index.rst

Fixtures

event_loop

Creates a new asyncio event loop based on the current event loop policy. The new loop is available as the return value of this fixture for synchronous functions, or via asyncio.get_running_loop for asynchronous functions. The event loop is closed when the fixture scope ends. The fixture scope defaults to function scope.

Note that, when using the event_loop fixture, you need to interact with the event loop using methods like event_loop.run_until_complete. If you want to await code inside your test function, you need to write a coroutine and use it as a test function. The asyncio marker is used to mark coroutines that should be treated as test functions.

If you need to change the type of the event loop, prefer setting a custom event loop policy over redefining the event_loop fixture.

If the pytest.mark.asyncio decorator is applied to a test function, the event_loop fixture will be requested automatically by the test function.

event_loop_policy

Returns the event loop policy used to create asyncio event loops. The default return value is asyncio.get_event_loop_policy().

This fixture can be overridden when a different event loop policy should be used.

Multiple policies can be provided via fixture parameters. The fixture is automatically applied to all pytest-asyncio tests. Therefore, all tests managed by pytest-asyncio are run once for each fixture parameter. The following example runs the test with different event loop policies.

unused_tcp_port

Finds and yields a single unused TCP port on the localhost interface. Useful for binding temporary test servers.

unused_tcp_port_factory

A callable which returns a different unused TCP port each invocation. Useful when several unused TCP ports are required in a test.

def a_test(unused_tcp_port_factory):
    port1, port2 = unused_tcp_port_factory(), unused_tcp_port_factory()
    ...

unused_udp_port and unused_udp_port_factory

Works just like their TCP counterparts but returns unused UDP ports.