pytest_axe.py

# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this
# file, You can obtain one at http://mozilla.org/MPL/2.0/.

import re
import time
from os import environ

import pytest
from axe_selenium_python import Axe


# TODO: Strongly considering deprecating the pytest fixture.
# It adds complexity, and can only be applied to specific use cases.
@pytest.fixture
def axe(selenium, base_url):
    """Return an Axe instance to perform accessibility audits."""
    if base_url:
        selenium.get(base_url)
    yield PytestAxe(selenium)


# TODO: I am also unsure if a command line option adds any value.
# There are checks within axe-selenium-python for environement variables
# that can enable or disable accessibility tests and writing the results to
# file. If I keep this --axe flag, the aforementioned checks should be removed.
def pytest_addoption(parser):
    """Add command line option to filter run only accessibility tests."""
    parser.addoption(
        "--axe", action="store_true", default=False, help="run accessibility tests only"
    )


def pytest_collection_modifyitems(config, items):
    """Filter tests based on presence or absence of axe flag."""
    # TODO: figure out why reasons aren't printed when tests are skipped
    if config.getoption("--axe"):
        # --axe in cli: run accessibility tests and skip others
        skip_not_a11y = pytest.mark.skip(reason="run accessibility tests only.")
        for item in items:
            if "accessibility" not in item.keywords:
                item.add_marker(skip_not_a11y)
        return
    skip_a11y = pytest.mark.skip(reason="need --axe to run accessibility tests")
    for item in items:
        if "accessibility" in item.keywords:
            item.add_marker(skip_a11y)


class PytestAxe(Axe):
    def __init__(self, selenium, context=None, options=None, impact=None):
        """Instantiate Axe instance and set attributes."""
        super(PytestAxe, self).__init__(selenium)
        self.context = context
        self.options = options
        self.impact = impact

    def report(self, violations):
        """
        Return readable report of accessibility violations found.

        :param violations: Dictionary of violations.
        :type violations: dict
        :return report: Readable report of violations.
        :rtype: violations_report
        """
        violations_report = ""
        violations_report += (
            "Found " + str(len(violations)) + " accessibility violations:"
        )
        for violation, rule in violations.items():
            violations_report += (
                "\n\n\nRule Violated:\n"
                + rule["id"]
                + " - "
                + rule["description"]
                + "\n\tURL: "
                + rule["helpUrl"]
                + "\n\tImpact Level: "
                + rule["impact"]
                + "\n\tTags:"
            )
            for tag in rule["tags"]:
                violations_report += " " + tag
            violations_report += "\n\tElements Affected:"
            i = 1
            for node in rule["nodes"]:
                for target in node["target"]:
                    violations_report += "\n\t" + str(i) + ") Target: " + target
                    i += 1
                for item in node["all"]:
                    violations_report += "\n\t\t" + item["message"]
                for item in node["any"]:
                    violations_report += "\n\t\t" + item["message"]
                for item in node["none"]:
                    violations_report += "\n\t\t" + item["message"]
            violations_report += "\n\n\n"
        return violations_report

    def get_rules(self):
        """Return array of accessibility rules."""
        response = self.selenium.execute_script("return axe.getRules();")
        return response

    def run(self):
        """Inject aXe, run against current page, and return rules & violations."""
        self.inject()
        data = self.execute(self.context, self.options)
        violations = dict(
            (rule["id"], rule)
            for rule in data["violations"]
            if self.impact_included(rule)
        )

        return violations

    def run_single_rule(self, rule):
        """Configure options and run audit for a single accessibility rule."""
        self.inject()
        options = '{runOnly:{type: "rule", values: ["' + rule + '"]}}'
        self.options = options
        return self.run()

    def impact_included(self, rule):
        """Filter violations with specified impact level or higher."""
        impact = self.impact
        if impact == "minor" or impact is None:
            return True
        elif impact == "moderate" & rule["impact"] != "minor":
            return True
        elif impact == "serious":
            if rule["impact"] == "serious" or rule["impact"] == "critical":
                return True
        elif impact == "critical" and rule["impact"] == "critical":
            return True
        else:
            return False

    def analyze(self):
        """Run aXe accessibility checks, and write results to file."""
        violations = self.run()

        # Format file name based on page title and current datetime.
        t = time.strftime("%m_%d_%Y_%H:%M:%S")
        title = self.selenium.title
        title = re.sub("[\s\W]", "-", title)
        title = re.sub("(-|_)+", "-", title)

        # Output results only if reporting is enabled.
        if environ.get("ACCESSIBILITY_REPORTING") == "true":
            # Write JSON results to file if recording enabled
            self.write_results("%s_%s.json" % (title, t), violations)
        assert len(violations) == 0, self.report(violations)