n8n/packages/testing/playwright/docs/ORCHESTRATION.md

Custom Test Orchestration

Capability-aware test distribution across CI shards.

How It Works

Step	What Happens
1. Discovery	pnpm janitor discover (AST-based, detects test.fixme()/test.skip() automatically)
2. Metrics	Get avgDuration per spec from Currents (last 7 days)
3. Default	Missing specs get 60s default (accounts for container startup)
4. Group	Group specs by @capability:xxx tag for worker reuse
5. Effective Duration	Calculate actual time accounting for container reuse within groups
6. Split	If a group exceeds 5 min, split into sub-groups
7. Limit	Aim for 5 min of tests on each shard, one shard per capability
8. Bin Pack	Greedy assign groups + standard specs to lightest shard

Why Group by Capability?

Tests requiring containers (proxy, email, etc.) include ~20s startup overhead. When grouped on the same shard, only the first test pays this cost - the rest reuse the worker.

Example: 15 proxy tests across 8 shards = 8 container starts (160s). Grouped on 2 shards = 2 starts (40s). Saves 120s.

Why the Shard Count Has a Limit

Each shard pays about 3.4 minutes of fixed setup: checkout, Setup Environment, browser install, and image load. This cost does not change with the size of the workload. An impact-scoped PR selects only a few specs. Without a limit, the packer distributes those few minutes of tests over many runners, and each runner pays the full setup cost.

targetShardDuration (5 minutes) limits the bucket count to ceil(totalTestTime / targetShardDuration). The packer creates only the shards it can fill. minShardSpecs applies a second limit to the same count. Set it to 1 to disable it.

The name says target, not minimum, because ceil divides the work evenly over the shards that remain. A 12-minute selection gets 3 shards of 4 minutes, not 2 shards of 6 minutes. floor would enforce a true minimum, but it would also add about 2 minutes of wall-clock time to keep one more runner idle.

The shard count never drops below the number of capability groups. One runner that starts every image set pays back in container startup what it saved in setup. Capability groups therefore stay on separate shards.

The packer applies the limits before it fills the buckets. Bin-packing still balances the shards. This is not a merge step after the packer runs.

Full-suite selections do not change: about 196 minutes of test time still fills all 16 shards. Over 7 days of PR CI, the limit removed about 9% of the E2E shard jobs, and the average wall-clock time did not increase.

Configure both values under orchestration in janitor.config.mjs.

Self-Balancing

Metrics auto-correct over time. As grouped tests run, they report actual execution time (not startup overhead), so future distributions become more accurate.

Writing Tests with Capabilities

1. Use capability option (enables worker reuse)

// String capability - maps to predefined config
test.use({ capability: 'proxy' });

// Custom config - full control over container settings
test.use({
  capability: {
    proxyServerEnabled: true,
    env: { MY_VAR: 'value' },
  },
});

2. Add @capability tag (required for orchestration grouping)

test('My feature @capability:proxy', async ({ page }) => {
  // This test will be grouped with other proxy tests
});

// Or at describe level:
test.describe('Feature @capability:email', () => {
  // All tests inherit the tag
});

Available Capabilities

Capability	Tag	Containers
'proxy'	@capability:proxy	Proxy server
'email'	@capability:email	Mailpit
'source-control'	@capability:source-control	Git server
'task-runner'	@capability:task-runner	Task runner
'oidc'	@capability:oidc	OIDC provider
'observability'	@capability:observability	VictoriaLogs + VictoriaMetrics + Vector

Modes vs Capabilities

Capabilities (@capability:X) are add-on features you can combine with any infrastructure:

• Use test.use({ capability: 'proxy' }) to configure the worker
• Add-on containers (proxy, email, gitea, etc.) spin up alongside n8n

Modes (@mode:X) define the infrastructure configuration itself:

• @mode:postgres - n8n with PostgreSQL database (vs default sqlite)
• @mode:queue - n8n with EXECUTIONS_MODE=queue (workers via Bull, rarely used as tag)
• @mode:multi-main - n8n HA setup with leader election (implies queue mode)

Most e2e tests run against ALL modes via projects (sqlite:e2e, postgres:e2e, etc). Use @mode:X only for tests that ONLY work with a specific infrastructure.

