Python pytest不显示断言差异

以下测试:

def test_something():
    assert "ddd" == "pepe"

使用pytest运行时会显示以下错误消息:

E       AssertionError: assert 'ddd' == 'pepe'
E         - ddd
E         + pepe

但是,如果我们将assert方法移动到另一个文件 assertion.py

class CustomerAssertor(object):
    def __init__(self,name):
        self.name =name

    def assert_name(self,expected):
        assert self.name ==expected

我们把测试改为:

from sql_gen.test.utils.assertion_util import CustomerAssertor

def test_something():
    CustomerAssertor("ddd").assert_name("pepe")

现在我得到以下错误:

self = <assertions.CustomerAssertor object at 0x7fbcc3d31588>, expected = 'pepe'

    def assert_name(self,expected):
>       assert self.name ==expected
E       AssertionError

这条消息没有告诉你名字的价值是什么,那么信息量就少了,为什么?