Visual Test

User-invocable skill for visually verifying UI changes using Puppeteer screenshots.

When to use

When you need to visually verify that a UI change looks correct — layout, colors, popover positioning, text content, etc. This runs a real browser against the Zulip test server and takes screenshots that you can read as images.

Steps

1. Write the puppeteer test script

Create web/e2e-tests/_claude_feature_x_test.test.ts using this template:

import type {Page} from "puppeteer";

import * as common from "./lib/common.ts";

async function visual_test(page: Page): Promise<void> {
    await common.log_in(page);
    await common.screenshot(page, "step-1-logged-in");

    // Navigate, interact, and screenshot each significant state.
    // See "Available helpers" below.
}

await common.run_test(visual_test);

Adapt the body to exercise whatever UI you need to verify. Take a screenshot at every visually significant state using descriptive names like step-2-color-picker-open, step-3-color-selected.

2. Run the test

./tools/test-js-with-puppeteer _clause_feature_x_test

This starts a fresh test server on port 9981, runs the script, and saves screenshots to var/puppeteer/.

3. Read the screenshots

Use the Read tool on each var/puppeteer/step-*.png file. Claude's multimodal vision will show the rendered page.

4. Analyze and report

Describe what you see — layout, colors, text content, positioning, any issues. Compare against what was expected.

Zulip displays any JS exceptions encountered as a pop-up, but you should also be able to get them from the puppeteer output.

5. Iterate if needed

If something is wrong, fix the source code (or adjust the test script), then re-run from step 2.

6. Clean up

Once you've gotten a solid test, leave it as an untracked file, so that you can use it when rebasing or iterating on the pull request.

Test infrastructure facts

• •Server URL: http://zulip.zulipdev.com:9981/
• •Login: common.log_in(page) uses credentials from var/puppeteer/test_credentials.json (auto-generated). Default user is Desdemona (realm admin).
• •Known users: common.fullname.cordelia, .othello, .hamlet
• •Screenshots: saved to var/puppeteer/<name>.png
• •Window size: 1400 x 1024
• •Test data: The test database includes a non-system user group hamletcharacters (members: Cordelia, Hamlet).
• •zulip_test global: Only a limited set of internal functions are exposed — see web/src/zulip_test.ts. Functions like get_stream_id and get_user_id_from_name are available, but user_groups is not. Navigate to groups via URL hash routes or by clicking list items instead.

Available helpers (from web/e2e-tests/lib/common.ts)