agentcat_sdk/

testing.rs

//! [`Fake`]: a test double that records what a tracked server publishes, so a customer's test can
//! assert on it. Enable the `test-util` feature of the crate to use it.

use std::fmt;
use std::sync::{Arc, Mutex, PoisonError};
use std::time::Duration;

use crate::AgentCat;
use crate::config::Options;
use crate::delivery::Observer;
use crate::event::Event;
use crate::pipeline::EventObject;

/// The event type of a tool call.
const TOOL_CALL: &str = "mcp:tools/call";
/// The event type of a custom event.
const CUSTOM: &str = "agentcat:custom";
/// How long [`Fake::events`] waits for each handle to deliver.
const FLUSH: Duration = Duration::from_secs(5);

/// The events that finished the pipeline of the handles of one [`Fake`], in that order.
#[derive(Debug, Default)]
struct Recorder {
    events: Mutex<Vec<Event>>,
}

impl Observer for Recorder {
    fn finished(&self, event: &EventObject) {
        self.events
            .lock()
            .unwrap_or_else(PoisonError::into_inner)
            .push(Event::from_object(event));
    }
}

/// A test double for `AgentCat`: it builds handles whose events never leave the process and
/// records every event that finishes the pipeline, telemetry-only events (an empty project ID)
/// included. The `identify`, tag, property and `redact_event` hooks run as they do in production,
/// so a recorded event is the one that would have been published.
///
/// A `Fake` is an instance, not a global: two fakes in one process see only their own handles.
/// Clones share the record. Its handles are always on (they ignore `AGENTCAT_ENABLED`), never
/// configure the process logger and use a publisher that never sends, so a test needs no network.
/// The log destination is process-wide and the first handle that configures it decides it, so the
/// handles of a fake write no `~/agentcat.log` lines unless a handle built with [`AgentCat::new`]
/// or [`AgentCat::from_env`] in the same process configured it: then their lines go there too.
///
/// A fake keeps a clone of each handle it built, so the last clone drops with the fake and the
/// servers that hold one, and that drop drains as any handle does (see [dropping the last
/// handle](AgentCat#dropping-the-last-handle)): for up to 5 s, and under `#[tokio::test]`, a
/// current-thread runtime, an event that still needs a hook is dropped after that wait. The
/// assertion methods flush first, so after them the drop has nothing left to wait for, unless a
/// flush timed out: the events that flush left wait for the drop.
///
/// ```
/// # async fn run() {
/// use agentcat_sdk::Options;
/// use agentcat_sdk::testing::Fake;
///
/// # struct MyServer;
/// # impl rmcp::ServerHandler for MyServer {}
/// let fake = Fake::new();
/// let server = fake.agentcat("proj_123", Options::default()).track(MyServer);
/// // ... serve `server` and make calls against it ...
/// # let _ = server;
/// fake.assert_nothing_tracked().await;
/// # }
/// ```
///
/// The assertion methods panic with a message that lists the recorded events' types and
/// resource names, and says so when a handle did not finish delivering within the 5 s flush (a
/// hook slower than that holds its event back).
#[derive(Clone, Debug, Default)]
pub struct Fake {
    recorder: Arc<Recorder>,
    handles: Arc<Mutex<Vec<AgentCat>>>,
}

impl Fake {
    /// A fake with no handles and no events.
    pub fn new() -> Self {
        Self::default()
    }

    /// A handle for `project_id` (empty means telemetry only) whose events this fake records and
    /// whose publisher never sends. Wrap a server with [`AgentCat::track`].
    pub fn agentcat(&self, project_id: impl Into<String>, options: Options) -> AgentCat {
        let handle = AgentCat::offline_observed(
            project_id.into(),
            options,
            Arc::clone(&self.recorder) as Arc<dyn Observer>,
        );
        self.handles
            .lock()
            .unwrap_or_else(PoisonError::into_inner)
            .push(handle.clone());
        handle
    }

    /// Flushes every handle this fake built, for up to 5 s each, then returns the recorded events
    /// in the order they finished. An event whose hooks take longer than that is not among them.
    pub async fn events(&self) -> Vec<Event> {
        self.recorded().await.events
    }

    /// [`Fake::events`], and whether every handle finished delivering within [`FLUSH`].
    async fn recorded(&self) -> Recorded {
        let handles: Vec<AgentCat> = self
            .handles
            .lock()
            .unwrap_or_else(PoisonError::into_inner)
            .clone();
        let mut settled = true;
        for handle in handles {
            settled &= handle.flush(FLUSH).await;
        }
        let events = self
            .recorder
            .events
            .lock()
            .unwrap_or_else(PoisonError::into_inner)
            .clone();
        Recorded { events, settled }
    }

    /// Asserts that a tool call of the tool `tool_name` was tracked.
    ///
    /// # Panics
    ///
    /// When no recorded tool-call event has that resource name.
    pub async fn assert_tracked(&self, tool_name: &str) {
        let recorded = self.recorded().await;
        let found = recorded
            .events
            .iter()
            .any(|e| e.event_type == TOOL_CALL && e.resource_name.as_deref() == Some(tool_name));
        assert!(
            found,
            "expected a tracked call of tool `{tool_name}`, {recorded}"
        );
    }

    /// Asserts that exactly `count` tool calls were tracked (custom events do not count).
    ///
    /// # Panics
    ///
    /// When the number of recorded tool-call events differs.
    pub async fn assert_tracked_count(&self, count: usize) {
        let recorded = self.recorded().await;
        let actual = recorded
            .events
            .iter()
            .filter(|e| e.event_type == TOOL_CALL)
            .count();
        assert!(
            actual == count,
            "expected {count} tracked tool calls, found {actual}, {recorded}"
        );
    }

    /// Asserts that no event of any kind was recorded.
    ///
    /// # Panics
    ///
    /// When any event was recorded.
    pub async fn assert_nothing_tracked(&self) {
        let recorded = self.recorded().await;
        assert!(
            recorded.events.is_empty(),
            "expected nothing was tracked, {recorded}"
        );
    }

    /// Asserts that a custom event with the resource name `resource_name` was published.
    ///
    /// # Panics
    ///
    /// When no recorded custom event has that resource name.
    pub async fn assert_custom_event_published(&self, resource_name: &str) {
        let recorded = self.recorded().await;
        let found = recorded
            .events
            .iter()
            .any(|e| e.event_type == CUSTOM && e.resource_name.as_deref() == Some(resource_name));
        assert!(
            found,
            "expected a custom event `{resource_name}`, {recorded}"
        );
    }
}

/// What an assertion of a [`Fake`] saw: the recorded events and whether every handle finished
/// delivering within [`FLUSH`].
struct Recorded {
    events: Vec<Event>,
    settled: bool,
}

impl fmt::Display for Recorded {
    /// The types and resource names of the events, such as `recorded: [mcp:tools/call echo,
    /// agentcat:custom x]`, then a note when a flush timed out.
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.write_str("recorded: [")?;
        for (i, e) in self.events.iter().enumerate() {
            if i > 0 {
                f.write_str(", ")?;
            }
            write!(
                f,
                "{} {}",
                e.event_type,
                e.resource_name.as_deref().unwrap_or("-")
            )?;
        }
        f.write_str("]")?;
        if !self.settled {
            write!(
                f,
                " (a handle did not finish delivering within the {} s flush: an event whose hooks \
                 take longer is not recorded yet)",
                FLUSH.as_secs()
            )?;
        }
        Ok(())
    }
}

#[cfg(test)]
mod tests;