N8n:testmax Assistant UI

Test an Instance AI feature

Use this skill to test a UI feature of the n8n Assistant end to end. In code, the Assistant is “Instance AI”. You draft the test paths, the user approves them, and the skill runs them all at the same time. A local page shows each run live. At the end, you judge each run and build one report.

The skill uses the scripts of testmax-n8n-ai for the n8n API, the LangSmith usage, the live page server, and the report template. Do not copy those scripts.

What the skill does

flowchart LR
    A[Feature + diff] --> B[Draft scenarios.json<br/>and scripts]
    B --> T[--try and --estimate]
    T --> C{User approves<br/>plan + cost}
    C --> D[run.py]
    D --> E[One fresh branch instance<br/>for each feature + regression]
    D --> F[Fresh branch instance<br/>visual]
    D --> G[Fresh master instance<br/>visual, or a kept run]
    E & F & G --> H[Live page]
    F & G --> I[Pixel + accessibility tree diff]
    E & F & G --> J[summary.txt with triage]
    J --> K[You judge: verdicts.json]
    K --> L[Report rebuilds itself]

• Each run is one scenario: a Playwright script that drives the real Assistant UI in Chrome, with a real LLM.
• There are three kinds of scenario:
  • feature: tests a path of the new feature.
  • regression: tests an existing flow that the feature touches.
  • visual: captures screens. The skill runs it on the branch and on master, then compares the captures.
• All instances are fresh: a new data folder, a new owner, and no workflows or threads. Thus the screens of the branch and master are the same when the code is the same. A fresh instance starts in about 5 seconds, because it copies a data folder that is already migrated and seeded.
• Each feature and regression scenario gets its own fresh instance, so the scenarios do not see each other’s data. The visual scenarios share one branch instance and one master instance.
• The feature flags are the same on all instances. The instances do not ask PostHog for flags, so no instance gets a random experiment variant. Set the flags that the feature needs in the plan, with featureFlags.
• run.py builds this checkout first (with turbo, so a build that is up to date takes about 1 second). The master instance starts from a git worktree at ~/.cache/n8n-feature-test/master, at the merge base of HEAD and origin/master. Thus the visual check shows only the changes of this branch, not the changes that master got after the branch started.
• A master visual run that passed is kept. The next run with the same merge base, the same script and the same flags uses it again, and does not start master.

Requirements

Run python3 .agents/skills/testmax-assistant-ui/scripts/run.py --check before the first run. The commands below use $S for this scripts folder. --check checks the tools, Chrome, the settings, the disk space and the master build, and prints the plan folder for this branch.

• Google Chrome. The scripts use the Playwright package of the repository.
• The Instance AI model settings in .env.local or .env.ai-surfaces, as for your own instance. Fresh instances get the same settings, without the license, the database, the port and the encryption key.
• LANGSMITH_API_KEY and LangSmith tracing, for the tokens and cost. Without them, the report shows no tokens or cost. Do not set N8N_DIAGNOSTICS_ENABLED=false: then Instance AI sends no traces.
• About 3 GB of disk space for the master worktree and its build.

Never put a key on the command line. Read settings from the env files and the environment only.

1. Understand the feature

Find what changed and what the user wants to test:

git diff origin/master...HEAD --stat -- packages/frontend packages/@n8n/instance-ai packages/cli/src/modules/instance-ai
git diff origin/master...HEAD -- <the files of the feature>

Read the changed Vue components, the stores, and the backend events that they use. Find the data-test-id values of the new elements. If the user did not describe the feature, ask for one or two sentences about it.

If the plan has visual scenarios, start the master baseline now, in the background. The first build takes 15 to 20 minutes. Later builds take less than a minute when the turbo cache has the files. You can draft the plan while it builds:

S=.agents/skills/testmax-assistant-ui/scripts
python3 $S/run.py --check         # the setup, and the plan folder
python3 $S/baseline.py prepare    # in the background
python3 $S/baseline.py status     # later: is it ready?

2. Draft the test paths

Write the plan folder that --check prints: ~/.cache/n8n-feature-test/plans/<branch>/<feature>/. The folder stays after a reboot. It holds scenarios.json and one script for each scenario. The folder name is the name of the run folders.

Draft these paths:

• Feature paths. The main path, then each branch of it: other user choices, empty and long inputs, cancel and stop, a reload in the middle, a second thread, errors that the user can see. One path for each scenario.
• Regression paths. The existing flows near the change: a plain chat reply, approvals, the plan review, the preview panel, the thread list. The library has smoke-chat for the plain chat reply.
• Visual screens. The screens that the change can affect, on the branch and on master. Capture each screen in a stable state. Mask all text that comes from the LLM, and all data that changes between runs. The library has visual-assistant-home and visual-thread-reply.

