Refactor environment variable handling for Vitest integration

code/addons/a11y/src/utils.ts

@@ -1,25 +1,17 @@
 export function getIsVitestStandaloneRun() {
   try {
-    return process.env.VITEST_STORYBOOK === 'false';
-  } catch {
-    try {
-      // @ts-expect-error Suppress TypeScript warning about wrong setting. Doesn't matter, because we don't use tsc for bundling.
-      return import.meta.env.VITEST_STORYBOOK === 'false';
-    } catch (e) {
-      return false;
-    }
+    // @ts-expect-error Suppress TypeScript warning about wrong setting. Doesn't matter, because we don't use tsc for bundling.
+    return import.meta.env.VITEST_STORYBOOK === 'false';
+  } catch (e) {
+    return false;
   }
 }
 
 export function getIsVitestRunning() {
   try {
-    return process?.env.MODE === 'test';
-  } catch {
-    try {
-      // @ts-expect-error Suppress TypeScript warning about wrong setting. Doesn't matter, because we don't use tsc for bundling.
-      return import.meta.env.MODE === 'test';
-    } catch (e) {
-      return false;
-    }
+    // @ts-expect-error Suppress TypeScript warning about wrong setting. Doesn't matter, because we don't use tsc for bundling.
+    return import.meta.env.MODE === 'test';
+  } catch (e) {
+    return false;
   }
 }

code/addons/test/src/vitest-plugin/index.ts

@@ -23,7 +23,6 @@ import sirv from 'sirv';
 import { convertPathToPattern } from 'tinyglobby';
 import { dedent } from 'ts-dedent';
 
-import { TestManager } from '../node/test-manager';
 import type { InternalOptions, UserOptions } from './types';
 
 const WORKING_DIR = process.cwd();
@@ -143,6 +142,10 @@ export const storybookTest = async (options?: UserOptions): Promise<Plugin> => {
       //   plugin.name?.startsWith('vitest:browser')
       // )
 
+      // We signal the test runner that we are not running it via Storybook
+      // We are overriding the environment variable to 'true' if vitest runs via @storybook/addon-test's backend
+      const vitestStorybook = process.env.VITEST_STORYBOOK ?? 'false';
+
       const baseConfig: Omit<ViteUserConfig, 'plugins'> = {
         test: {
           setupFiles: [
@@ -162,9 +165,8 @@ export const storybookTest = async (options?: UserOptions): Promise<Plugin> => {
             ...storybookEnv,
             // To be accessed by the setup file
             __STORYBOOK_URL__: finalOptions.storybookUrl,
-            // We signal the test runner that we are not running it via Storybook
-            // We are overriding the environment variable to 'true' if vitest runs via @storybook/addon-test's backend
-            VITEST_STORYBOOK: 'false',
+
+            VITEST_STORYBOOK: vitestStorybook,
             __VITEST_INCLUDE_TAGS__: finalOptions.tags.include.join(','),
             __VITEST_EXCLUDE_TAGS__: finalOptions.tags.exclude.join(','),
             __VITEST_SKIP_TAGS__: finalOptions.tags.skip.join(','),
@@ -239,8 +241,6 @@ export const storybookTest = async (options?: UserOptions): Promise<Plugin> => {
         },
 
         define: {
-          // polyfilling process.env.VITEST_STORYBOOK to 'false' in the browser
-          'process.env.VITEST_STORYBOOK': JSON.stringify('false'),
           ...(frameworkName?.includes('vue3')
             ? { __VUE_PROD_HYDRATION_MISMATCH_DETAILS__: 'false' }
             : {}),