Part 1: Getting started
Part 1 of the tutorial explains how to set up a Python test automation project with pytest and Playwright.
What is Playwright?
Playwright is a new library that can automate interactions with Chromium, Firefox, and WebKit browsers via a single API.
It is an open source project developed by Microsoft.
Playwright is a fantastic alternative to Selenium WebDriver for web UI testing.
Like Selenium WebDriver, Playwright has language bindings in multiple languages: Python, .NET, Java, and JavaScript.
Playwright also refines many of the pain points in Selenium WebDriver.
Some examples include:
- Playwright interactions automatically wait for elements to be ready.
- Playwright can use one browser instance with multiple browser contexts for isolation instead of requiring multiple instances.
- Playwright has device emulation for testing responsive web apps in mobile browsers.
For a more thorough list of advantages, check out
Why Playwright?
from the docs.
Our web search test
For this tutorial, we will walk through one test scenario for DuckDuckGo searching.
DuckDuckGo is a search engine like Google or Yahoo.
The steps for a basic DuckDuckGo search are:
Given the DuckDuckGo home page is displayed
When the user searches for a phrase
Then the search result query is the phrase
And the search result links pertain to the phrase
And the search result title contains the phrase
Go to duckduckgo.com and give this a try.
You can use any search phrase you like.
It is important to write a test case before writing test code.
It is also important to try a test manually before attempting to automate it.
Test project setup
Let's set up the test project!
For this tutorial, we will build a new project from the ground up.
The GitHub repository should be used exclusively as a reference for example code.
Create a directory named playwright-python-tutorial for the project:
$ mkdir playwright-python-tutorial
$ cd playwright-python-tutorial
Inside this project, create a Python virtual environment
using the venv module
to manage dependency packages locally:
$ python3 -m venv venv
Creating a new virtual environment for each Python project is a recommended practice.
This command will create a subdirectory named venv that holds all virtual environment files, including dependency packages.
A note about Python commands:
Python has two incompatible major versions: 2 and 3.
Although Python 2 end-of-life was January 1, 2020, many machines still run it.
For example, macOS comes bundled with Python 2.7.18.
Sometimes, the python executable may point to Python 2 instead of 3.
To be precise about versions and executables, we will use the python3 and pip3 commands explicitly in this tutorial.
After creating a virtual environment, you must "activate" it.
On macOS or Linux, use the following command:
$ source venv/bin/activate
The equivalent command for a Windows command line is:
> venv\Scripts\activate.bat
You can tell if a virtual environment is active if its name appears in the prompt.
Let's add some Python packages to our new virtual environment:
$ pip3 install playwright
$ pip3 install pytest
$ pip3 install pytest-playwright
If you want to run the tests from this repository instead of creating a fresh project,
install the dependencies using this command:
$ pip3 install -r requirements.txt
By itself, Playwright is simply a library for browser automation.
We need a test framework like pytest if we want to automate tests.
The pytest-playwright
is a pytest plugin developed by the Playwright team that simplifies Playwright integration.
You can check all installed packages using pip3 freeze.
They should look something like this:
$ pip3 freeze
attrs==21.2.0
certifi==2021.10.8
charset-normalizer==2.0.8
greenlet==1.1.2
idna==3.3
iniconfig==1.1.1
packaging==21.3
playwright==1.19.1
pluggy==1.0.0
py==1.11.0
pyee==8.1.0
pyparsing==3.0.6
pytest==7.0.1
pytest-base-url==1.4.2
pytest-playwright==0.2.3
python-slugify==5.0.2
requests==2.26.0
text-unidecode==1.3
toml==0.10.2
tomli==2.0.1
urllib3==1.26.7
websockets==10.1
Notice that pip fetches dependencies of dependencies.
It is customary for Python projects to store this list of dependencies in a file named requirements.txt.
After the Python packages are installed, we need to install the browsers for Playwright.
The playwright install command installs the latest versions of the three browsers that Playwright supports:
Chromium, Firefox, and WebKit:
$ playwright install
By default, pytest with the Playwright plugin will run headless Chromium.
We will show how to run against other browsers in Part 5.
Finally, let's create a test function stub.
By Python conventions, all tests should be located under a tests directory.
Create a tests directory, and inside, create a file named test_search.py:
$ mkdir tests
$ touch tests/test_search.py
Add the following code to tests/test_search.py:
def test_basic_duckduckgo_search() -> None:
# Given the DuckDuckGo home page is displayed
# When the user searches for a phrase
# Then the search result query is the phrase
# And the search result links pertain to the phrase
# And the search result title contains the phrase
pass
The test_basic_duckduckgo_search is merely a stub, but it establishes good practices:
- It has a clear name.
- It defines the behavior to test step-by-step in its comments.
- It can be run immediately.
The pass statement at the end is just a no-op.
It does not mean "pass the test".
Remember, write test cases before you write test code.
Before continuing, run this test to make sure everything is set up correctly:
$ python3 -m pytest tests
pytest should discover, run, and pass the single test case under the tests directory.
A note about the pytest command:
Many online articles and examples use the pytest command directly to run tests, like this: pytest tests.
Unfortunately, this version of the command does not add the current directory to the Python path.
If your tests reference anything outside of their test modules, then the command will fail.
Therefore, I always recommend running the full python3 -m pytest tests command.
