TestNG vs pytest: What are the differences?

Introduction

TestNG and pytest are two popular testing frameworks used in software testing. While both frameworks serve the same purpose of automated testing, they have some key differences that set them apart. In this article, we will discuss the six main differences between TestNG and pytest.

1. Test Execution Model: TestNG follows a suite-test-method hierarchy for test execution. It allows the grouping of tests into classes, which are organized within test suites. On the other hand, pytest follows a more flexible and streamlined approach. It automatically discovers and executes tests based on naming conventions and allows the use of test functions or test classes without any specific hierarchy.

2. Fixture Management: Pytest has a more powerful and flexible fixture management mechanism compared to TestNG. Fixtures in pytest allow the setup and teardown of test resources, such as creating database connections or setting up test data. TestNG, on the other hand, uses annotations like @BeforeTest and @AfterTest to define setup and teardown methods.

3. Test Parameterization: Parameterization of tests is more straightforward in pytest compared to TestNG. Pytest allows the use of decorators such as @pytest.mark.parametrize to define multiple test inputs and expected outputs. TestNG uses data providers for parameterization, which require an additional setup for data feeding.

4. Test Reporting: TestNG provides comprehensive testing reports by default, including passed, failed, and skipped tests, along with time and status. It also supports various report formats like HTML and XML. Pytest, on the other hand, offers minimalistic reporting by default. However, it provides a rich ecosystem of plugins that can generate detailed and customized reports.

5. Parallel Execution: TestNG has built-in support for parallel test execution, allowing tests to run concurrently on multiple threads or machines. It provides annotations like @Test(threadPoolSize) to specify the number of threads for parallel execution. Pytest also supports parallel test execution through plugins like pytest-xdist. However, it requires additional setup and configuration compared to TestNG.

6. Test Discovery: Pytest has a powerful test discovery mechanism that automatically discovers and executes tests from a directory or module. It uses naming conventions and explicit test markers to identify and run tests. TestNG, on the other hand, requires manual configuration and explicit inclusion of test classes or methods in test suite XML files for test discovery.

In summary, TestNG and pytest differ in their test execution model, fixture management, test parameterization, test reporting, parallel execution support, and test discovery mechanism. Understanding these differences is crucial in choosing the right testing framework for your project.