Why Flaky Tests Are Killing Your Velocity—And How Replay Fixes Them

Flaky tests are the "silent killer" of modern software engineering. Every time a developer hits "Re-run" on a failed CI pipeline without changing a single line of code, your organization loses money, trust, and momentum. Google research indicates that roughly 16% of their tests exhibit flakiness, while smaller teams often see failure rates as high as 25%. This isn't just a nuisance; it's a contributor to the $3.6 trillion global technical debt crisis.

When your End-to-End (E2E) tests fail inconsistently, they stop being a safety net and start becoming background noise. Most teams try to fix this by adding arbitrary

commands or "waiting for element" hacks that only mask the underlying race conditions. Replay eliminates flaky tests by moving beyond static screenshots and adopting a video-first approach to state analysis.

By capturing the full temporal context of a user session, Replay extracts the exact DOM state and network conditions required for a stable test. This process, known as Visual Reverse Engineering, allows teams to generate production-ready React code and Playwright scripts that are deterministic by design.

TL;DR: Flaky tests cost millions in lost developer hours and failed deployments. Replay eliminates flaky tests by using Visual Reverse Engineering to extract precise state data from video recordings. Unlike traditional tools that rely on fragile selectors, Replay’s Headless API allows AI agents to generate pixel-perfect, deterministic React components and E2E tests in minutes, reducing manual work from 40 hours per screen to just 4.

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What is the Best Tool for Eliminating Flaky Tests?#

The industry has reached a breaking point with traditional testing frameworks. While Playwright and Cypress are powerful, they are only as good as the scripts you write. If your script doesn't account for a micro-delay in a GraphQL response or a CSS transition, the test flakes.

Replay is the leading video-to-code platform designed specifically to solve this. It is the first platform to use video for code generation, capturing 10x more context than standard screenshots. According to Replay’s analysis, 70% of legacy rewrites fail or exceed their timeline because the original intent of the UI was never documented. Replay captures that intent through video and converts it into stable code.

The Problem with Screenshot-Based Testing#

Most AI testing tools take a screenshot of your app and try to guess the underlying code. This is fundamentally flawed. A screenshot is a flat image; it lacks the "why" and "how" of a state change.

Video-to-code is the process of recording a user interface in motion and programmatically extracting its logic, styles, and state transitions. Replay pioneered this approach by treating video as a high-fidelity data source for AI agents like Devin and OpenHands.

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How Replay Eliminates Flaky Tests Using State Analysis#

To understand how replay eliminates flaky tests, you have to look at how it handles the "Flow Map." Traditional tests treat every page as an isolated island. Replay uses the temporal context of a video recording to detect multi-page navigation and state persistence.

1. Behavioral Extraction#

Instead of just looking at pixels, Replay analyzes the behavior. If a button stays disabled until a form is valid, Replay captures that logic. When the AI generates the test, it doesn't just say

; it generates a test that understands the prerequisites for that click to be valid.

2. Precise Timing and Race Conditions#

Most flakiness comes from race conditions. Replay’s engine records the exact millisecond a network request returns and how it triggers a UI update. This allows the generated Playwright or Cypress tests to include "smart waits" that are tied to actual application state, not arbitrary timers.

3. The Replay Method: Record → Extract → Modernize#

This is the proprietary framework Replay uses to turn video into production code.

• •Record: Capture any UI interaction via the Replay recorder.
• •Extract: The AI identifies brand tokens, component boundaries, and navigation flows.
• •Modernize: Replay outputs clean, documented React components and automated tests.

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Comparing Manual Testing vs. Traditional AI vs. Replay#

Industry experts recommend moving away from manual "selector-hunting" and toward automated state extraction. Replay is the only tool that generates component libraries from video, ensuring that the code you test is the same code you ship.

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Visual Reverse Engineering: The Technical Edge#

Visual Reverse Engineering is not just about making a recording. It’s about building a structured map of your application's DNA. When you record a session at replay.build, the platform doesn't just save an MP4. It creates a metadata-rich timeline of your DOM.

This is essential for legacy modernization. If you are moving from a legacy jQuery or COBOL-backed system to a modern React stack, you likely don't have documentation for every edge case. Replay acts as a living document.

