test: resolve function-form next config in browser-stubs test

withPostHogConfig wraps the export as a config function, so the test must
resolve it to the object form before accessing .webpack.

Author: huv1k

tests/integration/e2b-browser-stubs.test.ts

@@ -1,3 +1,5 @@
+import type { NextConfig } from 'next'
+import { PHASE_PRODUCTION_BUILD } from 'next/constants'
 import { describe, expect, it } from 'vitest'
 import nextConfig from '../../next.config'
 
@@ -14,14 +16,26 @@ class MockNormalModuleReplacementPlugin {
   }
 }
 
+// withPostHogConfig wraps the config as a function; resolve it to the object form.
+type NextConfigFn = (
+  phase: string,
+  ctx: { defaultConfig: NextConfig }
+) => Promise<NextConfig>
+
+const resolveNextConfig = () =>
+  (nextConfig as unknown as NextConfigFn)(PHASE_PRODUCTION_BUILD, {
+    defaultConfig: {},
+  })
+
 describe('E2B browser module stubs', () => {
-  it('aliases node built-ins after webpack strips node: scheme requests', () => {
+  it('aliases node built-ins after webpack strips node: scheme requests', async () => {
+    const resolved = await resolveNextConfig()
     const webpackConfig = {
       resolve: { alias: {} as Record<string, string> },
       plugins: [] as MockNormalModuleReplacementPlugin[],
     }
 
-    nextConfig.webpack?.(webpackConfig, {
+    resolved.webpack?.(webpackConfig, {
       isServer: false,
       webpack: {
         NormalModuleReplacementPlugin: MockNormalModuleReplacementPlugin,
@@ -53,13 +67,14 @@ describe('E2B browser module stubs', () => {
     )
   })
 
-  it('does not rewrite server webpack builds', () => {
+  it('does not rewrite server webpack builds', async () => {
+    const resolved = await resolveNextConfig()
     const webpackConfig = {
       resolve: { alias: {} as Record<string, string> },
       plugins: [] as MockNormalModuleReplacementPlugin[],
     }
 
-    nextConfig.webpack?.(webpackConfig, {
+    resolved.webpack?.(webpackConfig, {
       isServer: true,
       webpack: {
         NormalModuleReplacementPlugin: MockNormalModuleReplacementPlugin,