test: stfcEmailHandler function in a unit test (#1215)

close - [1439](UserOfficeProject/issue-tracker#1439)

Author: YufanKambang

apps/backend/src/eventHandlers/email/stfcEmailHandler.spec.ts

@@ -0,0 +1,129 @@
+import 'reflect-metadata';
+import { faker } from '@faker-js/faker';
+import * as Logger from '@user-office-software/duo-logger';
+import { container } from 'tsyringe';
+
+import { Tokens } from '../../config/Tokens';
+import { ApplicationEvent } from '../../events/applicationEvents';
+import { Event } from '../../events/event.enum';
+import { stfcEmailHandler } from './stfcEmailHandler';
+
+const ORIGINAL_ENV = process.env;
+const spyLogError = jest
+  .spyOn(Logger.logger, 'logError')
+  .mockImplementation(() => {});
+const spyLogInfo = jest
+  .spyOn(Logger.logger, 'logInfo')
+  .mockImplementation(() => {});
+// Mock MailService
+const mockMailService = {
+  sendMail: jest.fn(),
+};
+describe('stfcEmailHandler', () => {
+  beforeAll(() => {
+    container.registerInstance(Tokens.MailService, mockMailService);
+  });
+  afterEach(() => {
+    process.env = ORIGINAL_ENV;
+    jest.clearAllMocks();
+    jest.resetModules();
+  });
+
+  describe('These are the test for the handler function stfcEmailhandler', () => {
+    it('When running Node process does not have env.FBS_EMAIL value', () => {
+      process.env.FBS_EMAIL = '';
+      const mockEvent = {
+        type: Event.CALL_CREATED,
+        call: {},
+        isRejection: false,
+      } as ApplicationEvent;
+
+      stfcEmailHandler(mockEvent);
+
+      expect(process.env.FBS_EMAIL).toBe('');
+      expect(spyLogError).toHaveBeenCalledTimes(1);
+      expect(spyLogError).toHaveBeenCalledWith(
+        'Could not send email(s) on call creation, environmental variable (FBS_EMAIL) not found',
+        {}
+      );
+    });
+
+    it('mailService.sendMail is sucessful', async () => {
+      // When all required settings are valid
+      const inviteEmail = faker.internet.email();
+      process.env.FBS_EMAIL = inviteEmail;
+      const mockEvent = {
+        type: Event.CALL_CREATED,
+        call: {
+          shortCode: 'string',
+          startCall: new Date(2000, 1, 1),
+          endCall: new Date(2000, 1, 2),
+        },
+        isRejection: false,
+      } as ApplicationEvent;
+
+      //create mock instances
+      mockMailService.sendMail.mockResolvedValue({ success: true });
+
+      await stfcEmailHandler(mockEvent);
+
+      expect(process.env.FBS_EMAIL).toBe(inviteEmail);
+      expect(mockMailService.sendMail).toHaveBeenCalledWith({
+        content: { template_id: 'call-created-email' },
+        substitution_data: {
+          shortCode: 'string',
+          startCall: new Date(2000, 1, 1),
+          endCall: new Date(2000, 1, 2),
+        },
+        recipients: [{ address: inviteEmail }],
+      });
+      expect(spyLogInfo).toHaveBeenCalledTimes(1);
+      // this result is derived from the SkipSendMailService.ts, as that is what is mapped in the test environment
+      expect(spyLogInfo).toHaveBeenCalledWith('Emails sent on call creation:', {
+        result: {
+          success: true,
+        },
+        event: mockEvent,
+      });
+    });
+
+    it('mailService.sendMail is not sucessful', async () => {
+      // Then mailService.catch is evoked, logError(x) will be present
+      const inviteEmail = faker.internet.email();
+      process.env.FBS_EMAIL = inviteEmail;
+      const mockEvent = {
+        type: Event.CALL_CREATED,
+        call: {
+          shortCode: 'error',
+        },
+        isRejection: false,
+      } as ApplicationEvent;
+      const forcedError = new Error('SMTP down');
+
+      mockMailService.sendMail.mockRejectedValueOnce(forcedError);
+      container.registerInstance(Tokens.MailService, mockMailService);
+
+      await stfcEmailHandler(mockEvent);
+      // have added this line as the class.method in the handler function is not asynced
+      // and the asserts/expects will check before .then or .catch gets process
+      await new Promise(setImmediate);
+
+      expect(mockMailService.sendMail).toHaveBeenCalledWith({
+        content: { template_id: 'call-created-email' },
+        substitution_data: {
+          shortCode: 'error',
+        },
+        recipients: [{ address: inviteEmail }],
+      });
+      expect(mockMailService.sendMail).toHaveBeenCalled();
+      expect(spyLogError).toHaveBeenCalledTimes(1);
+      expect(spyLogError).toHaveBeenCalledWith(
+        'Could not send email(s) on call creation:',
+        {
+          error: forcedError,
+          event: mockEvent,
+        }
+      );
+    });
+  });
+});