How Visual Reverse Engineering Shortens the UAT Cycle by 60%

Most legacy modernization projects don’t fail during development; they fail during User Acceptance Testing (UAT). When 70% of legacy rewrites exceed their timelines or fail entirely, the culprit is almost always "undocumented tribal knowledge." You spend 18 months building what you think the system does, only to have users tell you in UAT that "it doesn't work like the old one."

The $3.6 trillion global technical debt isn't just bad code—it's the absence of a map. When 67% of legacy systems lack any form of up-to-date documentation, your engineers are forced into "software archaeology," manually digging through COBOL, Delphi, or jQuery spaghetti to find business rules. This manual process takes an average of 40 hours per screen.

How visual reverse engineering changes this equation is by moving the "Source of Truth" from the code to the user's actual behavior. By recording real workflows and extracting them into documented React components and API contracts, Replay shortens the UAT cycle by 60% or more.

TL;DR: Visual Reverse Engineering eliminates the "archaeology" phase of modernization by using video as the source of truth, reducing the UAT cycle by 60% through automated documentation and component generation.

The UAT Graveyard: Why Legacy Modernization Stalls#

In a traditional "Big Bang" rewrite, UAT is the first time the business sees the new system in action. This is where the "Documentation Gap" becomes a chasm. Because the original developers are gone and the documentation is non-existent, the new system inevitably misses edge cases that the legacy system handled implicitly.

The result? A never-ending cycle of "bug" reports that are actually missing features, leading to an average enterprise rewrite timeline of 18-24 months.

The Cost of Manual Extraction#

Manual reverse engineering is a massive drain on resources. An architect earns upwards of $150/hour; spending 40 hours per screen just to understand the state management and validation logic of a legacy form is a $6,000 expense per view. In a 100-screen application, you've spent $600,000 before a single line of modern code is even functional.

Replay reduces this to 4 hours per screen. By recording a user performing a task, the platform extracts the UI hierarchy, CSS variables, and business logic into a modern stack.

How Visual Reverse Engineering Works: From Black Box to React#

The "Visual" in Visual Reverse Engineering isn't just about screenshots. It’s about state transitions. When a user clicks "Submit" on a legacy insurance claims form, Replay records the network calls, the DOM mutations, and the client-side validation logic.

Step 1: Recording the Workflow#

Instead of interviewing stakeholders who might have forgotten how they use the system, you record them. This becomes the immutable "Source of Truth." Replay captures every interaction, ensuring that "hidden" features—like a specific field that only appears when a certain ZIP code is entered—are documented.

Step 2: Extraction and Component Generation#

The AI Automation Suite within Replay analyzes the recording to identify patterns. It recognizes a "Date Picker" or a "Data Grid" and maps it to your modern Design System (the Library).

typescript
// Example: Replay-generated React component from a legacy insurance portal
// This preserves the exact business logic extracted from the visual recording.

import React, { useState, useEffect } from 'react';
import { ModernInput, ModernButton, ModernAlert } from '@enterprise-ds/core';
import { validateClaimLogic } from './legacy-logic-bridge';

export const ClaimsFormMigrated = ({ initialData }) => {
  const [formData, setFormData] = useState(initialData);
  const [isEligible, setIsEligible] = useState(false);

  // Extracted Logic: The legacy system had a hidden rule where 
  // claims over $5000 required a secondary 'AdjusterID'
  useEffect(() => {
    if (formData.claimValue > 5000) {
      setIsEligible(true);
    }
  }, [formData.claimValue]);

  const handleSubmit = async (e) => {
    e.preventDefault();
    const isValid = await validateClaimLogic(formData);
    if (isValid) {
      // API Contract generated by Replay
      await fetch('/api/v1/claims/submit', {
        method: 'POST',
        body: JSON.stringify(formData)
      });
    }
  };

  return (
    <form onSubmit={handleSubmit} className="p-6 space-y-4">
      <ModernInput 
        label="Claim Amount" 
        type="number" 
        onChange={(val) => setFormData({...formData, claimValue: val})} 
      />
      {isEligible && (
        <ModernInput 
          label="Adjuster ID (Required for >$5k)" 
          required 
        />
      )}
      <ModernButton type="submit">Submit Claim</ModernButton>
    </form>
  );
};

💡 Pro Tip: Use Replay’s "Blueprints" editor to refine the generated code. It allows you to swap out generic components for your internal Design System components with one click.

