Parallelism in Playwright: Can We Run Some Test Cases Parallelly and Others Sequentially?

As we dive deeper into the world of automation testing, we’re constantly seeking ways to optimize our test suites for speed and efficiency. One approach is to run tests in parallel, which can significantly reduce the overall execution time. But what if we want to run only some of our test cases in parallel, while others need to be executed sequentially? Is it feasible to achieve this hybrid approach in Playwright? In this article, we’ll explore the possibilities and provide a step-by-step guide on how to implement parallel and sequential testing in Playwright.

Why Do We Need to Run Some Tests in Parallel and Others Sequentially?

There are several scenarios where running some tests in parallel and others sequentially makes sense:

• Independent tests**: When you have tests that are completely independent of each other, running them in parallel can significantly reduce the overall execution time.
• Interdependent tests**: However, when tests are interdependent, running them sequentially ensures that the tests are executed in the correct order, and the results are accurate.
• Resource-intensive tests**: Tests that require extensive resources, such as CPU or memory, may need to be run sequentially to avoid overloading the system.
• CI/CD pipeline optimization**: By running some tests in parallel and others sequentially, you can optimize your CI/CD pipeline to minimize execution time and maximize resource allocation.

Understanding Playwright’s Parallelism Capabilities

Playwright, a popular browser automation framework, provides built-in support for parallel testing. You can run multiple browser contexts in parallel using the `browserType.launch()` method, which allows you to create multiple instances of the browser.

const playwright = require('playwright');

(async () => {
  const browser = await playwright.chromium.launch();
  const context1 = await browser.newContext();
  const context2 = await browser.newContext();

  // Run tests in parallel using context1 and context2
})();

However, Playwright’s parallelism capabilities are not limited to just browser contexts. You can also run multiple tests in parallel using the `test.describe.parallel()` method.

const playwright = require('playwright');

(async () => {
  const browser = await playwright.chromium.launch();
  const context = await browser.newContext();

  test.describe.parallel('Parallel tests', () => {
    test('Test 1', async () => {
      // Test 1 code
    });

    test('Test 2', async () => {
      // Test 2 code
    });

    test('Test 3', async () => {
      // Test 3 code
    });
  });
})();

Implementing Hybrid Parallel and Sequential Testing in Playwright

Now that we’ve explored Playwright’s parallelism capabilities, let’s dive into implementing a hybrid approach that allows us to run some tests in parallel and others sequentially.

Step 1: Identify Independent and Interdependent Tests

Begin by identifying the tests that can be run in parallel and those that need to be executed sequentially. Create two separate lists or arrays to store the test names or descriptions.

const parallelTests = [
  'Test 1',
  'Test 2',
  'Test 3',
];

const sequentialTests = [
  'Test 4',
  'Test 5',
  'Test 6',
];

Step 2: Create a Parallel Test Suite

Create a new test suite using the `test.describe.parallel()` method and add the parallel tests to it.

test.describe.parallel('Parallel tests', () => {
  parallelTests.forEach((testName) => {
    test(testName, async () => {
      // Code for each parallel test
    });
  });
});

Step 3: Create a Sequential Test Suite

Create a new test suite using the `test.describe()` method and add the sequential tests to it.

test.describe('Sequential tests', () => {
  sequentialTests.forEach((testName) => {
    test(testName, async () => {
      // Code for each sequential test
    });
  });
});

Step 4: Run the Hybrid Test Suite

Finally, run the hybrid test suite, which includes both parallel and sequential tests. You can use a test runner like Jest or Mocha to execute the tests.

npx jest

Example Code: Hybrid Parallel and Sequential Testing in Playwright

Here’s an example code snippet that demonstrates the hybrid approach:

const playwright = require('playwright');

(async () => {
  const browser = await playwright.chromium.launch();
  const context = await browser.newContext();

  const parallelTests = [
    'Test 1',
    'Test 2',
    'Test 3',
  ];

  const sequentialTests = [
    'Test 4',
    'Test 5',
    'Test 6',
  ];

  test.describe.parallel('Parallel tests', () => {
    parallelTests.forEach((testName) => {
      test(testName, async () => {
        // Code for each parallel test
        await context.newPage();
        await page.goto('https://example.com');
        await page.click('button');
      });
    });
  });

  test.describe('Sequential tests', () => {
    sequentialTests.forEach((testName) => {
      test(testName, async () => {
        // Code for each sequential test
        await context.newPage();
        await page.goto('https://example.com');
        await page.fill('input', 'username');
        await page.click('button');
      });
    });
  });

  await browser.close();
})();

Conclusion

In conclusion, running some test cases in parallel and others sequentially is indeed feasible in Playwright. By identifying independent and interdependent tests, creating separate test suites, and using the `test.describe.parallel()` and `test.describe()` methods, you can implement a hybrid approach that optimizes your test execution time and resource allocation. Remember to carefully design your test suite to ensure that parallel and sequential tests are executed correctly and efficiently.

Scenario	Parallel Testing	Sequential Testing
Independent tests
Interdependent tests
Resource-intensive tests

By following the steps and examples outlined in this article, you’ll be able to harness the power of parallelism in Playwright while ensuring that your test suite is executed efficiently and effectively.

FAQs

1. Q: Can I run all tests in parallel using Playwright?

   A: Yes, you can run all tests in parallel using Playwright’s built-in support for parallel testing. However, this may not always be the most efficient approach, especially when dealing with interdependent tests.

2. Q: How do I ensure that parallel tests are executed correctly?

   A: To ensure that parallel tests are executed correctly, make sure to use unique browser contexts and pages for each test, and avoid sharing state between tests.

3. Q: Can I run sequential tests in parallel using Playwright?

   A: No, sequential tests should be executed one after the other to ensure that the results are accurate and reliable. Running sequential tests in parallel can lead to unpredictable results.

By implementing a hybrid approach to parallel and sequential testing in Playwright, you’ll be able to optimize your test execution time, reduce resource allocation, and ensure that your tests are executed efficiently and effectively.

Frequently Asked Question

In the world of automation testing, Playwright has revolutionized the way we write and execute tests. But, have you ever wondered if you can run part of your test cases parallelly and part of them sequentially at the same time in Playwright? Well, wonder no more! Here are the answers to your most pressing questions.