Wrap each pytest test function into try-except

Question

I want to wrap each of my test functions into a try-except block to execute code in the except block. This code should only be executed if the test is failing.

I want to achieve this without altering the test functions, but instead use some kind of decorator/fixture. Unfortunately I can not find any examples.

Example of what I'm trying to achieve:

def test_1():
    some_method_that_might_throw_an_exception()

I have multiple tests and all of them should run a function run_only_if_exception_was_thrown() if an exception was thrown by the test. I want to achieve this without using a try/catch block inside the tests.

My current approach is to use sys.last_value inside a fixture to check if an exception was thrown:

@pytest.fixture
def fix():
    yield X()
    try:
        if sys.last_value:
            # error
    except AttributeError:
            # no error thrown

def test1(fix):
    some_method_that_might_throw_an_exception()

Could you add an example what you're trying to do? – MSeifert May 12 '17 at 12:32 — MSeifert, May 12 '17 at 12:32

themiurge · Accepted Answer · 2017-05-12T13:17:28.120

4

How about this:

def test_dec(test_func):
    def test_wrapper(fix):
        try:
            test_func(fix)
        except:
            run_only_if_exception_was_thrown(fix)
            # re-raise exception to make the test fail
            raise

    return test_wrapper

Then in your test suite:

...
@test_dec
def test_one(fix):
    # test code

edited May 12 '17 at 13:17

answered May 12 '17 at 12:47

themiurge

1,619
17
21

How would this code look if `test_one` had a fixture argument? – user1211030 May 12 '17 at 12:56
I edited my answer. The decorator handles arbitrary parameters. – themiurge May 12 '17 at 13:04
I want to use the object passed to the test function inside the decorator. e.g. `run_only_if_exception_was_thrown(fix)` Is there a way to achieve that? – user1211030 May 12 '17 at 13:13
1

Oh, I see. Edited my answer. – themiurge May 12 '17 at 13:17
@user1211030 Could you explain what you were using this for? I'm just curious. – Connor Sep 01 '18 at 22:27

Wrap each pytest test function into try-except

1 Answers1

Linked