如何使用Python的unittest来声明数据库错误？

Question

我正在运行Python 2.6.5，因此我使用unittest2模块，它是2.7和3.X中unittest模块的未来端口。我正在执行以下集成测试：

def test_hits_constraint_raise(self): 
    obj = Table1(...) 
    self.sess.add(obj) 
    self.sess.flush() 

    # assert condition raises 
    self.assertFailure(IntegrityError, sess.add, obj) 

取而代之，它遇到了错误。

====================================================================== 
ERROR: test_hits_constraint_raise (__main__.TestModels) 
---------------------------------------------------------------------- 
Traceback (most recent call last): 
    File "test_models.py", line 76, in test4_create_exercise_same_id_constraint_raise 
    self.sess.flush() 
    File "build/bdist.linux-i686/egg/sqlalchemy/orm/scoping.py", line 114, in do 
    return getattr(self.registry(), name)(*args, **kwargs) 
     ......... 
    File "build/bdist.linux-i686/egg/sqlalchemy/engine/default.py", line 331, in do_execute 
    cursor.execute(statement, parameters) 
IntegrityError: (IntegrityError) column exercise_id is not unique u'INSERT INTO TABLE1 (attribute1_name, attribute2_name) VALUES (?, ?)' ('value1', 'value2') 

---------------------------------------------------------------------- 
Ran 4 tests in 0.531s 

FAILED (errors=1) 

唯一的办法是使用@unittest2.expectedFailure？那个会运行良好。 但我想知道到底发生了什么样的错误。

---------------------------------------------------------------------- 
Ran 4 tests in 0.513s 

OK (expected failures=1) 

Answer 1

您可以使用assertRaises为with声明背景：

with unittest.assertRaises(IntegrityError): 
    sess.add(obj) 

More details。