tracing integration

Cucumber::init_tracing() (enabled by tracing feature in Cargo.toml) initializes global tracing::Subscriber that intercepts all the tracing events and transforms them into event::Scenario::Logs. Each Writer can handle those event::Scenario::Logs in its own way. writer::Basic, for example, emits all the event::Scenario::Logs only whenever scenario itself is outputted.

extern crate cucumber; extern crate tokio; extern crate tracing;  use std::{ sync::atomic::{AtomicUsize, Ordering}, time::Duration, }; use cucumber::{World as _, given, then, when}; use tokio::time; #[derive(Debug, Default, cucumber::World)] struct World; #[given(regex = r"(\d+) secs?")] #[when(regex = r"(\d+) secs?")] #[then(regex = r"(\d+) secs?")] async fn sleep(_: &mut World, secs: u64) { static ID: AtomicUsize = AtomicUsize::new(0); let id = ID.fetch_add(1, Ordering::Relaxed); tracing::info!("before {secs}s sleep: {id}"); time::sleep(Duration::from_secs(secs)).await; tracing::info!("after {secs}s sleep: {id}"); } #[tokio::main] async fn main() { World::cucumber() .init_tracing() .run("tests/features/wait") .await; }

Loosing tracing::Span

tracing::Span is used to wire emitted tracing events (logs) to concrete scenarios: each scenario is executed in its own tracing::Span. In case a tracing event is emitted outside the tracing::Span of a scenario, it will be propagated to every running scenario at the moment.

extern crate cucumber; extern crate tokio; extern crate tracing;  use std::{  sync::atomic::{AtomicUsize, Ordering},  time::Duration, };  use cucumber::{World as _, given, then, when}; use tokio::time;  #[derive(Debug, Default, cucumber::World)] struct World;  #[given(regex = r"(\d+) secs?")] #[when(regex = r"(\d+) secs?")] #[then(regex = r"(\d+) secs?")] async fn sleep(_: &mut World, secs: u64) {  static ID: AtomicUsize = AtomicUsize::new(0);   let id = ID.fetch_add(1, Ordering::Relaxed);   tracing::info!("before {secs}s sleep: {id}");  time::sleep(Duration::from_secs(secs)).await;  tracing::info!("after {secs}s sleep: {id}"); }  #[tokio::main] async fn main() { // Background task outside of any scenario. tokio::spawn(async { let mut id = 0; loop { time::sleep(Duration::from_secs(3)).await; tracing::info!("Background: {id}"); id += 1; } }); World::cucumber() .init_tracing() .run("tests/features/wait") .await; }

As we see, Background: 2/3/4 is shown in multiple scenarios, while being emitted only once each.

TIP: If you're spawning a Future inside your step matching function, consider to propagate its tracing::Span into the spawned Future for outputting its logs properly.