Python-测试抽象基类 [英] Python - Testing an abstract base class

问题描述

我正在寻找有关测试抽象基类中定义的方法的方法/最佳实践.我可以直接想到的一件事是对基类的所有具体子类执行测试，但这在某些时候似乎很繁琐.

I am looking for ways / best practices on testing methods defined in an abstract base class. One thing I can think of directly is performing the test on all concrete subclasses of the base class, but that seems excessive at some times.

请考虑以下示例:

import abc

class Abstract(object):

    __metaclass__ = abc.ABCMeta

    @abc.abstractproperty
    def id(self):
        return   

    @abc.abstractmethod
    def foo(self):
        print "foo"

    def bar(self):
        print "bar"

是否可以在不进行任何子类化的情况下测试bar?

Is it possible to test bar without doing any subclassing?

推荐答案

lunaryon正确地指出，这是不可能的.包含抽象方法的ABC的真正目的是，它们不能像声明的那样实例化.

As properly put by lunaryon, it is not possible. The very purpose of ABCs containing abstract methods is that they are not instantiatable as declared.

但是，可以创建一个对ABC进行内省的实用函数，并即时创建一个虚拟的非抽象类.该函数可以在您的测试方法/函数中直接调用，省去了仅在测试文件中写一些样板代码就可以测试几种方法的麻烦.

However, it is possible to create a utility function that introspects an ABC, and creates a dummy, non abstract class on the fly. This function could be called directly inside your test method/function and spare you of having to wite boiler plate code on the test file just for testing a few methods.

def concreter(abclass):
    """
    >>> import abc
    >>> class Abstract(metaclass=abc.ABCMeta):
    ...     @abc.abstractmethod
    ...     def bar(self):
    ...        return None

    >>> c = concreter(Abstract)
    >>> c.__name__
    'dummy_concrete_Abstract'
    >>> c().bar() # doctest: +ELLIPSIS
    (<abc_utils.Abstract object at 0x...>, (), {})
    """
    if not "__abstractmethods__" in abclass.__dict__:
        return abclass
    new_dict = abclass.__dict__.copy()
    for abstractmethod in abclass.__abstractmethods__:
        #replace each abc method or property with an identity function:
        new_dict[abstractmethod] = lambda x, *args, **kw: (x, args, kw)
    #creates a new class, with the overriden ABCs:
    return type("dummy_concrete_%s" % abclass.__name__, (abclass,), new_dict)

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