:Test Suite:

原始碼中只提供了addtest的方法新增需要執行的用例到容器中，沒有提供從容器中移走某個用例的方法，其實很好理解，只需要用到remove函式就能實現了。具體的改造也只是將append改成remove即可

    def delTest(self, test):
        # sanity checks
        if not hasattr(test, '__call__'):
            raise TypeError("{} is not callable".format(repr(test)))
        if isinstance(test, type) and issubclass(test,
                                                 (case.TestCase, TestSuite)):
            raise TypeError("TestCases and TestSuites must be instantiated "
                            "before passing them to addTest()")
        self._tests.remove(test)