/testdriver-errors

name: testdriver:errors
description: Custom error classes and error handling

<!-- Generated from errors.mdx. DO NOT EDIT. -->

Overview

TestDriver gives custom error classes with full debug information. The SDK exports them. You can use them for `instanceof` checks in your tests.

import TestDriver, { ElementNotFoundError, AIError } from 'testdriverai';

ElementNotFoundError

TestDriver throws this when `find()` cannot find an element on the screen. It also throws this when you call `click()` or `hover()` on an element that TestDriver did not find.

try {
  await testdriver.find('nonexistent button').click();
} catch (error) {
  if (error instanceof ElementNotFoundError) {
    console.log(error.description);       // "nonexistent button"
    console.log(error.screenshotPath);    // path to debug screenshot
    console.log(error.pixelDiffPath);     // path to pixel diff image
  }
}

Properties

<ParamField path="name" type="string"> Always `"ElementNotFoundError"`. </ParamField>

<ParamField path="message" type="string"> A message with a debug block. The block has the element description, the cache status, the similarity scores, and the AI response details. </ParamField>

<ParamField path="description" type="string"> The original element description passed to `find()`. </ParamField>

<ParamField path="screenshotPath" type="string | null"> Absolute path to a debug screenshot saved at the time of failure. Written to `<os.tmpdir>/testdriver-debug/screenshot-<timestamp>.png`. </ParamField>

<ParamField path="pixelDiffPath" type="string | null"> Absolute path to a pixel diff image showing the comparison between the cached and current screenshots. Written to `<os.tmpdir>/testdriver-debug/pixel-diff-error-<timestamp>.png`. Only present when cache was involved. </ParamField>

<ParamField path="cachedImagePath" type="string | null"> URL to the cached image that was compared against. </ParamField>

<ParamField path="aiResponse" type="object | null"> Sanitized AI response object. Large binary fields (`croppedImage`, `screenshot`, `pixelDiffImage`) are removed. Contains cache metadata like `similarity`, `cacheHit`, `cacheStrategy`, `cacheDiffPercent`, and `threshold`. </ParamField>

<ParamField path="timestamp" type="string"> ISO 8601 timestamp of when the error was created. </ParamField>

Enhanced Message

The error message is automatically enhanced with debugging information:

Element not found: "submit button"

=== Element Debug Info ===
Element: submit button
Cache Hit: false
Similarity: 0.23
Cache Strategy: pixel-diff
Threshold: 0.05
AI Response Element: null

Stack Trace Cleaning

Stack traces are automatically cleaned to remove internal SDK frames (`Element.*`, `sdk.js` internals), showing only your test code for easier debugging.

AIError

Thrown when `act()` exhausts all retry attempts.

try {
  await testdriver.act('perform complex workflow', { tries: 3 });
} catch (error) {
  if (error instanceof AIError) {
    console.log(error.task);       // "perform complex workflow"
    console.log(error.tries);     // 3
    console.log(error.duration);  // 15234 (ms)
    console.log(error.cause);     // underlying Error
  }
}

Properties

<ParamField path="name" type="string"> Always `"AIError"`. </ParamField>

<ParamField path="message" type="string"> Enhanced message with execution details block. </ParamField>

<ParamField path="task" type="string"> The task description passed to `act()`. </ParamField>

<ParamField path="tries" type="number"> Number of attempts that were made. </ParamField>

<ParamField path="maxTries" type="number"> Maximum number of attempts configured. </ParamField>

<ParamField path="duration" type="number"> Total execution time in milliseconds. </ParamField>

<ParamField path="cause" type="Error | undefined"> The underlying error that caused the final failure. </ParamField>

<ParamField path="timestamp" type="string"> ISO 8601 timestamp of when the error was created. </ParamField>

Enhanced Message

AI failed: Element not found after 3 attempts

=== AI Execution Details ===
Task: perform complex workflow
Tries: 3 / 3
Duration: 15234ms
Cause: ElementNotFoundError: Element not found: "submit button"

Internal Error Classes

These errors are used internally by the agent and are not exported, but may appear as the `cause` of an `AIError`:

MatchError

Thrown when element matching fails (text, image, or assertion).

| Property | Type | Description | |---|---|---| | `fatal` | `boolean` | If `true`, cannot be healed. Default: `false` | | `attachScreenshot` | `boolean` | Always `true` — a screenshot is attached to the error |

CommandError

Thrown for invalid arguments or unsupported operations.

| Property | Type | Description | |---|---|---| | `fatal` | `boolean` | Always `true` | | `attachScreenshot` | `boolean` | Always `false` |

Soft Assert Mode

Inside `act()`, assertions run in **soft assert mode**. When an assertion fails, it returns the failure result instead of throwing, allowing the AI to process the failure and adjust its approach.

// Inside act(), assertion failures don't throw
await testdriver.act('verify the dashboard shows correct data', {
  tries: 3,
});
// The AI can see assertion results and self-correct

This is automatic — you don't need to configure it. Regular `assert()` calls outside of `act()` will throw normally on failure.

Error Handling Patterns

Catching Specific Errors

import TestDriver, { ElementNotFoundError, AIError } from 'testdriverai';

try {
  await testdriver.find('submit button').click();
} catch (error) {
  if (error instanceof ElementNotFoundError) {
    // Element wasn't found — check screenshot for debugging
    console.log('Debug screenshot:', error.screenshotPath);
  } else if (error instanceof AIError) {
    // AI exhausted retries
    console.lo