pytest-needle

Example

Example needle pytest implementation:

"""test_example.py
"""

from selenium.webdriver.common.by import By
import pytest

@pytest.mark.element
def test_example_element(needle):
    """Example for comparing individual elements

    :param NeedleDriver needle: NeedleDriver instance
    :return:
    """

    # Navigate to web page
    needle.driver.get('https://www.google.com')

    # Take an element screen diff
    needle.assert_screenshot('search_field', (By.ID, 'tsf'))

To create a baseline for all subsequent test run:

pytest --driver Chrome --needle-save-baseline test_example.py

After we have a baseline, to run test use:

pytest --driver Chrome test_example.py

Selecting a WebDriver

To control which browser to use, use --driver <BROWSER> from pytest-selenium. For example to change to browser to Firefox:

pytest --driver Firefox test_example.py

Setting the viewport’s size

You may set the size of the browser’s viewport using the set_viewport_size() on the needle fixture

def test_example_viewport(needle):

    # Navigate to web page
    needle.set_viewport_size(width=1024, height=768)

    # Rest of the test ...

You may also set the default viewport size for all your tests by using the command line argument --needle-viewport-size:

pytest --driver Chrome --needle-viewport-size "1024 x 768" test_example.py

Excluding areas

Sometimes areas on a web page may contain dynamic content and cause false negatives, or worse convince testers to raise the threshold at which changes are acceptable. You can instead choose to mask these areas to avoid the issue of consistently failing tests:

"""test_example.py
"""

from selenium.webdriver.common.by import By
import pytest


@pytest.mark.mask
def test_example_page_with_mask(needle):
    """Example for comparing page with a mask

    :param NeedleDriver needle: NeedleDriver instance
    :return:
    """

    # Navigate to web page
    needle.driver.get('https://www.google.com')

    # Take a entire page screen diff, ignore the doodle banner
    needle.assert_screenshot('search_page', threshold=60, exclude=[(By.ID, 'hplogo'), (By.ID, 'prm')])

In the case with Google’s home page the doodle banner frequently changes, so to visually regress day-to-day requires generating new baselines every time the banner is updated. Masking allows only the banner to be ignored while the rest of the page can be evaluated.