/WordPress/Tests/Utils/I18nTextDomainFixerUnitTest.4.inc.fixed
index f7fd2c6f4e..98f6adabfd 100644
--- a/WordPress/Tests/Utils/I18nTextDomainFixerUnitTest.4.inc.fixed
+++ b/WordPress/Tests/Utils/I18nTextDomainFixerUnitTest.4.inc.fixed
@@ -77,11 +77,11 @@ is_textdomain_loaded( 'some-other-plugin' );
  * Incorrect text domain, should be replaced.
  */
 load_textdomain( 'something-else', '/path/to/file.mo' );
-load_plugin_textdomain( 'something-else', false, '/languages/' );
+\load_plugin_textdomain( 'something-else', false, '/languages/' );
 load_muplugin_textdomain( 'something-else', '/languages/' );
 load_theme_textdomain( 'something-else', '/path/to/languages/' );
 load_child_theme_textdomain( 'something-else', '/path/to/languages/' );
-unload_textdomain( 'something-else' );
+unload_TEXTDOMAIN( 'something-else' );
 
 __( $text, 'something-else' );
 _e( $text, 'something-else' );
@@ -287,5 +287,13 @@ __ (
     'something-else'
 );
 
+/*
+ * Safeguard correct handling of namespaced function calls (partially qualified is already tested above).
+ */
+\MyNamespace\load_textdomain( 'text-domain', '/path/to/file.mo' );
+namespace\__( $text, 'text-domain' );
+\ESC_HTML__( $text, 'something-else' );
+\get_translations_for_domain( 'something-else' );
+
 // phpcs:set WordPress.Utils.I18nTextDomainFixer old_text_domain[]
 // phpcs:set WordPress.Utils.I18nTextDomainFixer new_text_domain false
diff --git a/WordPress/Tests/Utils/I18nTextDomainFixerUnitTest.php b/WordPress/Tests/Utils/I18nTextDomainFixerUnitTest.php
index a8c7c95e84..872050aa97 100644
--- a/WordPress/Tests/Utils/I18nTextDomainFixerUnitTest.php
+++ b/WordPress/Tests/Utils/I18nTextDomainFixerUnitTest.php
@@ -154,6 +154,8 @@ public function getErrorList( $testFile = '' ) {
 					245 => 1,
 					277 => 1,
 					278 => 1,
+					289 => 1,
+					290 => 1,
 				);
 
 			default:
diff --git a/WordPress/Tests/WP/CronIntervalUnitTest.inc b/WordPress/Tests/WP/CronIntervalUnitTest.inc
index e9541f49d2..5ebc161d4c 100644
--- a/WordPress/Tests/WP/CronIntervalUnitTest.inc
+++ b/WordPress/Tests/WP/CronIntervalUnitTest.inc
@@ -165,9 +165,9 @@ add_filter( 'cron_schedules', function ( $schedules ) {
 class FQNConstants {
 	public function add_schedules() {
 		add_filter( 'cron_schedules', array( $this, 'add_weekly_schedule' ) ); // Ok: > 15 min.
-		add_filter( 'cron_schedules', array( $this, 'add_eight_minute_schedule' ) ); // Warning: 8 min.
-		add_filter( 'cron_schedules', array( $this, 'add_hundred_minute_schedule' ) ); // Warning: time undetermined.
-		add_filter( 'cron_schedules', array( $this, 'sneaky_fake_wp_constant_schedule' ) ); // Warning: time undetermined.
+		\add_filter( 'cron_schedules', array( $this, 'add_eight_minute_schedule' ) ); // Warning: 8 min.
+		ADD_FILTER( 'cron_schedules', array( $this, 'add_hundred_minute_schedule' ) ); // Warning: time undetermined.
+		\Add_Filter( 'cron_schedules', array( $this, 'sneaky_fake_wp_constant_schedule' ) ); // Warning: time undetermined.
 	}
 
 	public function add_weekly_schedule( $schedules ) {
@@ -316,6 +316,7 @@ function first_class_weekly_schedule( $schedules ) {
 }
 add_filter( 'cron_schedules', 'first_class_weekly_schedule'(...)); // Ok: > 15 min.
 add_filter( 'cron_schedules', first_class_weekly_schedule(...)); // Ok: > 15 min.
+add_filter( 'cron_schedules', namespace\first_class_weekly_schedule(...)); // Ok: > 15 min.
 
