Error Reference

locator.click: Target page, context or browser has been closed

Playwright throws this when the page, context, or browser is torn down before an action resolves. It's almost always a missing await.

locator.click: Timeout 30000ms exceeded

The element never became actionable (visible, enabled, stable, receiving events) within Playwright's default 30s action timeout.

Error: strict mode violation: locator resolved to 2 elements

Playwright's strict mode refuses to act on a locator that matches more than one element instead of silently picking the first.

page.goto: net::ERR_CONNECTION_REFUSED

Playwright tried to navigate to a URL where nothing is listening yet. Usually the dev/test server wasn't ready.

Error: expect(locator).toBeVisible() failed

The assertion's own error message tells you which failure this is: read 'Received:' carefully before changing anything.

browserType.launch: Executable doesn't exist at .../chromium-XXXX/chrome-linux/chrome

Playwright's browser binaries were never installed, or don't match the Playwright version in package.json.

TimeoutError: waiting for selector "..." to be visible

This comes from the older page.waitForSelector API. It's the same actionability issue as a locator timeout, just an older call shape.

Error: locator.fill: Element is not an <input>, <textarea> or [contenteditable] element

fill() only works on real form controls, and the locator resolved to a wrapper element instead of the actual input.

Error: page.click: Element is outside of the viewport

The click target sits outside the configured browser viewport and couldn't be scrolled into a clickable position.

Error: net::ERR_ABORTED

The navigation was cancelled, either by a second navigation racing the first, or because the URL triggers a download instead of a page load.

Test timeout of 30000ms exceeded

This is the whole-test timeout, not a single action's. Something in the test hung or a step is genuinely slow.

Error: locator.click: Element is not attached to the DOM

The element you were about to click got unmounted and remounted between when it was found and when the action fired.

Error: browserContext.newPage: Target page, context or browser has been closed

You tried to open a new page in a context (or browser) that was already closed or crashed.

Error: locator.selectOption: Element is not a <select> element

selectOption() only works on native <select> elements, but this locator matched a custom dropdown component instead.

Error: element is not stable - waiting for element to stop moving

Playwright refuses to click a moving target because a CSS transition or animation is still running on the element.

Error: Playwright Test did not expect test() to be called here

Playwright found a test() call somewhere it can't register one. It's almost always two copies of @playwright/test, or a spec file importing another spec file.

Error: A snapshot doesn't exist at .../example.spec.ts-snapshots/home-chromium-linux.png, writing actual.

toHaveScreenshot() has no baseline image to compare against for this exact browser and OS combination, so it fails the first run and writes one.

page.goto: net::ERR_CERT_AUTHORITY_INVALID

The browser doesn't trust the TLS certificate of the site under test. Common with self-signed certificates on local, staging, and preview environments.

CypressError: Timed out retrying after 5000ms: cy.wait() timed out waiting for the 1st request to the route

The aliased request your test is waiting on never fired, usually because of a URL/method mismatch or a timing issue in the intercept setup.

CypressError: cy.click() failed because this element is detached from the DOM

The app re-rendered and replaced the element between when Cypress found it and when it tried to click it.

Cypress detected that the test has ended but there is still a pending command

A command started running but the test finished before it resolved, almost always caused by mixing native async/await with the Cypress command queue.

CypressError: Timed out retrying after 4000ms: Expected to find element: `...`, but never found it

The selector is either wrong, or the element renders later than Cypress's default retry window, so check for a pending network request first.

cy.visit() failed because you are attempting to visit a URL that is of a different origin

Cypress runs a test in one origin at a time, and the test tried to cross to a different domain mid-flow.

Cypress could not verify that this server is running

Cypress can't reach the URL configured as baseUrl. The app server either isn't up yet or is on a different port.

cy.type() failed because it requires a valid DOM element

The locator resolved to nothing (or to a detached element) right at the moment cy.type() tried to act on it.

CypressError: This element is not visible because it has CSS property: display: none

The target (or one of its ancestors) is hidden, usually a menu/dropdown item that only becomes visible after a real trigger interaction.

CypressError: cy.wait() timed out waiting for the 1st request to the route: `@getUsers`. No request ever occurred.

The alias cy.wait() is looking for never fired, so check for a typo between the intercept and the wait, or a request-order race.

Uncaught exception from application under test

The app under test threw an unhandled JS error, and Cypress fails the test by default when that happens.

CypressError: cy.click() failed because the center of this element is hidden from view

Another element (a sticky header, modal, or overlay) is sitting on top of the click target's center point.

AssertionError: Timed out retrying after 4000ms: expected false to be true

A generic retried assertion never became true in time. The real condition is whatever's asserted just above this line in the command log.

cy.request() failed trying to load: http://localhost:3000/api/... ECONNREFUSED

The API server that cy.request() is calling isn't reachable at that host/port.

CypressError: cy.origin() failed because your callback function returned a promise

cy.origin() callbacks must be synchronous, plain functions, with no async/await and no closures over outer-scope variables.

cy.type() failed because this element is disabled

Cypress is correctly refusing to type into a disabled field. This is usually a sign the app hasn't enabled it yet at this point in the flow.

