Comparison · AI testing agentsStably AI vs TesterArmy

Stably AI turns a sentence into Playwright code and proposes fixes when it drifts. TesterArmy's agent runs the sentence by looking at the screen.

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[01] Facts

At a glance

Stably AI posts credit amounts per plan at stably.ai/pricing, and docs.stably.ai shows the SDK, CLI, and GitHub Action, which is where the Playwright dependency is visible.

TesterArmytester.army

Approach: AI agent with vision, no selectors
Writing a test: Plain-English steps, CLI, MCP, or dashboard
Native mobile: iOS simulators + Android emulators
Public pricing: Free tier, then $99/mo self-serve
Pull requests: GitHub App: run per PR, check + comment

Stably AIstably.ai

Approach: AI locators inside standard Playwright
Writing a test: Plain English or recording, synced to Playwright
Native mobile: None documented, web only
Public pricing: Free $10 credits, then $60/mo
Pull requests: GitHub Action, PR comment with results

[02] Authoring

The same test, both ways

Stably's checkout is real Playwright with a selector on every line and one AI locator. TesterArmy's version is what a tester would say aloud, and a redesigned form changes nothing.

Stably AI · checkout.spec.ts

Write the guest checkout test with Stably's Playwright fixtures

Write(tests/checkout.spec.ts)

Created tests/checkout.spec.ts with 28 lines

1+added: import { test, expect } from '@stablyai/playwright-test';
2+added: 
3+added: test('checkout shows an order number', async ({ page }) => {
4+added:   await page.goto('https://staging.shop.example.com');
5+added:   await page
6+added:     .getByPlaceholder('Search')
7+added:     .fill('running shoes');
8+added:   await page.keyboard.press('Enter');
9+added:   await page.locator('[data-testid="product-card"]')
10+added:     .first()
11+added:     .click();
12+added:   await page
13+added:     .getByRole('button', { name: 'Add to cart' })
14+added:     .click();

… +14 lines

TesterArmy · the same test

Guest checkout shows an order numberPassedWeb1m 52s

Visit the home pageAct

Search for "running shoes" and open the first productAct

Add the product to the cart and go to checkoutAct

Check out as a guest with a valid US addressAct

Place the orderAct

The order confirmation page shows an order numberAssert

See it on your own app

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[03] Differences

Where they differ

Stably AI describes itself as standard Playwright with AI locators, AI assertions, a multi-page agent, and an autofix that proposes code changes. TesterArmy has no code under the sentence.

Code under the sentence

A Stably test is TypeScript with locators, and Autofix proposes a patch when the UI moves. A TesterArmy test is the plain-English steps themselves.

Native mobile coverage

Stably's docs cover web only. TesterArmy runs those steps on cloud-hosted iOS simulators and Android emulators, where Flutter, Expo, and React Native builds run.

Surfaces for coding agents

Stably's guide points Cursor or Claude Code at Playwright MCP to write code. TesterArmy gives those assistants its own MCP server plus a REST API.

Blocked as a verdict

Stably reports Playwright pass or fail, and Autofix sorts failures afterward. A TesterArmy run can end blocked when staging is down or a credential expired.

[04] Comparison

Side by side

Stably AI's tests stay Playwright files that run with npx playwright test anywhere, and the SDK drops into a suite you own. The table shows what owning those files costs.

