reorder pytest tests based on dependencies

conftest.py

def pytest_collection_modifyitems(session, config, items):
    """Reorder the execution of tests based on the dependency marks on tests.
    
    To setup a test dependency, decorate the test function with the "depends" 
    mark and give a list of dependencies via the "on" keyword arg to the 
    decorator. Dependencies can be specified by name only when in the same
    file as the test being decorated, or by pytest node path for tests in 
    other files/classes.
    
        @pytest.mark.depends(on=["test_in_same_file", 
                                 "test_other.py::test_in_other_file", 
                                 "test_other.py::TestClass::test_method"])
        def test_with_dependencies():
            pass
            
    Tests without dependencies will run in arbitrary order.            
    """
    def _nodeid_cleaner(nodeid):
        """Clean node ids for class-based tests so they're easier to refer to."""
        return nodeid.replace('::()::', '::')

    dag = nx.DiGraph()

    nodeid_to_item_map = {_nodeid_cleaner(item.nodeid): item for item in items}

    list(map(lambda x: dag.add_node(_nodeid_cleaner(x.nodeid)), items))

    for item in items:
        marker = item.get_closest_marker("depends")
        if marker is not None:
            depends = marker.kwargs.get('on', [])
            for dependency in depends:
                if '::' not in dependency:
                    base_item_nodeid = _nodeid_cleaner(item.nodeid).rsplit('::', 1)[0]
                    dependency = f"{base_item_nodeid}::{dependency}"
                dag.add_edge(dependency, _nodeid_cleaner(item.nodeid))

    reordered = [nodeid_to_item_map[node] for node in nx.topological_sort(dag)]

    items[:] = reordered

requirements.pip

pytest
networkx