// Capability - add-on feature
test.use({ capability: 'proxy' });
test('API mocking @capability:proxy', ...);

// Mode - infrastructure requirement (no test.use needed, project handles it)
test('Postgres-specific test @mode:postgres', ...);

// Combined - capability ON a specific mode
test.use({ capability: 'observability' });
test('Multi-main logs @capability:observability @mode:multi-main', ...);

Both @capability:X and @mode:X tests are skipped in local mode (they require containers).

Temporarily Disabling Tests

Use test.fixme() to mark tests that need fixing. The janitor's discover command detects test.fixme() and test.skip() calls via AST analysis and automatically excludes them from CI distribution.

// Individual test
test.fixme('broken test', async ({ n8n }) => {
  // Excluded from CI distribution automatically
});

// Entire describe block
test.describe('Feature', () => {
  test.fixme(); // Marks all tests in this block

  test('test 1', async ({ n8n }) => { ... });
  test('test 2', async ({ n8n }) => { ... });
});

Attempt-Aware Retry Filtering

When a shard fails in CI and the user clicks Re-run failed jobs, GitHub re-runs the full shard manifest. janitor filter-shard shrinks that to just the specs that failed in the previous attempt.

echo "$MATRIX_SPECS" | janitor filter-shard

• Reads candidate spec paths from stdin (newline- or space-separated)
• On GITHUB_RUN_ATTEMPT == 1: passes candidates through unchanged
• On GITHUB_RUN_ATTEMPT > 1: POSTs { runId, previousAttempt, candidates } to the coordinator webhook (default https://internal.users.n8n.cloud/webhook/failed-specs, override with --url=<...> or JANITOR_FILTER_SHARD_URL), prints the intersection
• Fails open on any error (timeout, non-2xx, parse error, fallback response) — emits the original candidate list so a coordinator outage never breaks CI
• Wired into test-e2e-reusable.yml between "Pre-pull Test Container Images" and "Run Tests"; the coordinator (an n8n workflow) holds the Currents API key server-side, so fork PRs get the same benefit without exposing secrets

Refreshing Metrics

CURRENTS_API_KEY=<key> node packages/testing/playwright/scripts/fetch-currents-metrics.mjs --project=nHHLA5

This fetches the last 7 days of test durations from Currents, aggregates by spec, and writes to .github/test-metrics/playwright.json. The PR-CI project is nHHLA5 (n8n-ci); the legacy LRxcNt project still backs the nightly e2e workflows.

When to refresh:

• Weekly (recommended)
• After significant test changes
• When adding new specs (optional - they get 60s default)

Stale metrics do not cause an obvious failure. The packer still reports balanced shards, because it balances against the durations in the file. The real spread is what changes. A 3-month-stale file predicted a uniform 9.7 minutes for each shard. Against refreshed durations, the same shards took 8.6 to 18.5 minutes.

How to read the reported numbers: Currents avgDuration is about 1.5 times the test time that a shard uses in CI. Use Total test time and Expected wall-clock to compare the shards with each other. Do not use them as absolute predictions. targetShardDuration uses these same units.

Architecture

janitor orchestrate (generic)          distribute-tests.mjs (n8n CI adapter)
┌──────────────────────────┐          ┌──────────────────────────┐
│ AST discovery            │          │ Calls janitor orchestrate│
│ Metrics loading          │   JSON   │ Maps capabilities →      │
│ Capability grouping      │ ──────→  │   Docker images          │
│ Group splitting          │          │ Adds container overhead  │
│ Greedy bin-packing       │          │ Outputs GH Actions matrix│
└──────────────────────────┘          └──────────────────────────┘

The janitor handles generic orchestration (works for any Playwright project). distribute-tests.mjs is n8n's CI adapter that maps capabilities to Docker images.

Scripts

Script	Purpose
scripts/distribute-tests.mjs	CI adapter — calls janitor, maps images, outputs matrix
scripts/fetch-currents-metrics.mjs	Fetches metrics from Currents API

Testing Locally

# Janitor orchestration (generic output)
pnpm janitor orchestrate --shards=14

# CI adapter (n8n-specific output with Docker images)
node scripts/distribute-tests.mjs --matrix 14 --orchestrate

# Get specs for shard 0
node scripts/distribute-tests.mjs 14 0

Troubleshooting

Problem	Solution
Specs not running	Check path matches janitor test patterns in janitor.config.mjs
Unbalanced shards	Refresh metrics - durations may have drifted
Worker not reused	Use string capabilities like 'proxy', not inline objects