6. Prove it in the testlab

Declare a test block and let the three-run protocol prove convergence in a disposable instance.

Before you start: Write your own package

A test block in package.wcl names an image and one or more static steps (no variable references). config-weave test boots a disposable instance — a docker container by default, a vmlab VM when the test needs a real machine — copies the binary and a synthesized playbook in, and runs the three-run protocol: check (must report not configured), apply (must converge), apply again in a fresh process (must change nothing).

Run 2 catches resources that don't converge; run 3 catches the subtler bug — state that only looks converged to the process that created it. Filter with pkg or pkg:test, and keep a failing instance alive with --keep to shell in and inspect.

§ 1Exercise: Test your package end-to-end

Add a test for your dir_present resource and run it in a docker instance.

// in pkgs/mypkg/package.wcl
test "dir_present_converges" {
  description = "dir_present creates the directory and is idempotent"
  image = "debian:12"
  step "make-dir" {
    description = "Create a work directory"
    resource   = "dir_present"
    properties { path = "/var/tmp/weave-test" }
  }
}

§ 2Exercise: Watch the protocol catch a bug

Make apply() create the state somewhere check() doesn't look (e.g. append a suffix to the path), re-run the test, and read which run fails.

config-weave test ./my-playbook mypkg:dir_present_converges --keep