> ## Documentation Index > Fetch the complete documentation index at: https://docs.testdriver.ai/llms.txt > Use this file to discover all available pages before exploring further. # Debug > Diagnose failing tests with screenshots, replays, and logs ## Overview When a test fails, debug it by seeing exactly what happened — don't guess. TestDriver captures screenshots, video replays, and logs as your test runs, so you can replay the moment of failure instead of squinting at a stack trace. TestDriver MCP provides powerful commands to view and analyze the screenshots saved during test execution, enabling rapid debugging, test development, and comparison workflows without manually opening image files. **Automatic Screenshots (Default: Enabled)**: TestDriver automatically captures screenshots before and after every command. Screenshots are named with the line number and action, making it easy to trace exactly which line of code produced each screenshot. For example: `001-click-before-L42-submit-button.png` ## MCP Commands ### list\_local\_screenshots List and filter screenshots saved in the `.testdriver/screenshots/` directory: ``` list_local_screenshots() ``` **Filter Parameters:** Filter screenshots by test file or subdirectory (e.g., "login.test", "mcp-screenshots"). If omitted, lists all screenshots. Filter by exact line number from test file (e.g., 42 matches L42 in filename). Filter by line number range. Example: `{ start: 10, end: 20 }` matches screenshots from lines 10-20. Filter by action type: `click`, `find`, `type`, `assert`, `provision`, `scroll`, `hover`, etc. Filter by phase: `"before"` (state before action) or `"after"` (state after action). Regex pattern to match against filename. Example: `"login|signin"` or `"button.*click"`. Filter by exact sequence number. Filter by sequence range. Example: `{ start: 1, end: 10 }` matches first 10 screenshots. Maximum number of results to return (default: 50). Sort results by: `"modified"` (newest first, default), `"sequence"` (execution order), or `"line"` (line number). **Returns:** Array of screenshot metadata including: * `path` - Full absolute path to the screenshot file * `relativePath` - Path relative to `.testdriver/screenshots/` * `name` - Screenshot filename * `sizeBytes` - File size in bytes * `modified` - Last modification timestamp * `sequence` - Sequential number (from auto-screenshots) * `action` - Action type (click, find, etc.) * `phase` - Before/after phase * `lineNumber` - Line number from test file * `description` - Element or action description **Example Responses:** ```json theme={null} // Basic listing [ { "path": "/Users/user/project/.testdriver/screenshots/login.test/001-click-before-L42-submit-button.png", "relativePath": "login.test/001-click-before-L42-submit-button.png", "name": "001-click-before-L42-submit-button.png", "sizeBytes": 145632, "modified": "2026-01-23T10:00:00.000Z", "sequence": 1, "action": "click", "phase": "before", "lineNumber": 42, "description": "submit-button" } ] ``` ### view\_local\_screenshot View a specific screenshot from the list: ``` view_local_screenshot({ path: "/full/path/to/screenshot.png" }) ``` **Parameters:** Full absolute path to the screenshot file (as returned by `list_local_screenshots`) **Returns:** * Image content (displayed to both AI and user via MCP App) * Screenshot metadata * Success/error status ## Common Workflows ### Test Debugging After Failures When a test fails, you don't have to wonder what went wrong — use powerful filtering to quickly find the screenshots that show exactly what happened: **1. Find screenshots at the failing line:** ``` // If test failed at line 42 list_local_screenshots({ line: 42 }) // View before and after states at that line view_local_screenshot({ path: ".testdriver/screenshots/login.test/005-click-before-L42-submit-button.png" }) view_local_screenshot({ path: ".testdriver/screenshots/login.test/006-click-after-L42-submit-button.png" }) ``` **2. See what happened leading up to the failure:** ``` // Get screenshots from lines 35-45 to see context list_local_screenshots({ directory: "login.test", lineRange: { start: 35, end: 45 } }) ``` **3. Find all assertion screenshots:** ``` // See what the screen looked like during assertions list_local_screenshots({ action: "assert" }) ``` **4. View the final state before failure:** ``` // Get the last 5 screenshots in execution order list_local_screenshots({ directory: "login.test", sortBy: "sequence", limit: 5 }) ``` ### Finding Specific Actions