对于测试覆盖，我想测试文件'signalC'中该函数的异常块：

class SignalC:

def readSignal(self, a):

try:

with open(os.path.join(self.newSubFolder, "my file" + '.csv'), 'a') as csvfile:

writer = csv.writer(csvfile, delimiter=',', quotechar='|',

quoting=csv.QUOTE_MINIMAL, lineterminator='\n')

print 'Reading'

z = random.uniform(-0.1, 0.1)

readValue = z + setP[element]

writer.writerow([self.element + '-' + str(element+1),)

except IOError as message:

logging.error('Error in writing the csv file ' + str(message))

print(message.strerror)

raise IOError

到目前为止，我尝试了这种方法，但仍然无法进入异常块：

def testReadSignal(self):

sc = signalC.SignalC()

a = [1, 1, 1]

with mock.patch("signalC.SignalC.readSignal", side_effect=IOError("IOError")):

self.assertRaises(IOError, sc.readSignal, a)

或者我应该用错误的输入引发异常？谁能举一个例子？提前致谢