Preserve & Rerun (Compare)

When a test fails, the usual debugging loop is: rerun it, then compare two walls of logs to work out what changed. Preserve & Rerun collapses that into a single click. It snapshots the failing run and re-executes the test in one action, then shows both runs side-by-side in a Compare view aligned command-by-command - so you can see exactly where the two diverged without re-reading anything.

This is the fastest way to diagnose a flaky test: the command that behaved differently between the pass and the fail is highlighted for you, along with the assertion that broke.

Available across all three adapters - WebdriverIO, Selenium WebDriver, and Nightwatch.js.

Demo

How it works

1. Run your tests as normal. When a test finishes in a failed state, hover its row in the sidebar.
2. A bug-play icon (🐞▶) appears next to the regular ▶ rerun button. It only shows on failed test/suite rows, wherever a plain rerun is already supported (e.g. Cucumber scenarios at the scenario row, Mocha/Jasmine tests at the test or suite row).
3. Click it. DevTools captures a snapshot of the failing run, then re-launches just that test.
4. The Compare tab opens with the two runs aligned by command. The point of divergence and the assertion error (Expected vs Received) are called out.

Key Features

• One-click snapshot + rerun - Preserve the failing run and re-execute it in a single action, no code changes or full-suite restart.
• Command-by-command alignment - Both runs are laid out side-by-side and aligned by command, so differences stand out instantly.
• Failure point highlighted - Jumps you straight to the command where the two runs diverged.
• Assertion diff - Shows the assertion that broke with Expected vs Received side-by-side.
• Pop-out window - Open the comparison in a separate, themed window for a roomier view.
• Flaky-test triage - See which command differed between a pass and a fail without re-reading logs.

Limitations

• Cucumber: per-step rerun is disabled because Cucumber's --name filter targets scenarios, not individual Gherkin steps. Scenario-level Preserve & Rerun still works.