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How to do unit testing in parallel in Python?

October 18, 2023 Leave a Comment

Unit testing in parallel using pytest

Running unit tests in parallel using pytest is a straightforward process, thanks to the built-in parallel test execution capabilities of pytest. You can use the -n option to specify the number of parallel processes or workers you want to use for test execution. Here’s how to run unit tests in parallel using pytest:

To do unit testing in parallel using pytest, you can use the pytest-xdist plugin. This plugin allows you to distribute your tests across multiple workers, which can significantly improve performance.

To install pytest-xdist, run the following command:

$ pip install pytest-xdist
Step 1 - Install pytest:

If you haven't already installed pytest, you can do so using pip:

$ pip install pytest

Step 2 - Organize Your pytest Tests:

def test_featureA():
    # Test code for feature A
    pass

def test_featureB():
    # Test code for feature B
    pass


Make sure you have organized your pytest tests into Python test files and functions as usual. pytest can automatically discover and execute your tests.

Step 3 - Run Tests in Parallel with pytest:

To run your pytest tests in parallel, use the pytest command followed by the -n option and the number of parallel processes you want to use. For example, to run tests in four parallel processes, use:

$ pytest -n 4

Step 4 - Replace 4 with the desired number of parallel processes you want to use.

pytest will discover your tests and distribute them across the specified number of processes for parallel execution. You'll see the test results from each process displayed in the terminal.

Step 5 - Customize Parallel Execution (Optional):

You can further customize parallel test execution using pytest by using various options and plugins. For example, you can use the -k option to select specific tests to run based on test names or patterns. You can also use pytest plugins to control test distribution and parallel execution in more detail.

Here's an example of running pytest with custom test selection:

$ pytest -n 4 -k "test_featureA or test_featureB"

In this example, only tests with names matching test_featureA or test_featureB will be selected for parallel execution.

Unit testing in parallel using unittest

To run unit tests in parallel using unittest, you can use the unittest-parallel package. This package allows you to distribute your tests across multiple threads or processes, which can significantly improve performance.

To install unittest-parallel, run the following command:

$ pip install unittest-parallel

Once unittest-parallel is installed, you can run your tests in parallel by specifying the --parallel option to unittest. The --parallel option can take one of the following values:

  • threads: Run tests in parallel using threads.
  • processes: Run tests in parallel using processes.
  • all: Run tests in parallel using all available threads and processes.

By default, unittest-parallel will run tests in parallel using threads. To run tests in parallel using processes, you can specify the --parallel=processes option.

For example, to run all of your tests in parallel using 4 threads, you would run the following command:

$ unittest --parallel=threads=4

You can also specify the --parallel-level option to control the level of parallelism. The --parallel-level option can take one of the following values:

  • test_case: Run each test case in parallel.
  • test_class: Run each test class in parallel.
  • test_suite: Run each test suite in parallel.
  • all: Run all test cases, classes, and suites in parallel.

By default, unittest-parallel will run tests in parallel at the test case level. To run tests in parallel at the test class level, you can specify the --parallel-level=test_class option.

For example, to run all of your tests in parallel at the test class level using 4 threads, you would run the following command:

$ unittest --parallel=threads=4 --parallel-level=test_class

You can also use unittest-parallel to run specific tests in parallel. To do this, you can specify the names of the tests to run in parallel using the --parallel-tests option.

For example, to run the TestSum and TestList test classes in parallel using 4 threads, you would run the following command:

$ unittest --parallel=threads=4 --parallel-tests=TestSum,TestList

unittest-parallel can be a very useful tool for improving the performance of your unit testing process. By running your tests in parallel, you can significantly reduce the time it takes to run your tests.

Here are some tips for running unit tests in parallel using unittest:

  • Make sure that your tests are independent of each other. If your tests are dependent on each other, you will not be able to run them in parallel.
  • Use fixtures to set up and tear down the state of your tests. This will help to ensure that your tests are isolated from each other.
  • Use the unittest-parallel package to distribute your tests across multiple threads or processes.
  • Specify the --parallel-level option to control the level of parallelism.
  • Use the --parallel-tests option to run specific tests in parallel.
import unittest
import multiprocessing

# Import your test classes here
from test_module import MyTestCase

# List of test classes to run
test_classes = [MyTestCase]

def run_tests(test_class):
    suite = unittest.TestLoader().loadTestsFromTestCase(test_class)
    unittest.TextTestRunner().run(suite)

if __name__ == '__main__':
    # Number of parallel processes
    num_processes = 4

    # Create a process pool
    pool = multiprocessing.Pool(processes=num_processes)

    # Run tests in parallel
    pool.map(run_tests, test_classes)

    # Close the pool
    pool.close()
    pool.join()

$ python test_runner.py

In this script:

  • Import your test classes.
  • Create a list of test classes to run.
  • Define a run_tests function that loads and runs tests from a test class.
  • Use multiprocessing.Pool to distribute the test classes across multiple processes and run them in parallel.
Rajesh Kumar
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