tests: add

Author: anshumanv

test/middleware.test.js

@@ -2439,7 +2439,9 @@ describe.each([
           const compiler = getCompiler(webpackConfig);
 
           instance = middleware(compiler, {
-            headers: () => ({ 'X-nonsense-1': 'yes', 'X-nonsense-2': 'no' }),
+            headers: () => {
+              return { 'X-nonsense-1': 'yes', 'X-nonsense-2': 'no' };
+            },
           });
 
           app = framework();
@@ -2481,6 +2483,7 @@ describe.each([
           const compiler = getCompiler(webpackConfig);
 
           instance = middleware(compiler, {
+            // eslint-disable-next-line no-unused-vars
             headers: (req, res, context) => {
               res.setHeader('X-nonsense-1', 'yes');
               res.setHeader('X-nonsense-2', 'no');