Codeceptjs Fundamentals

CodeceptJS Fundamentals

Two jobs, in order: learn the rules below, then discover what this project has configured.

Gate

• CodeceptJS 4 is ESM/TypeScript only; tests, configs, page objects, helpers use import/export.
• No "type": "module" in package.json → add it before anything else.
• TypeScript: config codecept.conf.ts, TS loader entry in require: [...].
• Project on 3.x or CommonJS (require(), removed plugins like autoLogin, helper Nightmare) → stop, recommend migrate-codeceptjs-4. Don't patch files piecemeal — migration is whole-project.

Main rule

• Tests are written from the user's perspective: a linear scenario of actions, readable as prose.
  • Good: I.click('Login'), I.fillField('Email', ...), I.see('Welcome')
• Tests are declarative, helpers imperative — recommended layering:
  • Scenario shows what the user does via I.*; implementation details live below
  • Low-level access (this.helpers['Playwright'].page, fetch, filesystem) works fine inside a Scenario, but it's recommended to push it into a helper and expose one I.* action instead
• Keep tests short: repeated sequences → actor method, page object, or step object.
• Prefer semantic locators over selectors so tests survive markup churn.

Where things go (recommended placement)

• Site-wide actions (login, dropdowns, rich text editors) → actor file (custom steps)
• Page/screen actions + locators → page object; SPA screen = one page object
• Site-wide widgets (nav, modals, datepickers) → page fragments / component objects
• Low-level driver access (DB connections, email, filesystem, complex mouse) → helper
• Data creation/cleanup via API → data objects (REST/GraphQL helper + _after() cleanup), or ApiDataFactory (I.have(...))
• Don't overengineer: no page object until an abstraction is reused across tests.

Shortcuts

• Login needed → autoLogin plugin or actor method, not inline steps per test
• Test data → create via API before the test, not through the UI
• Long test → break into several; long tests are fragile and hard to follow
• Optional UI element / conditional flow → await tryTo(...) instead of if (await I.grab...) — keeps scenarios linear

Architecture

• Config: codecept.conf.{js,ts,mjs,cjs} at repo root; multiple files selected via --config <file>.
• Helpers execute; I delegates. Every I.<method> is routed to whichever active helper implements it (Playwright, WebDriver, Puppeteer, Appium share one API surface). Active helpers = keys under helpers. Tests call the actor, never the engine — backends stay swappable.
• DI container — why it exists:
  • Everything shared (actor, helpers, page objects, support objects) registers under one container; include maps names → modules
  • Classes are auto-instantiated by the container — no new, no manual wiring
  • inject() returns lazy proxies: destructuring at module top resolves at call time, so circular page-object references work where plain import would give undefined
  • Access: destructure in Scenario signature (Scenario('...', ({ I, loginPage }) => ...)) or const { I } = inject() once per file
• Custom helpers extend Helper, register under helpers, add new I.* methods.
  • I does not exist inside a helper. Compose via this.helpers['<HelperName>'] (e.g. this.helpers['Playwright'].page, this.helpers['REST'].sendGetRequest(...)).
• Plugins are event listeners on lifecycle events (suite.*, test.*, step.*, hook.*, multiple.*). Full list: node_modules/codeceptjs/lib/event.js. Register under plugins with enabled: true.

Config mutation trap

• @codeceptjs/configure mutates resolved config at load time (setHeadlessWhen, setBrowser, ...). Static values can lie — grep for its import before trusting show: / browser: fields.
• setCommonPlugins(): enables retryFailedStep + screenshot; registers (off until -p) pause, browser, aiTrace, heal.

Plugins worth knowing

• retryFailedStep — retries transient step failures
• screenshot — screenshots on failure; slides: true → output/records.html slideshow
• pageInfo — dumps URL/HTML/console on failure
• auth — session reuse for login (see codeceptjs-auth skill)
• aiTrace — per-step screenshots/HTML/ARIA/console for AI debugging
• pause — interactive pause
• heal — AI-suggested fixes for broken steps (off in --debug)
• screencast — video of the run
• customLocator — maps $name prefix to team's test attribute (data-testid, data-qa)
• browser — CLI-only override of browser helper config (see below)

Note: tryTo, retryTo, eachElement are not plugins in 4.x — import them from codeceptjs/effects.

