try using helper function in one test

Author: lobsterkatie

packages/nextjs/test/config.test.ts

@@ -15,6 +15,7 @@ import {
 } from '../src/config/types';
 import {
   constructWebpackConfigFunction,
+  findWebpackPlugin,
   getUserConfigFile,
   getWebpackPluginOptions,
   SentryWebpackPlugin,
@@ -335,8 +336,12 @@ describe('Sentry webpack plugin config', () => {
       incomingWebpackConfig: serverWebpackConfig,
       incomingWebpackBuildContext: serverBuildContext,
     });
+    const sentryWebpackPluginInstance = findWebpackPlugin(
+      finalWebpackConfig,
+      'SentryCliPlugin',
+    ) as SentryWebpackPluginType;
 
-    expect(finalWebpackConfig.plugins?.[0].options).toEqual(
+    expect(sentryWebpackPluginInstance.options).toEqual(
       expect.objectContaining({
         include: expect.any(Array), // default, tested separately elsewhere
         ignore: [], // default