Keep each scenario short and focused. A scenario that fails must show where it failed. Use more scenarios, not longer ones. A visual scenario must not need the new feature, because it also runs on master.

Some UI states show only for a moment, for example a status line that folds away when the run ends. Check them while the run is active, not after it.

If the feature is behind a feature flag or an experiment, set the flag in featureFlags. Without it, the instances use the default value of each flag.

Before you show the plan to the user, check the new scripts and get the estimate (see Check the scripts). Then show the user the list of paths: the id, the kind, the title and the expected result of each. Also show the estimate: the number of LLM runs, the cost and the time. Change the plan until the user approves it.

scenarios.json

{
  "title": "Stop button in the Assistant",
  "feature": "The user can stop a run while the Assistant works.",
  "scenarios": [
    {
      "id": "stop-mid-run",
      "title": "Stop a run in the middle",
      "kind": "feature",
      "script": "stop-mid-run.mjs",
      "expected": "The stop button shows during the run. A click ends the run without an error message.",
      "timeoutMin": 6
    },
    {
      "id": "smoke-chat",
      "title": "A prompt gets a reply",
      "kind": "regression",
      "script": "lib:smoke-chat.mjs",
      "expected": "A short prompt gets the reply OK."
    }
  ]
}

The plan has these fields: title (required), feature (the feature, for the judge), and featureFlags (optional). featureFlags maps a flag name to true, false or a variant name, for example { "<flag name>": "variant" }. Each instance gets these flags, on the branch and on master. They go into N8N_FEATURE_FLAG_OVERRIDES and replace the values in your env files.

Each scenario has these fields:

examples/stop-button/ is a full example plan.

Scenario scripts

A script exports one async function. It gets the kit t:

export default async function (t) {
	await t.step('Open the Assistant', () => t.goto());
	await t.step('Send a prompt', () => t.send('Reply with exactly the word OK and nothing else.'));
	await t.step('Wait until the run ends', () => t.waitForIdle({ timeout: 180_000 }));
	await t.check('The reply says OK', () => t.expect(t.ai.assistantMessages().last()).toContainText('OK'));
	await t.capture('thread', { mask: [t.ai.assistantMessages()] });
}

Rules for scripts:

• Use data-test-id locators (page.getByTestId). Use text only for text that the test controls.
• Use t.expect(...).toBeVisible() and other assertions that wait. Do not use t.sleep to wait for the UI.
• LLM answers change from run to run. Check the UI state, not the exact words. Ask for a fixed reply, such as “Reply with exactly the word OK”, when you need a known answer.
• To test an approval, set "autoConfirm": false, wait with t.waitForIdle() until it returns 'suspended', then click the button.

Check the scripts

Check the new scripts on fresh instances before you show the plan:

python3 $S/run.py --plan <plan>/scenarios.json --try --only id1,id2

--try does not run master, does not start the live page, and builds no report. It prints a table with the status, the steps and the first error of each run. The runs are in /tmp/feature-test/try/. Fix the scripts that fail because of the script, then try them again. Each LLM scenario in a try costs money too, so try only the new scripts.

Then get the estimate for the full run:

python3 $S/run.py --plan <plan>/scenarios.json --estimate

The estimate uses the cost and time of earlier runs of the same scenario ids. A scenario without an earlier run shows * and the median of all earlier runs. A master run that is kept shows (kept) and costs nothing.

3. Run

Open the live page for the user on each run. Do not skip this step. Do this:

1. Find out if your harness has a browser tool that opens a tab in the editor. In Cursor, this is browser_navigate of the cursor-ide-browser MCP server.

2. If it has one, start the run in the background with --no-open:

   bashCopy

   python3 $S/run.py --plan <plan>/scenarios.json --no-open

   Wait for the live page: <url> line in the output, which comes in a few seconds. Then open that URL in a new editor tab that the user can see (in Cursor: newTab: true and position: "active"). If the tab does not open, run open <url> (macOS) or xdg-open <url> (Linux).

