stack frame - each recursion call adds one to the call stack until it reaches the base case.
pytest.fixture
def reverse_lines(f):
return [one_line.rstrip()[::-1]+ '\n'
for one_line in f]
@pytest.fixture(scope='module')
def simple_file():
return StringIO('\n'.join(['abc', 'def', 'ghi', 'jkl']))
--cov