Testing

cargo-athena gives you a fast inner loop without a cluster, plus guard rails before code reaches one. Four levels, fastest to most thorough.

1. Unit-test the container body

A #[container] body is ordinary Rust, so call it from a regular #[test]:

#[container]
fn summarize(data: String, top_n: i64) -> String {
    format!("top-{top_n}:{data}")
}

#[test]
fn summarize_picks_top_n() {
    assert_eq!(summarize("hello".into(), 3), "top-3:hello");
}

No harness, no infrastructure. This is the right test for “does my business logic do the right thing on these inputs?”.

2. Run the step like Argo would (emulate)

For “does the step run correctly in its container?”, cargo athena emulate is the fast inner loop. It runs one #[container] under docker or podman with the same image, the same injected bootstrap, the same parameter env, the /athena scratch dir, host! binds, and S3 artifact ports.

cargo athena emulate ./my-workflow -w transform -a data=hi -a factor=2

By default it pulls the deployed binary from S3, so what you emulate is what’s actually live. --build packages a fresh local musl binary instead; --tarball F uses one verbatim.

Arguments are type-checked against the real function signature before anything launches, so wrong types fail fast with a clear message instead of a serde panic inside the pod.

Not emulated: anything Kubernetes-specific (ServiceAccount, RBAC, nodeSelector, podSpecPatch). See the CLI page for the full list and flags.

3. Snapshot the emitted YAML

cargo athena emit is deterministic, so snapshot it and fail CI on unintended changes:

# Commit a baseline
cargo athena emit --package my-workflows > tests/golden/emit.yaml

# In CI, fail loud on any diff
diff <(cargo athena emit --package my-workflows) tests/golden/emit.yaml

This catches DAG / wiring / parameter regressions before a cluster ever sees them. cargo-athena’s own test suite does this across a broad “all features” fixture (see examples/smoke/tests/golden/) plus trybuild compile-fail tests pinning the strict body grammar and macro guards.

4. End-to-end on real Argo

For full conformance, submit to a real Argo + S3:

cargo athena publish
cargo athena submit my-crate-pipeline -a seed=hi

Wait for the run, assert it Succeeded. The project’s own GitHub Actions matrix does exactly this on every push to main against three Argo versions (4.0.5 / 3.7.14 / 3.6.19) and the badges in Supported Argo Versions are that live result.

To reproduce the cluster locally:

scripts/deploy.sh && scripts/e2e-test.sh && scripts/teardown.sh

You need a Docker or Podman daemon. nix develop provides kind / argo / mc if you use Nix.