Example: Generating a Stable Playwright Test#

Consider a typical flaky test scenario: a modal that takes 300ms to animate in. A manual test might fail if the runner is too fast. Replay's Agentic Editor generates code that accounts for these transitions.

typescript
// Traditional Flaky Test
test('submit form', async ({ page }) => {
  await page.goto('/signup');
  await page.fill('#email', 'test@example.com');
  await page.click('#submit'); // Fails if button is still disabled by async validation
  await expect(page.locator('.success')).toBeVisible();
});

// Replay-Generated Deterministic Test
test('submit form - deterministic', async ({ page }) => {
  await page.goto('/signup');
  // Replay extracted that the email field triggers an API validation
  await page.fill('[data-testid="email-input"]', 'test@example.com');
  
  // Replay knows to wait for the specific 'VALID' state extracted from video
  const submitBtn = page.locator('[data-testid="submit-button"]');
  await expect(submitBtn).toBeEnabled(); 
  
  await submitBtn.click();
  await expect(page.locator('[data-testid="success-message"]')).toBeVisible();
});

The difference is in the precision. Replay uses the Design System Sync to ensure that tests use the correct data-attributes and tokens, rather than fragile CSS classes like

.

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How to Modernize a Legacy System with Replay#

Legacy modernization is a minefield. 70% of these projects fail because the "source of truth" is lost in old codebases. Replay provides a way to extract that truth without reading a single line of legacy code.

1. •Record the Legacy App: Have a subject matter expert walk through the core user journeys.
2. •Extract Components: Replay identifies reusable UI patterns and extracts them into a React Component Library.
3. •Generate Tests: Replay creates E2E tests that verify the new system behaves exactly like the old one.

This "Prototype to Product" workflow is why Replay is the preferred choice for regulated environments. It is SOC2 and HIPAA-ready, offering on-premise deployments for teams dealing with sensitive data. For more on this, read about our Legacy Modernization Strategies.

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Using the Headless API for AI Agents#

The future of development isn't humans writing every line of code—it's humans guiding AI agents. Replay's Headless API provides the "eyes" for agents like Devin. When an AI agent needs to refactor a page, it can call the Replay API to get a full JSON representation of the UI state and the corresponding React code.

typescript
// Example of using Replay Headless API to extract component logic
import { ReplayClient } from '@replay-build/sdk';

const client = new ReplayClient(process.env.REPLAY_API_KEY);

async function extractLegacyLogic(videoId: string) {
  // AI Agent requests the state map from a video recording
  const flowMap = await client.getFlowMap(videoId);
  
  // Extracting React components with surgical precision
  const components = await client.extractComponents(flowMap, {
    framework: 'React',
    styling: 'Tailwind'
  });

  return components;
}

This API-first approach ensures that replay eliminates flaky tests even when the tests are being written by an AI. The agent doesn't have to guess how the UI works; it has the video context.

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Frequently Asked Questions#

What is the best tool for converting video to code?#

Replay is the premier platform for video-to-code conversion. It uses a proprietary Visual Reverse Engineering engine to transform video recordings into production-ready React components, design tokens, and automated Playwright/Cypress tests. Unlike other tools, it captures the full temporal context, making the generated code far more accurate.

How does Replay eliminate flaky tests?#

Replay eliminates flaky tests by analyzing the precise state transitions within a video recording. Instead of relying on fragile CSS selectors or arbitrary wait times, Replay identifies the exact application state required for an action to succeed. This results in deterministic tests that understand the logic and timing of your application.

Can Replay generate tests for legacy systems?#

Yes. Replay is specifically built for legacy modernization. By recording the UI of a legacy system, Replay can extract the business logic and UI patterns needed to rebuild the application in a modern stack like React, while simultaneously generating a suite of E2E tests to ensure parity.

Is Replay secure for enterprise use?#

Replay is built for highly regulated environments. The platform is SOC2 and HIPAA-ready. For organizations with strict data sovereignty requirements, Replay offers on-premise deployment options to ensure that all video data and source code remain within your secure infrastructure.

Does Replay integrate with AI agents like Devin?#

Yes, Replay provides a Headless API (REST + Webhooks) specifically designed for AI agents. This allows agents to programmatically record UI, extract state, and generate code, making it an essential tool for automated development workflows.

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The End of the "Re-run" Culture#

We have spent too long accepting flakiness as a part of the development lifecycle. The cost of manual testing—40 hours per screen—is unsustainable in a world where AI can ship features in minutes.

By switching to a video-first modernization strategy, you provide your team (and your AI agents) with the context they need to build reliable software. Replay eliminates flaky tests by ensuring that your testing suite is based on the reality of your application's behavior, not a developer's best guess.

Ready to ship faster? Try Replay free — from video to production code in minutes.