3. If it has none, start the run in the background without --no-open. run.py opens the live page in the default browser:

   bashCopy

   python3 $S/run.py --plan <plan>/scenarios.json

4. Give the user the URL in both cases.

run.py does not read $BROWSER, so do not set it.

run.py does these steps:

1. Prints the estimate and checks the setup. It stops when the setup has an error, for example a missing Chrome.
2. Copies the plan into a new run folder, /tmp/feature-test/<time>-<plan folder name>/.
3. Starts the live page and prints its URL. Without --no-open, it opens the page in the default browser.
4. Builds this checkout with turbo. A build error stops the run, and the output shows the end of build.log.
5. Starts the instances: one for each feature and regression scenario, one branch instance for the visual scenarios, and one master instance. It starts the instances ahead of their scenario. Master starts only for the master runs that it does not keep from an earlier run. It prepares the master build first, if it is not ready.
6. Runs the scenarios, 4 at a time. Each run records a video, the steps with screenshots, the browser errors, the thread events, and the LangSmith ids.
7. Stops the instances, compares the visual captures, writes summary.txt, and builds the report without verdicts.
8. Prints a result table, the command to run the plan again, and one JSON object on several lines: runDir, report, live, summary, results (the status of each run), visual (the number of captures, the changed ones, and the error when the visual comparison failed), rerun and next.
9. Gets the tokens and cost from LangSmith, then builds the report again. LangSmith receives traces with a delay, so this can take up to 90 seconds. You can start to judge while it runs.

Watch the runs

The live page shows each run as a row, with its status and its last screenshot. The screenshot changes every few seconds. When the run is done, the same address shows the report. The page stops 30 minutes after its last request.

4. Judge

Read <runDir>/summary.txt. It starts with a triage: each run is clean, or look closer with the reasons (a failed step or check, a browser error, a failed tool call, or a visual change). Then it has, for each run: the expected result, the steps and their status with the path of each screenshot, the prompts, the last reply, the browser errors, and the visual results.

For a clean run, look at the last screenshot and check it against the expected result. For a run to look at closer, look at the screenshots of the steps in the reasons, and the diff images in visual/<id>/.

A script that passed is not always a pass. Check that the run shows the expected result, not only that the script ended. Check for these problems:

• a browser error or a failed request that comes from the feature
• a step that passed, but the screenshot shows the wrong state
• a visual change that the feature did not intend
• a script that failed because of the script, not the feature. Say so, and fix the script

Write <runDir>/verdicts.json. Use the run names as keys. A master run has the name <id>--master, and does not need a verdict:

{
  "stop-mid-run": {
    "verdict": "pass",
    "summary": "One sentence about the result.",
    "checks": [
      { "ok": true, "text": "The stop button ends the run" },
      { "ok": false, "text": "The send button comes back after 9 seconds" },
      { "ok": null, "text": "Could not confirm the stopped label" }
    ]
  }
}

Use pass when all checks pass, fail when the main goal is not met, and partial for all other results. For a visual scenario, judge each change: intended by the feature, a regression, or noise (for example, a timestamp that is not masked). Be strict and factual.

Write each check as one short sentence with one fact. Put selectors, test IDs and UI text in backticks. The page shows them as code. The page shows the failed checks first.

5. The report

While the live page runs, it builds the report again each time verdicts.json changes. The open tab loads the new report by itself, and keeps the selected run and the scroll position. Thus you do not need to load the page again. When the live page does not run, build the report yourself:

python3 $S/report.py <runDir>

The report is <runDir>/report/index.html. It is one folder with all its files, so you can copy or share it. It has, from top to bottom:

• the video replays of all runs
• a table of all runs: kind, result, steps passed, time, LLM calls, tool calls, tokens, cost and browser errors. The result is your verdict. A master run shows Baseline, and a run without a verdict shows Not judged, or Failed when its script failed
• the visual check: the branch screen, the master screen, and the diff image of each capture, with the accessibility tree diff
• for each run: the video of the run, the expected result and the verdict, the steps with their screenshots, the browser errors, and the LLM steps from the trace. A click on a row of the table shows the panel and the video of that run, and pauses the video of the other runs

Each box shows closed. It opens and closes when you click its title. On the live page, a box that you open or close stays that way when the page updates.

A master run that is kept from an earlier run shows “Reused” in its run box.

Give the user the path and the live URL. Tell the user the result of each scenario, the visual changes, and the problems that you found.

Single steps

Limits

• LLM answers change from run to run, and a run can fail because of the LLM. Run a failed scenario again with --rerun last --only <id> before you call it a bug.
• A stopped LLM call does not show in LangSmith. The cost of a run with a stop includes only the calls that ended.
• Each LLM scenario costs money. The tokens and cost show in the report.
• Parallel runs share the CPU and the LLM rate limits. The times include the shared load.
• The visual check compares pixels with a small tolerance. Fonts and animations can cause small changes. Masks hide the parts that change between runs. The accessibility tree diff shows changes in structure and text.
• The worktree shows in git worktree list. To remove it, run git worktree remove ~/.cache/n8n-feature-test/master.
• Kept master runs older than 14 days are deleted. The instance data templates in ~/.cache/n8n-feature-test/templates change when the migrations change. You can delete old templates at any time.
• A run folder is about 35 MB. The run folders are in /tmp, so the system deletes them on reboot.