diff --git a/tests/html-integrity-v1774.mjs b/tests/html-integrity-v1774.mjs
new file mode 100644
index 0000000..9342b58
--- /dev/null
+++ b/tests/html-integrity-v1774.mjs
@@ -0,0 +1,11 @@
+import fs from 'node:fs';
+const html=fs.readFileSync('public/index.html','utf8');
+let bad=0;
+const check=(value,message)=>{console.log(`${value?'OK':'FAIL'}: ${message}`);if(!value)bad++};
+const opens=(html.match(/<style(?:\s|>)/gi)||[]).length;
+const closes=(html.match(/<\/style>/gi)||[]).length;
+check(opens===closes,`style tags balanced (${opens} open / ${closes} close)`);
+check(!html.includes('}<style id="sun-composition-v1757">'),'mobile style is not nested into composition style');
+check(html.includes('}</style><style id="sun-composition-v1757">'),'mobile style closes before composition style');
+check(/<\/style>\s*<\/head>/i.test(html),'last head style is closed before </head>');
+if(bad)process.exit(1);