diff --git a/packages/steiger-plugin-fsd/src/_lib/prepare-test.ts b/packages/steiger-plugin-fsd/src/_lib/prepare-test.ts
index f7a5ea2..7daf1b4 100644
--- a/packages/steiger-plugin-fsd/src/_lib/prepare-test.ts
+++ b/packages/steiger-plugin-fsd/src/_lib/prepare-test.ts
@@ -1,6 +1,8 @@
-import { join } from 'node:path'
+import { join, sep } from 'node:path'
+import type { readFileSync, existsSync } from 'node:fs'
 import type { Folder, File, FsdRoot } from '@feature-sliced/filesystem'
 import type { Diagnostic } from '../types.js'
+import { vi } from 'vitest'
 
 /** Parse a multi-line indented string with emojis for files and folders into an FSD root. */
 export function parseIntoFsdRoot(fsMarkup: string): FsdRoot {
@@ -42,6 +44,27 @@ export function joinFromRoot(...segments: Array<string>) {
   return join('/', ...segments)
 }
 
+export function createFsMocks(mockedFiles: Record<string, string>, original: typeof import('fs')) {
+  const normalizedMockedFiles = Object.fromEntries(
+    Object.entries(mockedFiles).map(([path, content]) => [path.replace(/\//g, sep), content]),
+  )
+
+  return {
+    ...original,
+    readFileSync: vi.fn(((path, options) => {
+      if (typeof path === 'string' && path in normalizedMockedFiles) {
+        return normalizedMockedFiles[path as keyof typeof normalizedMockedFiles]
+      } else {
+        return original.readFileSync(path, options)
+      }
+    }) as typeof readFileSync),
+    existsSync: vi.fn(((path) =>
+      Object.keys(normalizedMockedFiles).some(
+        (key) => key === path || key.startsWith(path + sep),
+      )) as typeof existsSync),
+  }
+}
+
 if (import.meta.vitest) {
   const { test, expect } = import.meta.vitest
 
diff --git a/packages/steiger-plugin-fsd/src/forbidden-imports/index.spec.ts b/packages/steiger-plugin-fsd/src/forbidden-imports/index.spec.ts
index 9a336d0..01264e9 100644
--- a/packages/steiger-plugin-fsd/src/forbidden-imports/index.spec.ts
+++ b/packages/steiger-plugin-fsd/src/forbidden-imports/index.spec.ts
@@ -1,6 +1,4 @@
 import { expect, it, vi } from 'vitest'
-import type { readFileSync } from 'node:fs'
-import { sep } from 'node:path'
 
 import { parseIntoFsdRoot } from '../_lib/prepare-test.js'
 import forbiddenImports from './index.js'
@@ -13,36 +11,28 @@ vi.mock('tsconfck', async (importOriginal) => {
 })
 
 vi.mock('node:fs', async (importOriginal) => {
-  const original = await importOriginal<typeof import('fs')>()
+  const originalFs = await importOriginal<typeof import('fs')>()
+  const { createFsMocks } = await import('../_lib/prepare-test.js')
 
-  const mockedFiles = {
-    '/shared/ui/styles.ts': '',
-    '/shared/ui/Button.tsx': 'import styles from "./styles";',
-    '/shared/ui/TextField.tsx': 'import styles from "./styles";',
-    '/shared/ui/index.ts': '',
-    '/entities/user/ui/UserAvatar.tsx': 'import { Button } from "@/shared/ui"',
-    '/entities/user/index.ts': '',
-    '/entities/product/ui/ProductCard.tsx': 'import { UserAvatar } from "@/entities/user"',
-    '/entities/product/index.ts': '',
-    '/features/comments/ui/CommentCard.tsx': 'import { styles } from "@/pages/editor"',
-    '/features/comments/index.ts': '',
-    '/pages/editor/ui/styles.ts': '',
-    '/pages/editor/ui/EditorPage.tsx': 'import { Button } from "@/shared/ui"; import { Editor } from "./Editor"',
-    '/pages/editor/ui/Editor.tsx': 'import { TextField } from "@/shared/ui"',
-    '/pages/editor/index.ts': '',
-  }
-
-  return {
-    ...original,
-    readFileSync: vi.fn(((path, options) => {
-      if (typeof path === 'string' && path in mockedFiles) {
-        return mockedFiles[path as keyof typeof mockedFiles]
-      } else {
-        return original.readFileSync(path, options)
-      }
-    }) as typeof readFileSync),
-    existsSync: vi.fn((path) => Object.keys(mockedFiles).some((key) => key === path || key.startsWith(path + sep))),
-  }
+  return createFsMocks(
+    {
+      '/shared/ui/styles.ts': '',
+      '/shared/ui/Button.tsx': 'import styles from "./styles";',
+      '/shared/ui/TextField.tsx': 'import styles from "./styles";',
+      '/shared/ui/index.ts': '',
+      '/entities/user/ui/UserAvatar.tsx': 'import { Button } from "@/shared/ui"',
+      '/entities/user/index.ts': '',
+      '/entities/product/ui/ProductCard.tsx': 'import { UserAvatar } from "@/entities/user"',
+      '/entities/product/index.ts': '',
+      '/features/comments/ui/CommentCard.tsx': 'import { styles } from "@/pages/editor"',
+      '/features/comments/index.ts': '',
+      '/pages/editor/ui/styles.ts': '',
+      '/pages/editor/ui/EditorPage.tsx': 'import { Button } from "@/shared/ui"; import { Editor } from "./Editor"',
+      '/pages/editor/ui/Editor.tsx': 'import { TextField } from "@/shared/ui"',
+      '/pages/editor/index.ts': '',
+    },
+    originalFs,
+  )
 })
 
