chore: replace mock-fs with memfs that works in node20

.projenrc.ts

@@ -98,11 +98,11 @@ const project = new typescript.TypeScriptProject({
     '@actions/core',
     '@actions/github',
     '@types/commonmark',
-    '@types/mock-fs',
     '@types/stream-json',
     '@types/tar',
     '@types/workerpool',
-    'mock-fs',
+    'fs-monkey',
+    'memfs',
     'tar',
     'ts-node',
   ],

test/jsii/assemblies.test.ts

@@ -1,12 +1,14 @@
 import { promises as fs } from 'node:fs';
 import * as path from 'node:path';
 import * as spec from '@jsii/spec';
-import * as mockfs from 'mock-fs';
+import { Volume } from 'memfs';
 
 import { fakeAssembly } from './fake-assembly';
 import { allTypeScriptSnippets } from '../../lib/jsii/assemblies';
 import { SnippetParameters } from '../../lib/snippet';
 import { TestJsiiModule, DUMMY_JSII_CONFIG } from '../testutil';
+// eslint-disable-next-line @typescript-eslint/no-require-imports
+const { patchFs } = require('fs-monkey');
 
 jest.setTimeout(30_000);
 
@@ -201,9 +203,11 @@ test('Fixture allows use of import statements', async () => {
 });
 
 test('Backwards compatibility with literate integ tests', async () => {
-  mockfs({
-    '/package/test/integ.example.lit.ts': '# Some literate source file',
-  });
+  const unpatch = patchFs(
+    Volume.fromJSON({
+      '/package/test/integ.example.lit.ts': '# Some literate source file',
+    }),
+  );
 
   try {
     const snippets = Array.from(
@@ -231,7 +235,7 @@ test('Backwards compatibility with literate integ tests', async () => {
       path.normalize('/package/test'),
     );
   } finally {
-    mockfs.restore();
+    unpatch();
   }
 });
 

test/rosetta.test.ts

@@ -1,5 +1,4 @@
-import * as mockfs from 'mock-fs';
-
+import { Volume } from 'memfs';
 import { fakeAssembly } from './jsii/fake-assembly';
 import { testSnippetLocation } from './testutil';
 import {
@@ -12,6 +11,8 @@ import {
   UnknownSnippetMode,
 } from '../lib';
 import { TargetLanguage } from '../lib/languages';
+// eslint-disable-next-line @typescript-eslint/no-require-imports
+const { patchFs } = require('fs-monkey');
 
 const SAMPLE_CODE: TypeScriptSnippet = {
   visibleSource: 'callThisFunction();',
@@ -218,11 +219,13 @@ describe('Rosetta object with disclaimers', () => {
 });
 
 describe('with mocked filesystem', () => {
-  beforeEach(() => {
-    mockfs();
-  });
+  const vol = Volume.fromJSON({});
+  const unpatchFs = patchFs(vol);
   afterEach(() => {
-    mockfs.restore();
+    vol.reset();
+  });
+  afterAll(() => {
+    unpatchFs();
   });
 
   const tablet = new LanguageTablet();