Implement link checker #67

from hypothesis.stateful import GenericStateMachine
import hypothesis.strategies as st
from requests_html import HTMLSession


class LinkChecker(GenericStateMachine):
    def __init__(self):
        super(LinkChecker, self).__init__()
        self.session = HTMLSession()
        self.result = None

    def steps(self):
        if self.result is None:
            # Always start on the home page
            return st.just("https://hypothesis.works/")
        else:
            return st.sampled_from([
                l
                for l in self.result.html.absolute_links
                # Don't try to crawl to other people's sites
                if l.startswith("https://hypothesis.works") and
                # Avoid Cloudflare's bot protection. We are a bot but we don't
                # care about the info it's hiding.
                '/cdn-cgi/' not in l
            ])

    def execute_step(self, step):
        self.result = self.session.get(step)

        assert self.result.status_code == 200

        for l in self.result.html.absolute_links:
            # All links should be HTTPS
            assert "http://hypothesis.works" not in l


TestLinks = LinkChecker.TestCase