 it('reports no errors on a project with only correct imports', async () => {
diff --git a/packages/steiger-plugin-fsd/src/insignificant-slice/index.spec.ts b/packages/steiger-plugin-fsd/src/insignificant-slice/index.spec.ts
index 9888ac5..d00a8e1 100644
--- a/packages/steiger-plugin-fsd/src/insignificant-slice/index.spec.ts
+++ b/packages/steiger-plugin-fsd/src/insignificant-slice/index.spec.ts
@@ -1,6 +1,4 @@
 import { expect, it, vi } from 'vitest'
-import type { readFileSync } from 'node:fs'
-import { sep } from 'node:path'
 
 import { compareMessages, parseIntoFsdRoot } from '../_lib/prepare-test.js'
 import insignificantSlice from './index.js'
@@ -13,40 +11,32 @@ vi.mock('tsconfck', async (importOriginal) => {
 })
 
 vi.mock('node:fs', async (importOriginal) => {
-  const original = await importOriginal<typeof import('fs')>()
+  const originalFs = await importOriginal<typeof import('fs')>()
+  const { createFsMocks } = await import('../_lib/prepare-test.js')
 
-  const mockedFiles = {
-    '/shared/ui/styles.ts': '',
-    '/shared/ui/Button.tsx': 'import styles from "./styles";',
-    '/shared/ui/TextField.tsx': 'import styles from "./styles";',
-    '/shared/ui/index.ts': '',
-    '/entities/user/ui/UserAvatar.tsx': 'import { Button } from "@/shared/ui"',
-    '/entities/user/index.ts': '',
-    '/entities/product/ui/ProductCard.tsx': '',
-    '/entities/product/index.ts': '',
-    '/features/comments/ui/CommentCard.tsx': '',
-    '/features/comments/index.ts': '',
-    '/pages/editor/ui/EditorPage.tsx':
-      'import { Button } from "@/shared/ui"; import { Editor } from "./Editor"; import { CommentCard } from "@/features/comments"; import { UserAvatar } from "@/entities/user"',
-    '/pages/editor/ui/Editor.tsx':
-      'import { TextField } from "@/shared/ui"; import { UserAvatar } from "@/entities/user"',
-    '/pages/editor/index.ts': '',
-    '/pages/settings/ui/SettingsPage.tsx':
-      'import { Button } from "@/shared/ui"; import { CommentCard } from "@/features/comments"',
-    '/pages/settings/index.ts': '',
-  }
-
-  return {
-    ...original,
-    readFileSync: vi.fn(((path, options) => {
-      if (typeof path === 'string' && path in mockedFiles) {
-        return mockedFiles[path as keyof typeof mockedFiles]
-      } else {
-        return original.readFileSync(path, options)
-      }
-    }) as typeof readFileSync),
-    existsSync: vi.fn((path) => Object.keys(mockedFiles).some((key) => key === path || key.startsWith(path + sep))),
-  }
+  return createFsMocks(
+    {
+      '/shared/ui/styles.ts': '',
+      '/shared/ui/Button.tsx': 'import styles from "./styles";',
+      '/shared/ui/TextField.tsx': 'import styles from "./styles";',
+      '/shared/ui/index.ts': '',
+      '/entities/user/ui/UserAvatar.tsx': 'import { Button } from "@/shared/ui"',
+      '/entities/user/index.ts': '',
+      '/entities/product/ui/ProductCard.tsx': '',
+      '/entities/product/index.ts': '',
+      '/features/comments/ui/CommentCard.tsx': '',
+      '/features/comments/index.ts': '',
+      '/pages/editor/ui/EditorPage.tsx':
+        'import { Button } from "@/shared/ui"; import { Editor } from "./Editor"; import { CommentCard } from "@/features/comments"; import { UserAvatar } from "@/entities/user"',
+      '/pages/editor/ui/Editor.tsx':
+        'import { TextField } from "@/shared/ui"; import { UserAvatar } from "@/entities/user"',
+      '/pages/editor/index.ts': '',
+      '/pages/settings/ui/SettingsPage.tsx':
+        'import { Button } from "@/shared/ui"; import { CommentCard } from "@/features/comments"',
+      '/pages/settings/index.ts': '',
+    },
+    originalFs,
+  )
 })
 
