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对告警进行断言，可以通过with语句对告警的类型进行断言，如下，即断言代码中会产生UserWarning类型的告警。
```python
import pytest
import warnings

def test_demo():
    print("in test_demo ...")
    with pytest.warns(UserWarning):
        warnings.warn(UserWarning("warning，used to demo..."))
```
执行结果如下，即断言通过。
```bash
(demo-HCIhX0Hq) E:\demo>pytest -s
=================== test session starts ===================
platform win32 -- Python 3.7.9, pytest-7.2.0, pluggy-1.0.0
rootdir: E:\demo, configfile: pytest.ini
plugins: assume-2.4.3, rerunfailures-10.2
collected 1 item

test_demo.py in test_demo ...
.

==================== 1 passed in 0.02s ====================

(demo-HCIhX0Hq) E:\demo>
```
将测试代码修改为如下代码，即在代码中抛出SyntaxWarning类型的告警，而断言期望的是UserWarning类型的告警。
```python
import pytest
import warnings

def test_demo():
    print("in test_demo ...")
    with pytest.warns(UserWarning):
        warnings.warn(SyntaxWarning("warning，used to demo..."))
```
执行结果如下，即此时报错了，显示并未有UserWarning类型的告警产生。
```bash
(demo-HCIhX0Hq) E:\demo>pytest -s
=================== test session starts ===================
platform win32 -- Python 3.7.9, pytest-7.2.0, pluggy-1.0.0
rootdir: E:\demo, configfile: pytest.ini
plugins: assume-2.4.3, rerunfailures-10.2
collected 1 item

test_demo.py in test_demo ...
F

======================== FAILURES =========================
________________________ test_demo ________________________

def test_demo():
        print("in test_demo ...")
        with pytest.warns(UserWarning):
>           warnings.warn(SyntaxWarning("warning，used to demo..."))
E           Failed: DID NOT WARN. No warnings of type (<class 'UserWarning'>,) were emitted.
E           The list of emitted warnings is: [SyntaxWarning('warning，used to demo...')].

test_demo.py:8: Failed
================= short test summary info =================
FAILED test_demo.py::test_demo - Failed: DID NOT WARN. No warnings of type (<class 'User...
==================== 1 failed in 0.07s ====================

(demo-HCIhX0Hq) E:\demo>
```
此外，还可以通过正则表达式对告警内容进行断言，如下即判断告警内容中含有demo。
```python
import pytest
import warnings

def test_demo():
    print("in test_demo ...")
    with pytest.warns(UserWarning,match=r'.*demo.*'):
        warnings.warn(UserWarning("warning，used to demo..."))
```
执行结果如下，即断言通过。
```bash
(demo-HCIhX0Hq) E:\demo>pytest -s
=================== test session starts ===================
platform win32 -- Python 3.7.9, pytest-7.2.0, pluggy-1.0.0
rootdir: E:\demo, configfile: pytest.ini
plugins: assume-2.4.3, rerunfailures-10.2
collected 1 item

test_demo.py in test_demo ...
.

==================== 1 passed in 0.02s ====================

(demo-HCIhX0Hq) E:\demo>
```
初次以为，还可以对函数调用中的告警类型进行断言，如下即断言add函数中会产生UserWarning类型的告警，同时，add函数需要给定两个参数a和b。
```python
import pytest
import warnings

def add(a,b):
    print("a:",a)
    print("b:",b)
    warnings.warn(UserWarning("warning，used to demo..."))

def test_demo():
    print("in test_demo ...")
    pytest.warns(UserWarning,add,10,20)
```
执行结果如下，可以看出，参数a和b能够正常传入，而且也做到了对函数中产生的告警类型的断言。
```bash
(demo-HCIhX0Hq) E:\demo>pytest -s
=================== test session starts ===================
platform win32 -- Python 3.7.9, pytest-7.2.0, pluggy-1.0.0
rootdir: E:\demo, configfile: pytest.ini
plugins: assume-2.4.3, rerunfailures-10.2
collected 1 item

test_demo.py in test_demo ...
a: 10
b: 20
.

==================== 1 passed in 0.02s ====================

(demo-HCIhX0Hq) E:\demo>

```

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