test: restore chunk splitting in middleware for Edge Runtime case

Author: pieh

tests/fixtures/middleware/next.config.js

@@ -11,8 +11,11 @@ const nextConfig = {
   webpack: (config) => {
     // this is a trigger to generate multiple `.next/server/middleware-[hash].js` files instead of
     // single `.next/server/middleware.js` file
-    // this doesn't seem to actually work with Node Middleware - it result in next build failures
-    // config.optimization.splitChunks.maxSize = 100_000
+    if (process.env.SPLIT_CHUNKS) {
+      // this doesn't seem to actually work with Node Middleware - it result in next build failures
+      // so we only do this for default/Edge Runtime
+      config.optimization.splitChunks.maxSize = 100_000
+    }
 
     return config
   },

tests/fixtures/middleware/test-variants.json

@@ -1,4 +1,9 @@
 {
+  "default": {
+    "env": {
+      "SPLIT_CHUNKS": "true"
+    }
+  },
   "node-middleware": {
     "distDir": ".next-node-middleware",
     "files": {