Adding testcase dynamically before start of testing

[Stefanhg]

Hello,
I want to add a custom testcase to the pytest_collection_modifyitems items list before my test session starts depending on a variable set in the pytest config.

I played around with different functions and got stuck at this from_parent function which I haven't had any success with.
I do have a "work-around" which is just including it with -k and give a warning if variable is set in config and the testcase is missing in collector but what's the fun in that!

My goal is to:

1. Add the testcase to the testsuite,
2. To have it as the first testcase in the testsuite.

Simplified example of what i want to do, it is kind of hard to show when you don't know how to implement.
I am unsure if it is even possible to do this way or it has to go though the collector.

# test_mytests.py
def test_first_test(): pass

def test_dynamic_test(): pass

# conftest.py
def pytest_collection_modifyitems(session, config, items):
    item = add_testcase_to_current_testsuite(obj=test_dynamic_test, name="test_dynamic_test")
    items.insert(0, item)