 it('reports no errors on a project with slices only on the Pages layer', async () => {
diff --git a/packages/steiger-plugin-fsd/src/no-public-api-sidestep/index.spec.ts b/packages/steiger-plugin-fsd/src/no-public-api-sidestep/index.spec.ts
index 8ef1f88..e18dfd6 100644
--- a/packages/steiger-plugin-fsd/src/no-public-api-sidestep/index.spec.ts
+++ b/packages/steiger-plugin-fsd/src/no-public-api-sidestep/index.spec.ts
@@ -1,6 +1,4 @@
 import { expect, it, vi } from 'vitest'
-import type { readFileSync } from 'node:fs'
-import { sep } from 'node:path'
 
 import { parseIntoFsdRoot } from '../_lib/prepare-test.js'
 import noPublicApiSidestep from './index.js'
@@ -13,38 +11,30 @@ vi.mock('tsconfck', async (importOriginal) => {
 })
 
 vi.mock('node:fs', async (importOriginal) => {
-  const original = await importOriginal<typeof import('fs')>()
+  const originalFs = await importOriginal<typeof import('fs')>()
+  const { createFsMocks } = await import('../_lib/prepare-test.js')
 
-  const mockedFiles = {
-    '/shared/ui/styles.ts': '',
-    '/shared/ui/Button.tsx': 'import styles from "./styles";',
-    '/shared/ui/TextField.tsx': 'import styles from "./styles";',
-    '/shared/ui/index.ts': '',
-    '/entities/user/ui/UserAvatar.tsx': 'import { Button } from "@/shared/ui"',
-    '/entities/user/index.ts': '',
-    '/entities/product/ui/ProductCard.tsx': 'import { UserAvatar } from "@/entities/user"',
-    '/entities/product/index.ts': '',
-    '/features/comments/ui/CommentCard.tsx': 'import { styles } from "@/pages/editor"',
-    '/features/comments/index.ts': '',
-    '/pages/editor/ui/styles.ts': '',
-    '/pages/editor/ui/EditorPage.tsx': 'import { Button } from "@/shared/ui"; import { Editor } from "./Editor"',
-    '/pages/editor/ui/Editor.tsx':
-      'import { TextField } from "@/shared/ui"; import { ProductCard } from "@/entities/product/ui/ProductCard.tsx"',
-    '/pages/editor/ui/SubmitButton.tsx': 'import { Button } from "@/shared/ui/Button"',
-    '/pages/editor/index.ts': '',
-  }
-
-  return {
-    ...original,
-    readFileSync: vi.fn(((path, options) => {
-      if (typeof path === 'string' && path in mockedFiles) {
-        return mockedFiles[path as keyof typeof mockedFiles]
-      } else {
-        return original.readFileSync(path, options)
-      }
-    }) as typeof readFileSync),
-    existsSync: vi.fn((path) => Object.keys(mockedFiles).some((key) => key === path || key.startsWith(path + sep))),
-  }
+  return createFsMocks(
+    {
+      '/shared/ui/styles.ts': '',
+      '/shared/ui/Button.tsx': 'import styles from "./styles";',
+      '/shared/ui/TextField.tsx': 'import styles from "./styles";',
+      '/shared/ui/index.ts': '',
+      '/entities/user/ui/UserAvatar.tsx': 'import { Button } from "@/shared/ui"',
+      '/entities/user/index.ts': '',
+      '/entities/product/ui/ProductCard.tsx': 'import { UserAvatar } from "@/entities/user"',
+      '/entities/product/index.ts': '',
+      '/features/comments/ui/CommentCard.tsx': 'import { styles } from "@/pages/editor"',
+      '/features/comments/index.ts': '',
+      '/pages/editor/ui/styles.ts': '',
+      '/pages/editor/ui/EditorPage.tsx': 'import { Button } from "@/shared/ui"; import { Editor } from "./Editor"',
+      '/pages/editor/ui/Editor.tsx':
+        'import { TextField } from "@/shared/ui"; import { ProductCard } from "@/entities/product/ui/ProductCard.tsx"',
+      '/pages/editor/ui/SubmitButton.tsx': 'import { Button } from "@/shared/ui/Button"',
+      '/pages/editor/index.ts': '',
+    },
+    originalFs,
+  )
 })
 
 it('reports no errors on a project without public API sidesteps', async () => {