 function first_class_six_min_schedule( $schedules ) {
 	$schedules['every_6_mins'] = array(
@@ -326,3 +327,35 @@ function first_class_six_min_schedule( $schedules ) {
 }
 add_filter( 'cron_schedules', first_class_six_min_schedule(...)); // Warning: 6 min.
 add_filter( 'cron_schedules', 'first_class_six_min_schedule'(...)); // Warning: 6 min.
+add_filter( 'cron_schedules', \first_class_six_min_schedule(...)); // Warning: 6 min.
+add_filter( 'cron_schedules', namespace\first_class_six_min_schedule(...)); // Warning: 6 min.
+
+/*
+ * The tests below document the current behavior of the sniff, even though they are false negatives. The sniff treats
+ * the first-class callable examples below as if referencing the global function first_class_six_min_schedule()
+ * and not a namespaced function with the same name.
+ *
+ * Related to: https://github.com/WordPress/WordPress-Coding-Standards/issues/2644.
+ */
+add_filter( 'cron_schedules', MyNamespace\first_class_weekly_schedule(...)); // False negative - Ok: > 15 min, but should be marked `ChangeDetected`.
+add_filter( 'cron_schedules', \MyNamespace\first_class_weekly_schedule(...)); // False negative - Ok: > 15 min, but should be marked `ChangeDetected`.
+add_filter( 'cron_schedules', namespace\Sub\first_class_weekly_schedule(...)); // False negative - Ok: > 15 min, but should be marked `ChangeDetected`.
+
+/*
+ * The tests below document the current behavior of the sniff, even though they are false positives. The sniff treats
+ * the first-class callable examples below as if referencing the global function first_class_six_min_schedule()
+ * and not a namespaced function with the same name. Fixing this incorrect behavior is not trivial.
+ *
+ * Related to: https://github.com/WordPress/WordPress-Coding-Standards/issues/2644.
+ */
+add_filter( 'cron_schedules', MyNamespace\first_class_six_min_schedule(...)); // False positive - `CronSchedulesInterval` warning (6 min), but should be `ChangeDetected`.
+add_filter( 'cron_schedules', \MyNamespace\first_class_six_min_schedule(...)); // False positive - `CronSchedulesInterval` warning (6 min), but should be `ChangeDetected`.
+add_filter( 'cron_schedules', namespace\Sub\first_class_six_min_schedule(...)); // False positive - `CronSchedulesInterval` warning (6 min), but should be `ChangeDetected`.
+
+/*
+ * Safeguard correct handling of all types of namespaced function calls (except FQN global function call which is
+ * handled above).
+ */
+MyNamespace\add_filter( 'cron_schedules', 'unknown_callback' ); // Ok.
+\MyNamespace\add_filter( 'cron_schedules', 'unknown_callback' ); // Ok.
+namespace\add_filter( 'cron_schedules', 'unknown_callback' ); // Ok. The sniff should start flagging this once it can resolve relative namespaces.
diff --git a/WordPress/Tests/WP/CronIntervalUnitTest.php b/WordPress/Tests/WP/CronIntervalUnitTest.php
index 81f02c2768..2417abaf41 100644
--- a/WordPress/Tests/WP/CronIntervalUnitTest.php
+++ b/WordPress/Tests/WP/CronIntervalUnitTest.php
@@ -65,8 +65,13 @@ public function getWarningList() {
 			286 => 1,
 			288 => 1,
 			290 => 1,
-			327 => 1,
 			328 => 1,
+			329 => 1,
+			330 => 1,
+			331 => 1,
+			351 => 1,
+			352 => 1,
+			353 => 1,
 		);
 	}
 }
diff --git a/WordPress/Tests/WP/DiscouragedConstantsUnitTest.inc b/WordPress/Tests/WP/DiscouragedConstantsUnitTest.inc
index ea8ae72524..50302d54fc 100644
--- a/WordPress/Tests/WP/DiscouragedConstantsUnitTest.inc
+++ b/WordPress/Tests/WP/DiscouragedConstantsUnitTest.inc
@@ -80,10 +80,10 @@ enum BACKGROUND_COLOR: string implements Colorful {}
 
 // Safeguard support for PHP 8.0+ named parameters.
 define( case_insensitive: false, value: 'something' ); // OK. Well, not really as missing a required param, but that's not the concern of this sniff.
-define( case_insensitive: false, constant_name: 'STYLESHEETPATH', value: 'something' ); // Bad.
+\DEFINE( case_insensitive: false, constant_name: 'STYLESHEETPATH', value: 'something' ); // Bad.
 
 // Safeguard that comments in the parameters are ignored.
-define(
+Define(
 	// Name.
 	'STYLESHEETPATH',
 	// Value.
@@ -102,3 +102,11 @@ enum ContainsConst {
 }
 
 echo HEADER_TEXTCOLOR::$var; // OK.
+
+/*
+ * Safeguard correct handling of all types of namespaced function calls.
+ */
+\define( 'HEADER_IMAGE', 'something' ); // Bad.
+\MyNamespace\define( 'TEMPLATEPATH', 'something' ); // Ok.
+MyNamespace\define( 'PLUGINDIR', 'something' ); // Ok.
+namespace\define( 'MUPLUGINDIR', 'something' ); // Ok.
diff --git a/WordPress/Tests/WP/DiscouragedConstantsUnitTest.php b/WordPress/Tests/WP/DiscouragedConstantsUnitTest.php
index e27fd838c2..138d0eb4ef 100644
--- a/WordPress/Tests/WP/DiscouragedConstantsUnitTest.php
+++ b/WordPress/Tests/WP/DiscouragedConstantsUnitTest.php
@@ -36,26 +36,27 @@ public function getErrorList() {
 	 */
 	public function getWarningList() {
 		return array(
-			50 => 1,
-			51 => 1,
-			52 => 1,
-			53 => 1,
-			54 => 1,
-			55 => 1,
-			56 => 1,
-			57 => 1,
-			58 => 1,
-			59 => 1,
-			60 => 1,
-			61 => 1,
-			63 => 1,
-			64 => 1,
-			66 => 1,
-			67 => 1,
-			71 => 1,
-			72 => 1,
-			83 => 1,
-			88 => 1,
+			50  => 1,
+			51  => 1,
+			52  => 1,
+			53  => 1,
+			54  => 1,
+			55  => 1,
+			56  => 1,
+			57  => 1,
+			58  => 1,
+			59  => 1,
+			60  => 1,
+			61  => 1,
+			63  => 1,
+			64  => 1,
+			66  => 1,
+			67  => 1,
+			71  => 1,
+			72  => 1,
+			83  => 1,
+			88  => 1,
+			109 => 1,
 		);
 	}
 }