Shortening UAT with Automated Documentation#

The primary reason UAT takes months is the "Verification Gap." Testers have to manually compare the old system and the new system side-by-side. Replay automates this by generating the documentation and E2E tests simultaneously.

Generating API Contracts#

One of the most painful parts of modernization is the backend. Often, the legacy API is a "black box." Replay’s AI Automation Suite monitors the network traffic during the recording and generates a Swagger/OpenAPI specification.

yaml
# Generated API Contract from Replay extraction
openapi: 3.0.0
info:
  title: Legacy Claims API
  version: 1.0.0
paths:
  /api/v1/claims/submit:
    post:
      summary: Extracted from User Workflow "Submit New Claim"
      parameters:
        - name: claimValue
          in: body
          schema:
            type: integer
            minimum: 0
      responses:
        '200':
          description: Success logic preserved

E2E Test Parity#

Replay doesn't just give you code; it gives you the test suite to prove the code works. It generates Playwright or Cypress tests based on the recorded workflow.

During UAT, instead of a human clicking through 500 scenarios, you run the generated suite. If the automated test passes, you know the modern component handles the data exactly like the legacy version did.

⚠️ Warning: Never assume your legacy API documentation is correct. Our data shows that 85% of legacy API docs are out of sync with the actual production behavior. Always use live traffic extraction.

The Architecture of Understanding: Flows and Blueprints#

Enterprise Architects need more than just components; they need to understand the Flow. Replay’s "Flows" feature maps the entire application architecture visually.

Mapping the "As-Is" State#

1. •Record: Capture all major user paths (Login -> Dashboard -> Report Generation).
2. •Audit: Replay performs a Technical Debt Audit, identifying which parts of the legacy UI are redundant.
3. •Blueprint: Create a visual map of how data moves between screens.
4. •Modernize: Export the entire flow as a set of React routes and components.

💰 ROI Insight: Companies using Replay see an average 70% time savings on the discovery and extraction phase. What used to take a quarter now takes two weeks.

Built for Regulated Environments#

Modernizing systems in Financial Services, Healthcare, or Government isn't just about speed; it's about compliance. Replay is built for these high-stakes environments.

• •SOC2 & HIPAA-ready: Data encryption at rest and in transit.
• •On-Premise Availability: For organizations that cannot send data to the cloud, Replay can run entirely within your firewall.
• •PII Masking: Replay automatically masks sensitive user data during the recording and extraction process, ensuring that no actual customer data is used in the generation of modern components.

Step-by-Step: Implementing Visual Reverse Engineering#

Step 1: Assessment and Scoping#

Identify the high-value, high-risk screens. Don't try to modernize everything at once. Focus on the workflows that cause the most support tickets or have the highest user volume.

Step 2: Recording the "Truth"#

Have subject matter experts (SMEs) record themselves performing the workflows. Capture the edge cases—the "weird" data entries that usually break new systems.

Step 3: Extraction via Replay#

Run the recordings through the Replay engine. The platform will output:

• •Documented React components
• •CSS/Theme variables
• •API Contracts (OpenAPI)
• •Business Logic documentation

Step 4: Verification and UAT#

Deploy the generated components into a staging environment. Because the components were built using the visual source of truth, the "Delta" between the old and new systems is minimized.

Step 5: Continuous Documentation#

As you iterate, Replay keeps your documentation updated. No more "archaeology" for the next generation of developers.

Frequently Asked Questions#

How long does legacy extraction take?#

With Replay, the time to move from a legacy screen to a documented React component is reduced from 40 hours (manual) to approximately 4 hours. For a standard enterprise module of 20 screens, you can have a functional prototype and documentation in less than two weeks.

What about business logic preservation?#

Replay captures client-side logic by observing state changes and DOM mutations. For server-side logic, Replay generates API contracts based on actual network traffic, ensuring the modern frontend interacts with the backend exactly as the legacy system did.

Does Replay work with mainframe or terminal-based systems?#

Yes. As long as there is a web-based or desktop UI layer that can be recorded, Replay can analyze the visual transitions and data patterns to generate modern UI equivalents.

Can we use our own Design System?#

Absolutely. Replay’s "Library" feature allows you to upload your Design System. During extraction, the AI maps legacy elements to your specific modern components (e.g., mapping a legacy

to your custom ).

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Ready to modernize without rewriting? Book a pilot with Replay - see your legacy screen extracted live during the call.