What is writing-e2e-tests?

A guide for adding end-to-end tests to Opik, meaning tests that exercise a feature through the application as a user would. It uses Playwright, a browser-testing tool, together with page objects, test data, and SDK clients.

Writing browser tests for Opik features such as dataset flows, experiment comparisons, trace exploration, and online evaluation. It explains where to put test files, page models, fixtures, and data-seeding code.

It provides a consistent way to test complete user flows instead of checking isolated functions. The supporting fixtures and clients make it easier to create test data and clean it up afterward.

writing-e2e-tests — Skill for Claude Code and Codex by comet-ml: A guide for adding end-to-end tests to Opik, meaning…

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods

npx agentmods add skills/comet-ml/opik/writing-e2e-tests

Any agent

npx skills add comet-ml/opik --skill writing-e2e-tests

Clone the repo

git clone --depth 1 https://github.com/comet-ml/opik

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/skills/comet-ml/opik/writing-e2e-tests.svg)](https://agentmods.dev/skills/comet-ml/opik/writing-e2e-tests)

Your own site

<a href="https://agentmods.dev/skills/comet-ml/opik/writing-e2e-tests"><img src="https://agentmods.dev/badge/skills/comet-ml/opik/writing-e2e-tests.svg" alt="Measured on agentmods" height="20"></a>

Per session 126 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 2,863 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. Scan, not verified.

Origin original No closer match found in the catalogue.

Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

Model	Per session	Once invoked
Fable 5	$0.00126	$0.02863
Opus 5	$0.00063	$0.01432
Sonnet 5	$0.00025	$0.00573
Haiku 4.5	$0.00013	$0.00286

Measured 4d ago against content hash 281cba0ff01f, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

writing-e2e-tests scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 4d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.agents/skills/writing-e2e-tests/SKILL.md · 175 lines

How it starts

The opening of the file, as written. The whole thing — 175 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Writing E2E Tests

This skill is how we add an end-to-end test to the Opik E2E suite. You give it a feature, page, or branch; it runs a proven loop end-to-end and leaves you with a working, locally-verified Playwright test.

Announce at start: "I'm using the writing-e2e-tests skill to add an E2E test for X."

Where tests live

The suite is at tests_end_to_end/e2e/. Inside it:

Specs: tests/<feature>/<name>.spec.ts — one feature directory per page family (datasets, trace-explore, experiments, test-suites, online-evaluation, …).
Page Object Models: pom/<name>.page.ts — one class per page, methods for the interactions a test needs.
Fixtures: fixtures/<name>.fixture.ts — seed entities (project, dataset, trace, experiment, testSuite) and tear them down. Composed in a chain; re-exported from fixtures/index.ts.
SDK clients: core/sdk/ — sdkClient.python (HTTP wrapper over the bridge) and sdkClient.typescript (direct new Opik({...})) for seeding. core/backend/ holds the typed REST client for inspection + teardown.
Bridge: services/opik-sdk-driver/ — a FastAPI app (run with uv) wrapping the Python SDK, exposing routes the TS clients call. Playwright's webServer directive auto-spawns it during a test run; you don't start it by hand.

Specs and POMs import through path aliases: import { test, expect } from '@e2e/fixtures' and import { LogsPage } from '@e2e/pom/logs.page'.

Tooling — already set up

The Playwright MCP (live-UI exploration) and the playwright-test MCP (browser_generate_locator) are already configured in the repo's .mcp.json. No setup step.
Tests run via the plain Playwright CLI from tests_end_to_end/e2e/. The webServer directive spawns the bridge automatically.

Conventions

Read conventions.md before writing any POM or spec. It carries the rules that keep tests legible and stable: mandatory test.step() wrapping, UI-first assertions, selector preference, public-SDK-only seeding, fixture seed shapes, and the tag taxonomy. They aren't optional polish — each prevents a class of failure.

Read the full file on GitHub · 175 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

conventions.md 10 KB

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

4d ago First seen · 175 lines · 126 tokens per session scan A 281cba0ff01f

Subscribe to this mod's changes

writing-e2e-tests is a skill published in the GitHub repository comet-ml/opik (21,768 stars, last pushed today), licensed Apache-2.0. It adds 126 tokens to every session and 2,863 once invoked, about $0.0006 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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