Skip to main content
Run your first conformance suite | ESSSynthesize the conformance suite a specification obliges as a TypeScript test package, hold a small implementation to it, and watch it fail when the implementation is wrong.ESSreferenceessreferenceadopterdevelopertry-spec-driven-developmentspecify

Run your first conformance suite

This page holds an implementation to the specification from Write your first specification, in the same tasks directory. It needs Node.js 20 or later.

Synthesize the suite​

The specification obliges a conformance suite: one scenario for each outcome, each lifecycle move and each move that must be refused. ess writes that suite together with a runner, as a Go or a TypeScript test package:

$ ess verify conform synthesize --path . --target typescript --out conformance
note: every declared actor may invoke `tasks.list.AddTask`, so no actor is refused it and no `tasks.list.AddTask/grant/denied` scenario is owed
note: every declared actor may invoke `tasks.list.CompleteTask`, so no actor is refused it and no `tasks.list.CompleteTask/grant/denied` scenario is owed
6 scenario(s) (0 authored), 0 refusal(s), 15 file(s) written to conformance

Implement Target​

The package asks the implementation questions through one interface, Target: run this command, read this view. Write a test file that answers them. The implementation below keeps tasks in a Map; a real target would call your service instead.

conformance/essconform/src/conformance.test.ts
import { test } from "node:test";
import { randomUUID } from "node:crypto";
import { ErrUnsupported, run } from "./index.js";
import type { CommandRequest, CommandResult, Target, ViewRequest, ViewResult } from "./index.js";

type Task = { task_id: string; title: string; priority: unknown; state: "Open" | "Done" };

// An in-memory implementation of the tasks specification. A real target calls your service here.
function newTarget(): Target {
  const tasks = new Map<string, Task>();
  let writes = 0;
  return {
    identity: () => ({ name: "tasks-in-memory", version: "dev" }),
    beginScenario: () => {},
    endScenario: () => {},

    executeCommand(request: CommandRequest): CommandResult {
      const input = request.input;
      // Every answer names the write a read_your_writes read of tasks.list.Tasks is made no older than.
      const consistency = String(++writes);
      switch (request.command) {
        case "tasks.list.AddTask": {
          if (Number(String(input.priority)) < 0) {
            return { outcome: "rejected", error: "tasks.list.InvalidPriority", consistency };
          }
          const task_id = randomUUID();
          tasks.set(task_id, { task_id, title: input.title, priority: input.priority, state: "Open" });
          return {
            outcome: "added",
            consistency,
            directEvents: [
              { event: "tasks.list.TaskAdded", payload: { task_id, title: input.title } },
            ],
          };
        }
        case "tasks.list.CompleteTask": {
          const task = tasks.get(input.task_id);
          if (task === undefined || task.state !== "Open") {
            return { outcome: "already-done", error: "tasks.list.AlreadyDone", consistency };
          }
          task.state = "Done";
          return {
            outcome: "completed",
            consistency,
            directEvents: [
              { event: "tasks.list.TaskCompleted", payload: { task_id: task.task_id } },
            ],
          };
        }
        default:
          throw ErrUnsupported;
      }
    },

    queryView(request: ViewRequest): ViewResult {
      if (request.view !== "tasks.list.Tasks") throw ErrUnsupported;
      const rows = [...tasks.values()].map(({ task_id, title, priority, state }) => ({
        task_id,
        title,
        priority,
        state,
      }));
      return { rows };
    },

    observeEvents: () => [],
    configureExternalOutcome: () => {
      throw ErrUnsupported;
    },
    redeliverEvent: () => {
      throw ErrUnsupported;
    },
    observeInvocations: () => {
      throw ErrUnsupported;
    },
  };
}

await test("conformance", async (t) => {
  await run(t, (): Target => newTarget());
});

tasks.list.Tasks is read_your_writes, so every command answer carries a consistency token, refusals included, and the runner reads the view no older than it; an answer without one fails the view's next check.

Run it​

Install the package's dependencies and run it, asking for a report file. This needs Node.js 20 or later. ESS_REPORT_FORMAT=2 selects the report format this suite requires; without it the runner stops before the first scenario and says so.

$ cd conformance/essconform
$ npm install
…
$ ESS_REPORT_FORMAT=2 ESS_REPORT_OUT=report.json npm test
…
    ok 1 - tasks.list.AddTask/outcome/added
…
    ok 2 - tasks.list.AddTask/outcome/rejected
…
    ok 3 - tasks.list.CompleteTask/outcome/already-done
…
    ok 4 - tasks.list.CompleteTask/outcome/completed
…
    ok 5 - tasks.list.Task/state/Done/refuses/tasks.list.CompleteTask
…
    ok 6 - tasks.list.Task/transition/complete/by/tasks.list.CompleteTask/completed
…
ok 1 - conformance
…
# tasks v1, 6 scenario(s), spec digest ae9ae1d659481748f19a00a1451b0a656fa7abec1474b3c51ff1dc1dd53f0919
# report/2: passed, written to report.json
…

report.json is an ess-conformance-report/2 naming the specification, the implementation, and the count of passed, failed, error, skipped and unsupported scenarios. Its execution_status is passed. Its conformance_status is inconclusive, because this run states nothing about coverage: Verify conformance describes the stricter settings.

Break it​

To see that the suite tests something, break the implementation. Leave the task Open in CompleteTask (task.state = "Open") and run npm test again: three scenarios fail, one of them with step 8: `tasks.list.CompleteTask` took `completed`, and the specification says `already-done` .

Regenerating the package after a change to the specification keeps src/conformance.test.ts, which ess did not write.

Next​