def METHOD_NAME(self):
    """The cache stores eclass mtimes and regenerates entries if they differ."""
    eclass_path = pjoin(self.eclass_dir, "foo.eclass")
    touch(eclass_path)
    self.addon.update_cache()
    assert list(self.addon.eclasses) == ["foo"]
    sleep(1)
    with open(eclass_path, "w") as f:
        f.write("# changed eclass\n")
    with patch("pkgcheck.addons.caches.CachedAddon.save_cache") as save_cache:
        self.addon.update_cache()
        save_cache.assert_called_once()