Select the test case.

def _select_case(self, role, case):
        """Select the test case.
        """
        # select the case
        elem = Select(self._browser.find_element_by_id('select-dut'))
        elem.select_by_value(str(role))
        time.sleep(1)

        checkbox = None
        wait_until(lambda: self._browser.find_elements_by_css_selector('.tree-node .tree-title') and True)
        elems = self._browser.find_elements_by_css_selector('.tree-node .tree-title')
        finder = re.compile(r'.*\b' + case + r'\b')
        finder_dotted = re.compile(r'.*\b' + case.replace(' ', r'\.') + r'\b')
        for elem in elems:
            action_chains = ActionChains(self._browser)
            action_chains.move_to_element(elem)
            action_chains.perform()
            logger.debug(elem.text)
            if finder.match(elem.text) or finder_dotted.match(elem.text):
                parent = elem.find_element_by_xpath('..')
                checkbox = parent.find_element_by_class_name('tree-checkbox')
                break

        if not checkbox:
            time.sleep(5)
            raise Exception('Failed to find the case')

        self._browser.execute_script("$('.overview').css('left', '0')")
        checkbox.click()
        time.sleep(1)

        elem = self._browser.find_element_by_id('runTest')
        elem.click()
        if not wait_until(lambda: self._browser.find_element_by_id('stopTest') and True, 10):
            raise Exception('Failed to start test case')