tests: return a string from the mocked Parser::recursiveTagParse

MediaWiki master declares Parser::recursiveTagParse() and
recursiveTagParseFully() with a `string` return type. The component test
mocks stub them with returnArgument(0), echoing the input verbatim. When a
component passes a non-string attribute value (a bool or int) to the parser,
the mock returns that non-string and PHPUnit's typed mock throws "Return
value must be of type string".

Cast the echoed value to string so the mocks honour the method's contract.
Behaviour is unchanged for string inputs, and the renderErrorMessage mock is
left as-is.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: malberts

tests/phpunit/Unit/CarouselGalleryTest.php

@@ -52,7 +52,9 @@ public function testToHtml( $imageList, $additionalAttributes, $expectedOutput )
 			->getMock();
 		$instance->mParser->expects( $this->any() )
 			->method( 'recursiveTagParse' )
-			->will( $this->returnArgument( 0 ) );
+			->will( $this->returnCallback( function ( $text ) {
+				return (string)$text;
+			} ) );
 
 		foreach ( $imageList as $imageData ) {
 			$instance->add( Title::newFromText( $imageData[0] ), $imageData[1], $imageData[2], $imageData[3], $imageData[4] );

tests/phpunit/Unit/ComponentsTestBase.php

@@ -58,10 +58,14 @@ public function setUp(): void {
 		$this->parser = $this->createMock( Parser::class );
 		$this->parser->expects( $this->any() )
 			->method( 'recursiveTagParse' )
-			->will( $this->returnArgument( 0 ) );
+			->will( $this->returnCallback( function ( $text ) {
+				return (string)$text;
+			} ) );
 		$this->parser->expects( $this->any() )
 			->method( 'recursiveTagParseFully' )
-			->will( $this->returnArgument( 0 ) );
+			->will( $this->returnCallback( function ( $text ) {
+				return (string)$text;
+			} ) );
 		$this->parserOutputHelper = $this->createMock( ParserOutputHelper::class );
 		$this->parserOutputHelper->expects( $this->any() )
 			->method( 'renderErrorMessage' )