When debugging element interactions: ``` // Find all click actions list_local_screenshots({ action: "click" }) // Find what the screen looked like BEFORE each click list_local_screenshots({ action: "click", phase: "before" }) // Find screenshots related to a specific element using regex list_local_screenshots({ pattern: "submit|button" }) // Find all type actions (for form filling issues) list_local_screenshots({ action: "type" }) ``` ### Understanding Test Flow View screenshots in execution order to trace test behavior: ``` // Get screenshots in execution order list_local_screenshots({ directory: "checkout.test", sortBy: "sequence" }) // Get just the first 10 actions list_local_screenshots({ sequenceRange: { start: 1, end: 10 }, sortBy: "sequence" }) // Get just the last 10 actions list_local_screenshots({ directory: "checkout.test", sortBy: "sequence", limit: 10 }) ``` ### Interactive Test Development While building tests using MCP tools, view screenshots to verify your test logic: 1. **After a test run**, filter screenshots to see specific actions: ``` // See all assertions list_local_screenshots({ action: "assert" }) // See what happened at a specific line you're debugging list_local_screenshots({ line: 25 }) ``` 2. **Review key points** in the test execution: ``` view_local_screenshot({ path: ".testdriver/screenshots/my-test.test/after-login.png" }) ``` 3. **Verify element locations and states** before adding assertions 4. **Iterate** - adjust your test code based on what you see in the screenshots ### Comparison and Analysis Compare screenshots to identify issues: **Using phase filtering for before/after comparison:** ``` // See state before all clicks list_local_screenshots({ action: "click", phase: "before" }) // See state after all clicks list_local_screenshots({ action: "click", phase: "after" }) ``` **Using line-based debugging:** ``` // Something went wrong around line 50 list_local_screenshots({ lineRange: { start: 45, end: 55 } }) ``` **Using regex patterns:** ``` // Find screenshots related to login functionality list_local_screenshots({ pattern: "login|signin|email|password" }) ``` ## Best Practices When saving screenshots in tests, use descriptive names to make them easier to identify: ```javascript theme={null} await testdriver.screenshot("initial-page-load"); await testdriver.screenshot("after-login-click"); await testdriver.screenshot("dashboard-loaded"); ``` Then when listing screenshots, you can quickly identify key moments without viewing every image. Always call `list_local_screenshots` first to see what's available. The list is sorted by modification time (newest first), making it easy to find recent test runs. When debugging a specific test, use the `directory` parameter to filter screenshots: ``` list_local_screenshots({ directory: "problematic-test.test" }) ``` This avoids clutter from other tests. When a test fails (especially with assertions), look at screenshots immediately before the failure. They show exactly what the AI or test "saw" at that moment, helping you understand why an assertion failed or why an element wasn't found. TestDriver test reports include screenshots in the timeline. Use MCP screenshot viewing for interactive debugging during development, and test reports for post-run analysis and team sharing. Remember that each test run clears its screenshot folder. If you need to preserve screenshots for comparison: ```bash theme={null} # Copy screenshots before next run cp -r .testdriver/screenshots/my-test.test .testdriver/screenshots-backup/ ``` ## Screenshot File Organization Understanding the directory structure helps with efficient screenshot viewing: ``` .testdriver/ screenshots/ login.test/ # Test file name (without .mjs extension) 001-find-before-L15-email-input.png # Auto: before find() at line 15 002-find-after-L15-email-input.png # Auto: after find() at line 15 003-click-before-L16-email-input.png # Auto: before click() at line 16 004-click-after-L16-email-input.png # Auto: after click() at line 16 login-complete.png # Manual: screenshot("login-complete") checkout.test/ 001-find-before-L12-add-to-cart.png 002-find-after-L12-add-to-cart.png ... ``` ### Automatic Screenshot Naming Format `---L-.png` | Component | Description | Example | | ------------- | -------------------------- | -------------------------- | | `seq` | Sequential number | `001`, `002` | | `action` | Command name | `click`, `type`, `find` | | `phase` | Before, after, or error | `before`, `after`, `error` | | `L` | Line