'Test link for `Return to Annotation` appears if and only if
the flag is set.'

def test_return_to_annotation(self):

    xpath = "//a[@class='annotation-return']"
    self.context['return_to_annotation'] = True
    xml = self.render_to_xml(self.context)
    self.assert_has_xpath(xml, xpath, self.context)
    self.context['return_to_annotation'] = False
    xml = self.render_to_xml(self.context)
    self.assert_no_xpath(xml, xpath, self.context)