Cypress detected that you returned a promise from a command while also invoking one or more cy commands in that promise.

Cypress commands aren't promises, and mixing them with real promises (async/await, fetch, .then returning a Promise) confuses its command queue.

cy.task('seedDb') failed with the following error: The task 'seedDb' was not handled in the setupNodeEvents method.

The spec called a task by name, but nothing registered a handler with that exact name in the Cypress config.

Cypress verification timed out.

Before its first run, Cypress starts its own binary to check that it works. On a slow or underpowered CI runner, that check takes longer than the default 30 seconds.

StaleElementReferenceException: stale element reference: element is not attached to the page document

The element you found earlier no longer exists in the current DOM, because the page re-rendered after you located it and before you acted on it.

NoSuchElementException: no such element: Unable to locate element

Selenium searched the current DOM for your locator and found nothing, and either the selector is wrong or the element hasn't rendered yet.

ElementClickInterceptedException: element click intercepted

Selenium found the element and tried to click it, but another element is currently on top of it at that point on the page.

TimeoutException: Expected condition failed: waiting for element to be clickable

The explicit wait's condition never became true within the timeout: the element stayed non-clickable (or absent) the whole time.

SessionNotCreatedException: session not created: This version of ChromeDriver only supports Chrome version XX

The installed ChromeDriver binary doesn't match the installed Chrome browser version.

WebDriverException: unknown error: cannot find Chrome binary

Selenium's ChromeDriver can't locate an actual Chrome (or Chromium) executable on this machine.

SessionNotCreatedException: Chrome failed to start: exited normally. (DevToolsActivePort file doesn't exist)

Chrome crashed during startup before ChromeDriver could connect to it. It almost always shows up when Chrome runs inside Docker or on a headless Linux CI runner.

ElementNotInteractableException: element not interactable

Selenium found the element in the DOM, but it can't be clicked or typed into right now: it's hidden, zero-sized, or not the element you actually meant.

SessionNotCreatedError: A new session could not be created

Appium rejected the session request. It's almost always a capabilities mismatch against what's actually available on the device/emulator.

NoSuchElementError: An element could not be located on the page using the given search parameters

The locator strategy (accessibility id, XPath, UiAutomator selector) didn't match anything in the current app screen.

Error: Could not find a connected Android device

Appium's UiAutomator2 driver couldn't see any device or emulator through ADB when the session started.

A session is either terminated or not started

The app crashed, or the Appium session was otherwise killed mid-test, and this command arrived after the session was already gone.

Neither ANDROID_HOME nor ANDROID_SDK_ROOT environment variable was exported

The Appium server process can't find the Android SDK, so it can't run adb or any other Android tool it needs to start a session.

xcodebuild failed with code 65

The XCUITest driver couldn't build WebDriverAgent, the helper app Appium installs on the device. On real iPhones this is almost always a code-signing problem.

Error: Request failed with status code 401

The API rejected the request as unauthenticated, and in test suites this is often a token lifecycle bug, not a credentials typo.

Error: timeout of 5000ms exceeded

The HTTP client gave up waiting for a response before the server replied, which could be a slow endpoint, a slow test environment, or a hung request.

Error: JSON schema validation failed: instance.price is not of a type(s) number

The response body doesn't match the contract your test expects, because the API is returning a different shape or type than the schema declares.

Error: Request failed with status code 409 (Conflict)

The API refused to create/update a resource because it already exists in that state, a common symptom of tests sharing data instead of isolating it.

SyntaxError: Unexpected token '<', "<!DOCTYPE "... is not valid JSON

The test expected JSON but the server sent back an HTML page. The real problem is whatever made the server return HTML, not the parsing.

Error: self-signed certificate in certificate chain

Node refused the HTTPS connection because a certificate in the chain was signed by a CA it doesn't trust, usually a corporate proxy or an internal company CA.

Error: connect ECONNREFUSED 127.0.0.1:3000

The test tried to hit a local server that isn't actually up yet in the CI environment, a classic 'works on my machine' parity gap.

Error: listen EADDRINUSE: address already in use :::3000

Something is already bound to the port your app/test server is trying to use on the CI runner.

Jest: A worker process has failed to exit gracefully

Something in the test run (an open handle, timer, or connection) is keeping the Node process alive after the tests themselves finished.

Error: Input required and not supplied: token

A GitHub Action in your workflow expects an input (often a token) that wasn't passed, usually a missing `with:` value or an unset secret.

FATAL ERROR: Reached heap limit Allocation failed - JavaScript heap out of memory

The Node process hit V8's heap size limit and crashed. In CI it usually shows up in big builds, TypeScript compiles, or long test runs with many workers.

Error: Process completed with exit code 137.

Exit code 137 means the process was killed with SIGKILL (128 + 9). In CI that's nearly always the kernel's OOM killer stepping in because the job ran out of memory.

npm ERR! `npm ci` can only install packages when your package.json and package-lock.json are in sync.

npm ci installs exactly what the lockfile says and refuses to guess. It stops when package.json lists something the lockfile doesn't match.