number from test file | `L42` | | `description` | Element/action description | `submit-button` | ### Key Points * Each test file gets its own subdirectory * Automatic screenshots include line numbers for easy tracing * Manual `screenshot()` calls use custom names you provide * Folders are cleared at the start of each test run * All screenshots are PNG format * Disable automatic screenshots with `autoScreenshots: false` if needed ## Interaction List Sidebar (Source of Truth) When viewing a test run in the TestDriver console, the **interaction list sidebar** displays a screenshot for each interaction call (find, click, type, assert, etc.). These screenshots show exactly what was on the screen at the time each interaction was executed. **The sidebar screenshots are the source of truth.** If a test is behaving unexpectedly, check the screenshot attached to the specific interaction in the sidebar — it shows precisely what the AI saw when making its decision. This is more reliable than inferring screen state from test logs or local screenshots alone. Use the interaction list to: * **Verify what the AI saw** — confirm the correct page/state was visible when `find()` or `assert()` ran * **Debug misclicks** — see whether the target element was actually on screen * **Identify timing issues** — spot cases where the UI hadn't finished loading before an interaction fired * **Compare runs** — review interaction screenshots across multiple runs to catch flaky behavior ## Integration with Test Development ### During MCP Interactive Development When using TestDriver MCP tools (`session_start`, `find_and_click`, etc.), screenshots are automatically captured and displayed. Additionally, you can view previously saved screenshots: ``` # After test development session list_local_screenshots({ directory: "my-new-test.test" }) view_local_screenshot({ path: ".testdriver/screenshots/my-new-test.test/login-page.png" }) ``` This helps verify your test logic before running the full test file. ### After Test Runs When tests fail or behave unexpectedly, replay what happened step by step: 1. **Run the test** with `vitest run tests/my-test.test.mjs` 2. **List screenshots** using `list_local_screenshots` 3. **View relevant screenshots** to diagnose the issue 4. **Update test code** based on what you see 5. **Re-run and verify** the fix ## Troubleshooting If `list_local_screenshots` returns an empty array: * Ensure your test includes `await testdriver.screenshot()` calls * Verify the test actually ran (check test output) * Check that `.testdriver/screenshots/` directory exists * Confirm you're in the correct project directory If `view_local_screenshot` returns an error: * Verify the path is exactly as returned by `list_local_screenshots` * Check file permissions - ensure the screenshot file is readable * Confirm the file hasn't been deleted or moved If you have hundreds of screenshots making it hard to find what you need, use filtering: * Filter by test file: `list_local_screenshots({ directory: "my-test.test" })` * Filter by line number: `list_local_screenshots({ line: 42 })` or `list_local_screenshots({ lineRange: { start: 40, end: 50 } })` * Filter by action: `list_local_screenshots({ action: "click" })` * Filter by phase: `list_local_screenshots({ phase: "before" })` * Use regex: `list_local_screenshots({ pattern: "submit|login" })` * Limit results: `list_local_screenshots({ limit: 10 })` * Sort by line: `list_local_screenshots({ sortBy: "line" })` * Clean up old folders: `rm -rf .testdriver/screenshots/*` Remember that screenshot folders are cleared at the start of each test run. If you see old screenshots: * The test may not have run recently * Or the test failed before reaching the clearing logic * Manually clear: `rm -rf .testdriver/screenshots//` ## Where this fits in the Guide Debugging is what you reach for when a [Run](/v7/copilot/running-tests) goes sideways or a [Validate](/v7/making-assertions) assertion fails — the screenshots show you precisely what the AI saw before it acted. Once you've diagnosed the failure, the next step is to stop it from recurring. ## Related * [screenshot()](/v7/screenshot) - Capture screenshots during test execution * [Dashcam](/v7/dashcam) - Record full test sessions with video and logs * [assert()](/v7/assert) - Make AI-powered assertions that benefit from screenshot context ## Next You've seen what went wrong — now keep it from happening again. Let auto-healing repair flaky tests automatically before they fail your suite.