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

问题描述

我正在寻找有关在抽象基类中定义的测试方法的方法/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，但有时这似乎有些过分.

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.

考虑这个例子:

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

正如 lunaryon 所说，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，可以创建一个实用函数来内省 ABC，并动态创建一个虚拟的非抽象类.这个函数可以直接在你的测试方法/函数中调用，这样你就不必为了测试一些方法而在测试文件中编写样板代码.

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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