DimensionTesterArmyStably AI

How you startTesterArmySign up, point the agent at your URL or upload a build, then run.Stably AISign up at app.stably.ai on Hobby, or install the SDK into a Playwright project.
How tests are writtenTesterArmyYou type plain-English steps in the dashboard, CLI, MCP server, or coding agent.Stably AIYou describe or record a flow and Stably syncs it to Playwright TypeScript.
Elements and driftTesterArmyThe agent sees the screen every run, so a renamed field needs no edit.AdvantageStably AIStandard locators drive tests, getLocatorsByAI adapts to DOM changes, and Autofix proposes fixes.
Pull request testingTesterArmyThe GitHub App tests each PR and posts a check and comment with video.Stably AIThe stably-runner-action posts results as a PR comment, and a guide covers GitLab CI.
Agent and API surfacesTesterArmyYour coding agent gets a CLI, a hosted MCP server, and a REST API.AdvantageStably AIThe CLI creates, runs, and fixes tests; the docs list no hosted MCP server.
Native mobileTesterArmyUpload a zipped .app or an .apk and the steps run on cloud simulators.AdvantageStably AIThe docs cover Playwright browser tests and do not mention native mobile.
Test portabilityTesterArmyTests are plain-English JSON kept in your repo, but only TesterArmy's agent runs them.Stably AIEvery test is standard Playwright, so any machine or CI with Playwright runs it.Advantage
PricingTesterArmyAfter the free tier, $99 a month buys 250 runs and $299 buys 1,000.Stably AITeam costs $60 a month, and Stably estimates $0.05 to $0.15 per typical test.Advantage

Facts checked September 2026. Spotted something out of date? Tell us and it gets fixed.

[05] What it costs

Pricing

Stably meters credits per browser minute and AI token, and estimates $0.05 to $0.15 per typical test. TesterArmy counts runs per month and ignores how long each run takes.

TesterArmy

$99/mo after a free tier

Free tier: sign up and run against your own app
Hobby $99/mo: up to 250 test runs included, web and mobile
Startup $299/mo: up to 1,000 test runs included, 10 concurrent test runs

Full pricing

Stably AI

$60/mo after a free tier

Hobby: $0 per month, $10 of credits, 1 concurrent browser
Team: $60 per month, $60 of credits, up to 50 concurrent browsers
Growth: $250 per month, $250 of credits, up to 100 concurrent browsers

[06] Fit

Who should pick which

Pick by what you want left on disk after you describe a flow. Stably leaves a Playwright file and TesterArmy leaves the plain-English steps.

Pick TesterArmy ifPick Stably AI if

Pick TesterArmy ifYou want the plain-English steps to be the whole test, with no Playwright suite to own.Pick Stably AI ifYou already run Playwright and want AI locators, assertions, and autofix inside the code you have.
Pick TesterArmy ifYou ship iOS or Android builds and want them tested in the same format as your web app.Pick Stably AI ifYou want tests that stay portable Playwright and run on any machine or CI.
Pick TesterArmy ifYour coding agent should create and run tests through a hosted MCP server or REST API.Pick Stably AI ifYou want credit-metered pricing with up to 50 concurrent browsers on the $60 plan.

Already on Stably AI?

Give your coding agent one prompt and it turns each Stably spec into act and assert steps, minus the locators, then runs them against your app.

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[07] FAQ

Questions

Stably AI sits on Playwright. You describe a flow, it writes a Playwright test with AI locators, and Autofix proposes patches when the UI drifts. TesterArmy runs plain-English steps with an agent on web or mobile, with no code.

TesterArmy can replace Stably for end-to-end web testing and adds native mobile builds, which Stably's docs do not mention. Each product is self-serve, has a free plan, and posts results on pull requests. Stably's tests run as plain Playwright anywhere.

Stably meters credits on a free Hobby plan and a $60 Team plan, estimating $0.05 to $0.15 per typical test. TesterArmy sells runs, $99 a month for 250 or $299 for 1,000, so a short test costs less on Stably.

Stably keeps them. Install the @stablyai/playwright-test SDK and current tests keep running, with AI primitives added where you want. TesterArmy does not run Playwright files, so you describe each flow in plain English and retire the suite as coverage grows.

Stably wins on portability and price for web suites. Every test is standard Playwright that runs on any machine or CI, the SDK drops into an existing suite, and Team costs $60 a month with up to 50 concurrent browsers.

Each Stably spec holds one flow, and your coding agent can restate it as act and assert steps without the locators. Logins become encrypted credentials. Keep the JSON beside the specs until the plain-English flows cover them.