# Test helpers
# test_raises
Context manager for testing exceptions. More ergonomic than `test_fail`
for multi-line code blocks and allows optional message content
validation.
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### test_raises
``` python
def test_raises(
expected:Type[Exception], contains:str | None=None
):
```
``` python
with test_raises(ZeroDivisionError):
1/0 # type: ignore
with test_raises(ZeroDivisionError, 'division by zero'):
1/0 # type: ignore
```
# test_afail
Async version of
[`fastcore.test.test_fail`](https://fastcore.fast.ai/test.html#test_fail).
Test that an async function raises an exception.
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### test_afail
``` python
async def test_afail(
f, msg:str='', contains:str='', args:NoneType=None, kwargs:NoneType=None
):
```
Like fastcore own ‘test_fail’, but async
# test_is_not
Test that two objects are not the same instance. Complement to
[`fastcore.test.test_is`](https://fastcore.fast.ai/test.html#test_is).
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### test_is_not
``` python
def test_is_not(
a, b
):
```
*`test` that `a is not b`*
##