Plugins from CLI

Any plugin can be enabled/reconfigured per-run with -p <plugin>, args chained with ::

npx codeceptjs run -p aiTrace                    # enable for this run
npx codeceptjs run -p screenshot:on=step         # reconfigure inline
npx codeceptjs run -p pause:on=file:path=tests/login_test.js;line=43

• screenshot, pause, aiTrace, heal share an on= trigger: fail (default except aiTrace) | step | test | file:path=...;line=N | url:pattern=<glob>
• browser plugin overrides without touching config — CI matrix legs, one-off env variants:
  • -p browser:hide / -p browser:show / -p browser:browser=firefox / -p browser:windowSize=1280x800
  • Requires @codeceptjs/configure

Effects (codeceptjs/effects)

Flow-control functions imported from codeceptjs/effects. In 4.x these are no longer plugins/globals.

• tryTo(() => ...) — runs steps that may fail without stopping the test; returns boolean.
  • Prefer tryTo over if: scenarios should stay linear — instead of branching on a grabbed value to decide whether a UI state exists, attempt the optional steps and branch on the boolean result:

    const banner = await tryTo(() => { I.see('Cookie banner'); I.click('Accept cookies') })
    if (!banner) I.say('No cookie banner')
    

  • Auto-retries are disabled inside tryTo blocks.
• retryTo(() => ..., maxTries, pollInterval = 200) — retries a step block until it succeeds (flaky elements, animations); callback receives the current attempt count.
• hopeThat(() => ...) — soft assertions (see Assertions); end with hopeThat.noErrors().
• within(locator | { frame }, fn) — scopes resolution to subtree or iframe; can return values (await). Prefer the context parameter of individual actions (I.click('Save', '.toolbar')) when possible — reserve within for genuinely scoped blocks.

All effects return Promises — await them.

Element-based API (codeceptjs/els)

Hybrid style: mix I.* with direct element access. Import { element, eachElement, expectElement, expectAnyElement, expectAllElements } from 'codeceptjs/els'.

• element(locator, async el => { ... }) — scoped access to one element; chain el.$(locator) into children without re-querying
• eachElement(locator, async (el, index) => ...) — iterate collections
• expectElement / expectAnyElement / expectAllElements(locator, fn) — custom conditions
• Elements are WebElement wrappers — same API on all helpers: getText(), getAttribute(), isVisible(), isEnabled(), getBoundingBox(), exists(), $$()
• Optional purpose string improves debug logs: element('verify discount applied', '.price', ...)
• Use when built-ins don't cover it: collections, layout checks (getBoundingBox), per-element loops, chaining ops on one element. Prefer I.* for readability otherwise.

Writing tests

• Structure: one Feature(...) per file, one or more Scenario(...) inside. No nested suites, no multiple Features per file.
• Hooks: Before, After, BeforeSuite, AfterSuite, Fail(...).
• Page object lifecycle hooks: _before() (lazy, once per test, on first use), _after() (skipped if unused), _beforeSuite(), _afterSuite().
• await required for: grab* methods, imported functions, page-object methods containing async ops (elsewhere: unhandled rejections). Never for plain action steps — the recorder chains them.
• Secrets: I.fillField('Password', secret(process.env.PASSWORD)) — masks logs, traces, AI prompts. Import from codeceptjs.
• Sessions: session(name, fn) — parallel browser context for multi-user Scenarios (chat, multi-tenant).

