test: add new utils test file

spec/utils.spec.ts

@@ -0,0 +1,77 @@
+import * as logUtils from '../src/utils/log-util';
+import { LogLevel } from '../src/enums';
+import { tagBackportReviewers } from '../src/utils';
+
+const backportPROpenedEvent = require('./fixtures/backport_pull_request.opened.json');
+
+jest.mock('../src/constants', () => ({
+  ...jest.requireActual('../src/constants'),
+  DEFAULT_BACKPORT_REVIEW_TEAM: 'electron/wg-releases',
+}));
+
+describe('utils', () => {
+  describe('tagBackportReviewers()', () => {
+    const octokit = {
+      pulls: {
+        requestReviewers: jest.fn(),
+      },
+      repos: {
+        getCollaboratorPermissionLevel: jest.fn().mockReturnValue(
+          Promise.resolve({
+            data: {
+              permission: 'admin',
+            },
+          }),
+        ),
+      },
+    };
+
+    const context = {
+      octokit,
+      repo: jest.fn((obj) => obj),
+      ...backportPROpenedEvent,
+    };
+
+    beforeEach(() => jest.clearAllMocks());
+
+    it('correctly tags team reviewers when user is undefined', async () => {
+      await tagBackportReviewers({ context, targetPrNumber: 1234 });
+      expect(octokit.pulls.requestReviewers).toHaveBeenCalled();
+      expect(octokit.pulls.requestReviewers).toHaveBeenCalledWith({
+        pull_number: 1234,
+        team_reviewers: ['wg-releases'],
+        reviewers: [],
+      });
+    });
+
+    it('correctly tags team reviewers and reviewers when user is defined', async () => {
+      const user = 'abc';
+      await tagBackportReviewers({ context, targetPrNumber: 1234, user });
+      expect(octokit.pulls.requestReviewers).toHaveBeenCalled();
+      expect(octokit.pulls.requestReviewers).toHaveBeenCalledWith({
+        pull_number: 1234,
+        team_reviewers: ['wg-releases'],
+        reviewers: [user],
+      });
+    });
+
+    it('logs an error if tagBackportReviewers throws an error', async () => {
+      const error = new Error('Request failed');
+      context.octokit.pulls.requestReviewers = jest
+        .fn()
+        .mockRejectedValue(error);
+
+      const logSpy = jest.spyOn(logUtils, 'log');
+      await tagBackportReviewers({ context, targetPrNumber: 1234 });
+
+      expect(octokit.pulls.requestReviewers).toHaveBeenCalled();
+
+      expect(logSpy).toHaveBeenCalledWith(
+        'tagBackportReviewers',
+        LogLevel.ERROR,
+        `Failed to request reviewers for PR #1234`,
+        error,
+      );
+    });
+  });
+});