cypress-tap

Files (7)

• SKILL.md
• json-recipes.md · references/
• reading-results.md · references/
• reading-the-app.md · references/
• recipes.md · references/
• session-lifecycle.md · references/
• troubleshooting.md · references/

SKILL.md (first lines)

# Driving Cypress with `cypress tap`

`cypress tap` controls an already-running `cypress open` session. Use it to iterate on specs,
inspect the reporter and command log, and read the app under test without GUI interaction.
Use `cypress run` instead for a one-shot headless batch.

## Core loop

```bash
npx cypress tap sessions                    # confirm a session; note pid if several exist
npx cypress tap status                      # baseline startedAt + spec
npx cypress tap run cypress/e2e/foo.cy.ts   # async — returns immediately
# poll status until passed|failed for your spec with a changed startedAt
npx cypress tap reporter
npx cypress tap reporter --test-id r3       # one test: log, network, stubs, error
```

`run` is asynchronous. A stale verdict matches a fresh one on every field except `startedAt`,
and a watcher rerun of the **selected** spec can advance `startedAt` without running your file.
Gate on `startedAt`, `spec`, and a terminal status. Do not wait to observe `running` — fast
specs can finish between polls. Copy-paste poller:
[session-lifecycle.md](references/session-lifecycle.md). JSON field helpers:
[json-recipes.md](references/json-recipes.md).

In poll loops, prefer `./node_modules/.bin/cypress tap …` over `npx cypress tap …` when the
project pins Cypress.

## Prerequisites

- Confirm from package metadata or the lockfile that the resolved Cypress is 15.21.0+ and
  contains `tap`. Do not use `tap --help` to probe an unknown older build; prereleases below the
  version floor may attempt session discovery instead of printing help.
- The session must use Electron, Chrome, Chromium, or Edge. Firefox and WebKit are unsupported.
- `cypress open` and any configured `baseUrl` dev server must already be running.
- The cwd chooses both the Cypress binary and the automatically selected session. When the
  target project pins an older Cypress, run `tap` from a compatible checkout and pass
  `--session <pid>` on every call.

## Route by task

- **Start, select, or poll a session:** read
  [session-lifecycle.md](references/session-lifecycle.md).
- **Run a spec or read its results:** read [session-lifecycle.md](references/session-lifecycle.md)
  and [reading-results.md](references/reading-results.md).
- **Author or inspect a spec:** read [recipes.md](references/recipes.md) and
  [reading-the-app.md](references/reading-the-app.md).
- **Diagnose a failure:** read [recipes.md](references/recipes.md),
  [reading-results.md](references/reading-results.md), and
  [reading-the-app.md](references/reading-the-app.md).
- **Command failure, hang, wrong project, or surprising output:** read
  [troubleshooting.md](references/troubleshooting.md).
- **Parse `--json` or script a poll:** read [json-recipes.md](references/json-recipes.md).
- **One noninteractive batch:** use `cypress run`, not `tap`.

Read only the references required for the current task.

## Core commands

- `sessions`: reachable sessions, project roots, testing types, and browsers; JSON adds support
  and renderer health.
- `status`: lifecycle stage, selected spec, run identity, counts, build error, and active pin.
- `specs`: runnable project-relative spec paths for the session's testing type.
- `run <spec>`: dispatches a spec and returns immediately.
- `reporter`: spec overview and test ids; with `--test-id`, the complete test attempt.
- `command`: one command-log row with network data, snapshots, and console properties.
- `pin`: rewinds the app frame to a command snapshot.
- `dom`, `aria`, `inspect`: read the settled app or currently pinned snapshot.

All commands accept `--session <pid>`, `--json`, and `--timeout <ms>`. On a confirmed supported
build, use `npx cypress tap <command> --help` for command-specific flags. Help is generated from
the live session contract — when help and this skill disagree, trust help.

## The non-negotiable verdict rule

`run` confirms dispatch, not execution, and returns before the new run starts. During that gap,
`status` and app reads can still return the previous run's plausible verdict and page.

For every explicit run:

1. Read the current `startedAt`.
2. Dispatch exactly one spec.
3. Poll one `status --json` response at a time.
4. Accept only `passed` or `failed` for the expected `spec` with a non-empty, changed
   `startedAt`. `startedAt` is null only when no run has ever started for that spec in the
   session — a build failure on first selection. A build that fails on rerun or on a watcher
   rebuild still advances `startedAt`, so it takes the normal path. Keep the null fallback
   (a changed observable baseline, or a preceding `loading`/`running` observation) for the
   first-selection case only.
5. Bound the loop and fail if no matching fresh verdict arrives.

Saving the active spec triggers an automatic watcher run. After editing, either use that run or
let it settle before taking a baseline and dispatching another. Never intentionally put two runs
in flight.

Blank and partial payloads from a successful `status` call occur transiently. Treat missing
fields as "keep waiting," not as a state change. A nonzero `status` exit is a command failure,
not a partial read: stop polling and report it.

Only `passed` and `failed` are verdicts. A build failure is `failed` with the diagnostic in
`status.error`, possibly before any tests exist. `status` is the only surface that carries that
diagnostic — `reporter` renders a failed build as an empty spec.

## Critical correctness rules

1. **Target the intended session.** If several sessions exist, or auto-selection behaves oddly,
   inspect `sessions` and pass `--session <pid>` on every call. Auto-selection can choose another
   project or an unresponsive session. E2e and component testing use separate sessions: they can
   share a `projectRoot` but expose different `specs` lists, and only `status` names which
   session answered — other commands carry no pid in their output.
2. **Preserve the binary location.** Cwd controls `npx` resolution on every call. When the
   project pins an older Cypress, run commands from a compatible checkout and pass
   `--session <pid>`.
3. **Do not parse failed commands.** Check the exit code before parsing JSON. Supported-build
   failures generally use stderr, but older compatibility failures may use stdout. An ambiguous
   selector is the intentional exception: it exits `1` and lists matches on stdout.
4. **Do not discard dispatch stdout while checking compatibility.** An older Cypress may print
   `Unknown command "tap"` and usage text to stdout; redirecting it hides the cause.
5. **Redirect potentially large JSON.** `reporter --test-id --json` and `command --json` can be
   hundreds of kilobytes. Save them to a file and parse the file.

From cypress-io/ai-toolkit, MIT.

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