自动化框架的两种断言设计(pytest 版)

自动化测试断言失败时，根据不同业务场景，可能需要立即终止或继续执行。这里以 Appium + pytest 为例。

一. 断言失败立即终止

用途一：用例的预期结果是其他用例的前提条件时，assert 失败需要立即终止，这是我们设计自动化测试用例时最常见的场景。

用途二：用例中的任何一个步骤执行失败时，立即终止，因为步骤都执行失败了，没有继续执行下一步的必要。方案：思路与用途一类似，这里把每个测试步骤当做都有一个预期结果(True)，封装每一个具体步骤，步骤结果返回布尔值。对该结果进行 assert，False时立即终止。

 def click(self, step):

     method_name = sys._getframe().f_code.co_name

     try:

         element = self.find_element(**step['element_loc'])

         if step.has_key('times'):

             for i in range(step['times']):

                 element.click()

         else:

             element.click()

         return True

     except:

         print u'%s失败' % method_name

         return False

 for step in self.case_steps:

     assert self.operate(step), 'error in step: %s' % step

二. 断言失败继续执行

主要使用了两个函数 expect, assert_expectations 。

Demo: test_delayed_assert.py

 from delayed_assert import expect, assert_expectations

 def test_should_pass():

     expect(1 == 1, 'one is one')

     assert_expectations()

 def test_should_fail():

     expect(1 == 2)

     x = 1

     y = 2

     expect(x == y, 'x:%s y:%s' % (x,y))

     expect(1 == 1)

     assert_expectations()

Module: delayedAssert.py

 '''

 Implements one form of delayed assertions.

 Interface is 2 functions:

   expect(expr, msg=None)

   : Evaluate 'expr' as a boolean, and keeps track of failures

   assert_expectations()

   : raises an assert if an expect() calls failed

 Usage Example:

     from expectations import expect, assert_expectations

     def test_should_pass():

         expect(1 == 1, 'one is one')

         assert_expectations()

     def test_should_fail():

         expect(1 == 2, 'one is two')

         expect(1 == 3, 'one is three')

         assert_expectations()

 '''

 # ---------------------------------------------------

 def expect(expr, msg=None):

     'keeps track of failed expectations'

     if not expr:

         _log_failure(msg)

 def assert_expectations():

     'raise an assert if there are any failed expectations'

     if _failed_expectations:

         assert False, _report_failures()

 # ---------------------------------------------------

 import inspect

 import os.path

 _failed_expectations = []

 def _log_failure(msg=None):

     (filename, line, funcname, contextlist) =  inspect.stack()[2][1:5]

     filename = os.path.basename(filename)

     context = contextlist[0]

     _failed_expectations.append('file "%s", line %s, in %s()%s\n%s' %

         (filename, line, funcname, (('\n%s' % msg) if msg else ''), context))

 def _report_failures():

     global _failed_expectations

     if _failed_expectations:

         (filename, line, funcname) =  inspect.stack()[2][1:4]

         report = [

             '\n\nassert_expectations() called from',

             '"%s" line %s, in %s()\n' % (os.path.basename(filename), line, funcname),

             'Failed Expectations:%s\n' % len(_failed_expectations)]

         for i,failure in enumerate(_failed_expectations, start=1):

             report.append('%d: %s' % (i, failure))

         _failed_expectations = []

     return ('\n'.join(report))

 # ---------------------------------------------------

 # _log_failure() notes

 #

 # stack() returns a list of frame records

 #   0 is the _log_failure() function

 #   1 is the expect() function

 #   2 is the function that called expect(), that's what we want

 #

 # a frame record is a tuple like this:

 #   (frame, filename, line, funcname, contextlist, index)

 # we're mainly interested in the middle 4,

 # ---------------------------------------------------

参考：Delayed assert / multiple failures per test