pytest-pyodide 0.21.1

"Pytest plugin for testing applications that use Pyodide"

pytest-pyodide

Pytest plugin for testing applications that use Pyodide

Installation

pytest-pyodide requires Python 3.10+ and can be installed with

pip install pytest-pyodide

You would also one at least one of the following runtimes,

• Chrome and chromedriver
• Firefox and geckodriver
• node v14+

Usage

1. First you would need a compatible version of Pyodide. You can download the Pyodide build artifacts from releases with,

   wget https://github.com/pyodide/pyodide/releases/download/0.21.0/pyodide-build-0.21.0.tar.bz2
   tar xjf pyodide-build-0.21.0.tar.bz2
   mv pyodide dist/
   

2. You can then use the provided fixtures (selenium, selenium_standalone) in tests,

   def test_a(selenium):
       selenium.run("assert 1+1 == 2")   # run Python with Pyodide
   

   which you can run with

   pytest --dist-dir=./dist/
   

run_in_pyodide

Some tests simply involve running a chunk of code in Pyodide and ensuring it doesn't error. In this case, one can use the run_in_pyodide decorate from pytest_pyodide, e.g.

from pytest_pyodide import run_in_pyodide
@run_in_pyodide
def test_add(selenium):
    assert 1 + 1 == 2

In this case, the body of the function will automatically be run in Pyodide. The decorator can also be called with a packages argument to load packages before running the test. For example:

from pytest_pyodide import run_in_pyodide
@run_in_pyodide(packages = ["regex"])
def test_regex(selenium_standalone):
    import regex
    assert regex.search("o", "foo").end() == 2

You can also use @run_in_pyodide with pytest.mark.parametrize, with hypothesis, etc. @run_in_pyodide MUST be the innermost decorator. Any decorators inside of @run_in_pyodide will be have no effect on the behavior of the test.

from pytest_pyodide import run_in_pyodide
@pytest.mark.parametrize("x", [1, 2, 3])
@run_in_pyodide(packages = ["regex"])
def test_type_of_int(selenium, x):
    assert type(x) is int

These arguments must be picklable. You can also use fixtures as long as the return values of the fixtures are picklable (most commonly, if they are None). As a special case, the function will see the selenium fixture as None inside the test.

It is possible to use run_in_pyodide as an inner function:

def test_inner_function(selenium):
    @run_in_pyodide
    def inner_function(selenium, x):
        assert x == 6
        return 7
    assert inner_function(selenium_mock, 6) == 7

Again both the arguments and return value must be pickleable.

Also, the function will not see closure variables at all:

def test_inner_function_closure(selenium):
    x = 6
    @run_in_pyodide
    def inner_function(selenium):
        assert x == 6
        return 7
    # Raises `NameError: 'x' is not defined`
    assert inner_function(selenium_mock) == 7

Specifying a browser

You can specify a browser runtime using --runtime (--rt) commandline option.

Possible options for --runtime are:

• node (default)
• firefox
• chrome
• all (chrome + firefox + node)
• host (do not run browser-based tests)

pytest --runtime firefox

Running tests with Playwright (optional)

By default, the tests will be run with Selenium. It is possible to run tests with playwright instead as follows.

First install playwright browsers

python -m playwright install --with-deps

Then use the --runner argument to specify to run tests with playwright.

pytest --runner playwright

Custom test marks

Custeom test marks supported by pytest-pyodide:

pytest.mark.driver_timeout(timeout): Set script timeout in WebDriver. If the test is known to take a long time, you can extend the deadline with this marker.

pytest.mark.xfail_browsers(chrome="why chrome fails"): xfail a test in specific browsers.

Examples

See examples.

License

pytest-pyodide uses the Mozilla Public License Version 2.0.