scaffolder-backend: refactor NunjucksWorkflowRunner tests to avoid mock-fs

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

plugins/scaffolder-backend/src/scaffolder/tasks/NunjucksWorkflowRunner.test.ts

@@ -14,10 +14,7 @@
  * limitations under the License.
  */
 
-import mockFs from 'mock-fs';
-import * as winston from 'winston';
-
-import { getVoidLogger, resolvePackagePath } from '@backstage/backend-common';
+import { getVoidLogger } from '@backstage/backend-common';
 import { NunjucksWorkflowRunner } from './NunjucksWorkflowRunner';
 import { TemplateActionRegistry } from '../actions';
 import { ScmIntegrations } from '@backstage/integration';
@@ -36,19 +33,7 @@ import {
   PermissionEvaluator,
 } from '@backstage/plugin-permission-common';
 import { RESOURCE_TYPE_SCAFFOLDER_ACTION } from '@backstage/plugin-scaffolder-common/alpha';
-
-// The Stream module is lazy loaded, so make sure it's in the module cache before mocking fs
-void winston.transports.Stream;
-
-const realFiles = Object.fromEntries(
-  [
-    resolvePackagePath(
-      '@backstage/plugin-scaffolder-backend',
-      'assets',
-      'nunjucks.js.txt',
-    ),
-  ].map(k => [k, mockFs.load(k)]),
-);
+import { createMockDirectory } from '@backstage/backend-test-utils';
 
 describe('DefaultWorkflowRunner', () => {
   const logger = getVoidLogger();
@@ -56,6 +41,8 @@ describe('DefaultWorkflowRunner', () => {
   let runner: NunjucksWorkflowRunner;
   let fakeActionHandler: jest.Mock;
 
+  const mockDir = createMockDirectory();
+
   const mockedPermissionApi: jest.Mocked<PermissionEvaluator> = {
     authorizeConditional: jest.fn(),
   } as unknown as jest.Mocked<PermissionEvaluator>;
@@ -84,11 +71,7 @@ describe('DefaultWorkflowRunner', () => {
   });
 
   beforeEach(() => {
-    winston.format.simple(); // put logform in the require.cache before mocking fs
-    mockFs({
-      '/tmp': mockFs.directory(),
-      ...realFiles,
-    });
+    mockDir.clear();
 
     jest.resetAllMocks();
     actionRegistry = new TemplateActionRegistry();
@@ -148,16 +131,12 @@ describe('DefaultWorkflowRunner', () => {
     runner = new NunjucksWorkflowRunner({
       actionRegistry,
       integrations,
-      workingDirectory: '/tmp',
+      workingDirectory: mockDir.path,
       logger,
       permissions: mockedPermissionApi,
     });
   });
 
-  afterEach(() => {
-    mockFs.restore();
-  });
-
   it('should throw an error if the action does not exist', async () => {
     const task = createMockTaskWithSpec({
       apiVersion: 'scaffolder.backstage.io/v1beta3',