python - How can I repeat each test multiple times in a py.test run?

Question

I want to run each selected py.test item an arbitrary number of times, sequentially.
I don't see any standard py.test mechanism for doing this.

I attempted to do this in the pytest_collection_modifyitems() hook. I modified the list of items passed in, to specify each item more than once. The first execution of a test item works as expected, but that seems to cause some problems for my code.

Further, I would prefer to have a unique test item object for each run, as I use id (item) as a key in various reporting code. Unfortunately, I can't find any py.test code to duplicate a test item, copy.copy() doesn't work, and copy.deepcopy() gets an exception.

Can anybody suggest a strategy for executing a test multiple times?

question from:https://stackoverflow.com/questions/21764473/how-can-i-repeat-each-test-multiple-times-in-a-py-test-run

Answer 1

In order to run each test a number of times, we will programmatically parameterize each test as the tests are being generated.

First, let's add the parser option (include the following in one of your conftest.py's):

def pytest_addoption(parser):
    parser.addoption('--repeat', action='store',
        help='Number of times to repeat each test')

Now we add a "pytest_generate_tests" hook. Here is where the magic happens.

def pytest_generate_tests(metafunc):
    if metafunc.config.option.repeat is not None:
        count = int(metafunc.config.option.repeat)

        # We're going to duplicate these tests by parametrizing them,
        # which requires that each test has a fixture to accept the parameter.
        # We can add a new fixture like so:
        metafunc.fixturenames.append('tmp_ct')

        # Now we parametrize. This is what happens when we do e.g.,
        # @pytest.mark.parametrize('tmp_ct', range(count))
        # def test_foo(): pass
        metafunc.parametrize('tmp_ct', range(count))

Running without the repeat flag:

(env) $ py.test test.py -vv
============================= test session starts ==============================
platform darwin -- Python 2.7.5 -- py-1.4.20 -- pytest-2.5.2 -- env/bin/python
collected 2 items 

test.py:4: test_1 PASSED
test.py:8: test_2 PASSED

=========================== 2 passed in 0.01 seconds ===========================

Running with the repeat flag:

(env) $ py.test test.py -vv --repeat 3
============================= test session starts ==============================
platform darwin -- Python 2.7.5 -- py-1.4.20 -- pytest-2.5.2 -- env/bin/python
collected 6 items 

test.py:4: test_1[0] PASSED
test.py:4: test_1[1] PASSED
test.py:4: test_1[2] PASSED
test.py:8: test_2[0] PASSED
test.py:8: test_2[1] PASSED
test.py:8: test_2[2] PASSED

=========================== 6 passed in 0.01 seconds ===========================

Further reading:

• https://pytest.org/latest/plugins.html#well-specified-hooks
• https://pytest.org/latest/example/parametrize.html