[Scheduler-test] add tests for ScraperScheduler

Author: surenpoghosian

src/__tests__/shceduler.test.ts

@@ -0,0 +1,117 @@
+import cron from 'node-cron';
+import ScraperScheduler from '../Scheduler';
+import Main from '../main';
+
+jest.mock('node-cron', () => ({
+  schedule: jest.fn(),
+}));
+
+jest.mock('../main', () => {
+  return jest.fn().mockImplementation(() => {
+    return { run: jest.fn().mockResolvedValue(undefined) };
+  });
+});
+
+describe('ScraperScheduler', () => {
+  const cronExpression = '*/5 * * * *'; // Every 5 minutes
+  let scheduler: ScraperScheduler;
+
+  beforeEach(() => {
+    scheduler = new ScraperScheduler(cronExpression);
+  });
+
+  afterEach(() => {
+    jest.clearAllMocks();
+  });
+
+  it('should initialize with a given cron expression', () => {
+    expect((scheduler as any).cronExpression).toBe(cronExpression);
+    expect((scheduler as any).task).toBeNull();
+  });
+
+  it('should start the scheduler and set up a cron job', () => {
+    const scheduleMock = cron.schedule as jest.Mock;
+    const consoleLogSpy = jest.spyOn(console, 'log').mockImplementation();
+
+    scheduler.start();
+
+    expect(scheduleMock).toHaveBeenCalledWith(
+      cronExpression,
+      expect.any(Function)
+    );
+    expect(consoleLogSpy).toHaveBeenCalledWith(
+      `Scheduler started with cron expression: ${cronExpression}`
+    );
+
+    scheduleMock.mockRestore();
+    consoleLogSpy.mockRestore();
+  });
+
+  it('should call the scrape method when the cron job is triggered', async () => {
+    const scheduleMock = cron.schedule as jest.Mock;
+    const scrapeSpy = jest.spyOn(scheduler, 'scrape').mockResolvedValue(undefined);
+    
+    // Mock the cron.schedule to directly call the provided function
+    scheduleMock.mockImplementation((_, callback) => {
+      callback();
+      return { stop: jest.fn() };
+    });
+
+    await scheduler.start(); // Ensure `start` is awaited for asynchronous handling
+
+    expect(scrapeSpy).toHaveBeenCalled();
+
+    scheduleMock.mockRestore();
+    scrapeSpy.mockRestore();
+  });
+
+  it('should stop the scheduled cron job', () => {
+    const stopMock = jest.fn();
+    (scheduler as any).task = { stop: stopMock };
+
+    const consoleLogSpy = jest.spyOn(console, 'log').mockImplementation();
+
+    scheduler.stop();
+
+    expect(stopMock).toHaveBeenCalled();
+    expect(consoleLogSpy).toHaveBeenCalledWith('Scheduler stopped.');
+
+    stopMock.mockRestore();
+    consoleLogSpy.mockRestore();
+  });
+
+  it('should do nothing if stop is called when no task is scheduled', () => {
+    const stopMock = jest.fn();
+
+    const consoleLogSpy = jest.spyOn(console, 'log').mockImplementation();
+
+    scheduler.stop();
+
+    expect(stopMock).not.toHaveBeenCalled();
+    expect(consoleLogSpy).not.toHaveBeenCalled();
+
+    consoleLogSpy.mockRestore();
+  });
+
+  it('should handle errors in the scrape method gracefully', async () => {
+    const scheduleMock = cron.schedule as jest.Mock;
+    const error = new Error('Scraping error');
+    const scrapeSpy = jest.spyOn(scheduler, 'scrape').mockRejectedValue(error);
+    const consoleErrorSpy = jest.spyOn(console, 'error').mockImplementation();
+
+    scheduleMock.mockImplementation((_, callback) => {
+      callback();
+      return { stop: jest.fn() };
+    });
+
+    await scheduler.start(); // Ensure `start` is awaited for asynchronous handling
+
+    await new Promise((resolve) => setImmediate(resolve)); // Allow time for async operations
+
+    expect(consoleErrorSpy).toHaveBeenCalledWith('Error during scraping:', error);
+
+    scheduleMock.mockRestore();
+    scrapeSpy.mockRestore();
+    consoleErrorSpy.mockRestore();
+  });
+});