Tests: Fix Karma tests on Node.js 20

Node.js 20 started throwing errors when `writeHead` is called twice on
a response. This might have already been invalid before but it wasn't throwing
on Node.js 18.

Compute the headers object and call `writeHead` once to avoid the issue.

Closes gh-5397

1 files changed, 5 insertions, 9 deletions

diff --git a/test/middleware-mockserver.cjs b/test/middleware-mockserver.cjs
index a7a7a47b9..5fb067627 100644
--- a/test/middleware-mockserver.cjs
+++ b/test/middleware-mockserver.cjs
@@ -80,13 +80,7 @@ const mocks = {
 			headers[ "access-control-allow-origin" ] = "*";
 		}
 
-		if ( resp.set ) {
-			resp.set( headers );
-		} else {
-			for ( const key in headers ) {
-				resp.writeHead( 200, { [ key ]: headers[ key ] } );
-			}
-		}
+		resp.writeHead( 200, headers );
 
 		if ( req.query.callback ) {
 			resp.end( `${ cleanCallback( req.query.callback ) }(${ JSON.stringify( {
@@ -105,12 +99,14 @@ const mocks = {
 		);
 	},
 	json: function( req, resp ) {
+		const headers = {};
 		if ( req.query.header ) {
-			resp.writeHead( 200, { "content-type": "application/json" } );
+			headers[ "content-type" ] = "application/json";
 		}
 		if ( req.query.cors ) {
-			resp.writeHead( 200, { "access-control-allow-origin": "*" } );
+			headers[ "access-control-allow-origin" ] = "*";
 		}
+		resp.writeHead( 200, headers );
 		if ( req.query.array ) {
 			resp.end( JSON.stringify(
 				[ { name: "John", age: 21 }, { name: "Peter", age: 25 } ]