Locators

• ARIA locators are strongest — resilient to CSS refactors, describe what the user sees:
  • I.click({ role: 'button', name: 'Save' })
• Actions accept plain strings (visible text, label, placeholder, name, aria-label) or objects ({ css }, { xpath }, { id }).
• Plain string already matches aria-label — no 'aria-label=...' prefix needed.
• Pass context as last argument — scoped semantic locator beats long unscoped one:
  • I.click('Save', '.toolbar') not I.click('#toolbar .btn-save')
• Avoid style-based class names (.bg-green); prefer semantic ones (.btn-save).
• data-testid/data-qa apps → enable customLocator, write $name.
• No semantic name fits → locate(...) builder (.withClass, .withText, .inside, .and): locate('.button').withText('Click me').

Waiting

• Action steps auto-wait for existence + interactability. Add explicit waitFor* only when the condition isn't tied to an interaction (modal after network call, spinner hiding).
• Avoid I.wait(N) — last resort.

Assertions

Built-in browser assertions come first: I.see, I.seeTextEquals, I.seeElement, I.seeInField, I.seeNumberOfElements, I.seeInCurrentUrl (+ dontSee* counterparts). Clear failures, recorder-integrated. see matches visible text; hidden DOM content needs seeInSource / seeElementInDOM.

For what built-ins don't cover, in order of preference:

1. Reusable custom assertion in a helper — I.seeTableIsOrdered('Price', 'desc'); name positives see*, negatives dontSee*; use codeceptjs/assertions inside, never raw throw new Error()
2. ExpectHelper (@codeceptjs/expect-helper) — chai matchers on I: I.expectEqual, I.expectDeepEqualExcluding, I.expectMatchesPattern, I.expectJsonSchema; appears in step log like other steps
3. codeceptjs/assertions directly — dependency-free factories: equals(subject).assert(actual, expected) / .negate(...); failure messages match I.see formatting
4. Any library on grabbed data (grab* always needs await) — chai/jest/node:assert; fails the test but won't show as a step

Soft assertions: hopeThat(() => I.see(...)) from codeceptjs/effects — logs each failure and continues; end with hopeThat.noErrors() to fail if any were recorded.

Parallel runs

• run-workers <N> — splits Scenarios across worker threads
• run-multiple <profile> — profiles via multiple block in config (browsers, viewports)

Config organization (recommended)

• Multiple config files per environment (codecept.conf.js, codecept.ci.conf.js, ...); share parts via modules in a config/ dir
• .env files + dotenv for secrets/env-specific values
• Bulk-register page objects/components by spreading exported maps into include
• Pass data from config/bootstrap into tests via codeceptjs.container.append({ testUser }) — injectable by name

Discover this project

In order; skipping steps produces wrong guesses:

1. Verify setup loads: npx codeceptjs check -c <config> — validates everything; output doubles as inventory. Fix failures before continuing.
2. Read the active config: helpers (+ browser/baseURL/viewport/env-driven values), plugins (incl. anything setCommonPlugins() injects), AI provider + required env var, env selection mechanism, page objects from include, custom helpers.
3. List actions: npx codeceptjs list -c <config> (--docs adds JSDoc; --action <name> for one). The actual I.* surface differs from built-ins when custom helpers exist — always check before suggesting a method.
4. List tests: npx codeceptjs dry-run -c <config> — --steps shows queued actions, --grep filters, --numbers gives per-test step indices matching MCP pauseAt.
   • ⚠ dry-run --grep and run --grep do not select the same set (4.1.0): run --grep matches Feature + Scenario, dry-run --grep matches the Scenario title only. dry-run --grep 'Dialogs' lists 0 tests where run --grep 'Dialogs' executes all 11. Never size a run from a dry-run's grep, and target a whole Feature by file path (run tests/foo_test.ts) when the selection must be exact.

Gherkin projects: npx codeceptjs gherkin:steps -c <config>.

Reference docs live under node_modules/codeceptjs/docs/ — read them instead of guessing APIs.

Report

Short prose summary. Must include:

• Env-driven values flagged as env-driven (process.env.BROWSER || 'chromium', not just 'chromium')
• Conflicts flagged (static show: true vs setHeadlessWhen(CI); auth configured but credential env vars missing)
• No config at root and no --config referenced → recommend npx codeceptjs init ., stop
• 3.x/CommonJS detected → recommend migrate-codeceptjs-4, stop