Running Parameterized Tests with Nose2

nose2 is a Python testing framework like PyTest and unittest. In fact, nose2 is built on top of unittest and supports the use of multiple plugins. These plugins allow the abstraction of test steps necessary for each test. As a result, the plugins also help reduce redundancy. Since nose2 is built on top of unittest, it allows you to use and extend your existing test suite. All the basic features are built as plugins which you can choose to exclude or include. These features can include Test discovery, Parameterized Tests, Filtering Tests and so on.

In this guide, we will use an existing unit test and parameterize it. The test would open a search engine and do a search. The name of the search engine would be a parameter. This short exercise will allow us to bundle multiple test cases with the same logic into one test with use of parameters.

Installation

nose2 installation entails installing a pip package. It can be installed using the following command.

This will install the latest version of nose2 in your python development environment.

Writing a Test Case

We will write a test case to do a google search for a keyword. We will start by importing the necessary modules. We will need to importselenium and unittest to create a driver and write a test case respectively.

To begin writing the test case, we will need to put it in a unittest.TestCase class. Create a class which extends unittest.TestCase

The test class will contain a method beginning with test_ substring to be detected as a test by nose2. We will create a selenium driver and navigate to the website. After that, we will find the search bar using its xPath and execute a search.

We will create a main method in this module which will import nose2 and run the test above.

Putting it altogether, your test module should look like this.

Now, you can run this test by running the python module.

Parameterizing the Test Case

To parameterize the test case implies that we run the the test case using variables whose values can be changed during test execution. Instead of having to write the same test case for multiple search engines, we can reuse the same code and just change the website url along with the selector. nose2 allows you to do this with a built-in plugin called nose2.tools.params.

We will use this plugin in a new test case and parametrize the search engine along with the selector.

The code above is broken down by the following bullet points

• As you can see, we have reused the old test case. We have replaced the hardcoded xPath selector with the function decorator.
• The function decorator @params takes a series of tuples. Each tuple maps to the newly added parameters in the function signature.
• In this way, the above test case will actually run 3 test cases. Each test run it will change the value of the search_engine and xpath parameter based on the values provided.

You can run this module in the exact same manner as before.

Conclusion

In this short guide, we updated our existing unittest module and ran it with nose2. After that, we imported a default nose2 plugin to parameterize the test cases. In this way we were able to use plugins with our existing test cases without much modification. Similarly, nose2 also allows you to modify the test reporting logic or use plugins to run test in parallel.

Lastly, if you have any questions on this blog post, you can reach out to us by joining our Discord server:

Join the Tauk Discord Server!