diff --git a/tests/phpunit/includes/abstract-testcase.php b/tests/phpunit/includes/abstract-testcase.php
index 933859571b..59ea4635fd 100644
--- a/tests/phpunit/includes/abstract-testcase.php
+++ b/tests/phpunit/includes/abstract-testcase.php
@@ -564,23 +564,25 @@ abstract class WP_UnitTestCase_Base extends PHPUnit_Adapter_TestCase {
 	}
 
 	/**
-	 * PHPUnit 6+ compatibility shim.
+	 * Redundant PHPUnit 6+ compatibility shim. DO NOT USE!
+	 *
+	 * This method is only left in place for backward compatibility reasons.
+	 *
+	 * @deprecated 5.9.0 Use the PHPUnit native expectException*() methods directly.
 	 *
 	 * @param mixed      $exception
 	 * @param string     $message
 	 * @param int|string $code
 	 */
 	public function setExpectedException( $exception, $message = '', $code = null ) {
-		if ( method_exists( 'PHPUnit_Framework_TestCase', 'setExpectedException' ) ) {
-			parent::setExpectedException( $exception, $message, $code );
-		} else {
-			$this->expectException( $exception );
-			if ( '' !== $message ) {
-				$this->expectExceptionMessage( $message );
-			}
-			if ( null !== $code ) {
-				$this->expectExceptionCode( $code );
-			}
+		$this->expectException( $exception );
+
+		if ( '' !== $message ) {
+			$this->expectExceptionMessage( $message );
+		}
+
+		if ( null !== $code ) {
+			$this->expectExceptionCode( $code );
 		}
 	}