Your 10-Point Pre-Migration Checklist: What Every Team Must Audit Before a Framework Switch

Every framework migration starts with good intentions. The promise of better performance, a more active ecosystem, or easier hiring pushes teams to consider the switch. But without a structured pre-migration audit, what should be a planned transition often turns into a crisis. We've seen teams lose weeks to broken builds, discover critical dependencies that have no equivalent in the new framework, or realize halfway through that their test suite covers the wrong things. This guide lays out a 10-point checklist to audit before you commit to a framework switch. Each point is designed to catch risks early, when they are still cheap to fix.

1. Why a Pre-Migration Audit Matters and What Happens Without It

Migrating a production application from one framework to another is fundamentally different from starting a greenfield project. The existing codebase carries years of implicit decisions, workarounds, and hidden assumptions. A pre-migration audit surfaces these before they become blockers.

Consider a typical scenario: a mid-size SaaS team decides to move from AngularJS to React. They have a dozen internal libraries, a custom build pipeline, and a mix of unit and integration tests. Without an audit, they might not realize that their primary state management library has no React-compatible version, or that their build tool requires a plugin that only works with the old framework. The result is a stalled migration and a demoralized team.

Common failure modes include:

• Unplanned dependency rewrites that delay the project by months.
• Performance regressions that are only caught after deployment.
• Team skill gaps that surface only during the coding phase.
• Incomplete test coverage that leads to undetected bugs in production.

The audit doesn't eliminate risk, but it transforms unknown unknowns into known risks that can be managed. Teams that skip this step often end up with a hybrid codebase that is harder to maintain than either the old or new framework alone. Our goal is to help you avoid that outcome.

2. Prerequisites: What to Settle Before You Start the Audit

Before diving into the checklist, you need a shared understanding of the migration's scope and constraints. This context will shape every audit decision.

Define Your Migration Goals

Why are you switching? The answer must be specific. "Better performance" is too vague; "reduce initial load time from 4 seconds to under 2 seconds" is measurable. Other common goals include improved developer productivity, access to a richer ecosystem, or long-term maintainability. Write down the top three goals and rank them. This will help you make trade-offs later.

Set a Realistic Timeline

Most migrations take longer than expected. A good rule of thumb is to multiply your initial estimate by 1.5 to 2. Factor in learning time, unexpected dependency issues, and the inevitable scope creep. If the business cannot tolerate a 6-month migration window, you may need to consider a phased approach or even a different framework.

Assemble the Right Team

You need at least one person who deeply understands the current framework and one who is proficient in the target framework. If you don't have both, consider hiring a consultant or dedicating time for learning before the migration starts. A common mistake is to have the whole team learn the new framework simultaneously, which slows down both learning and delivery.

Secure Stakeholder Buy-In

Migrating a framework touches product, QA, DevOps, and often customer-facing teams. Make sure everyone understands that there will be a period of reduced feature velocity. A pre-migration audit is the perfect document to share with stakeholders to justify the timeline and resources.

3. The Core Workflow: 10 Points to Audit

This is the heart of the checklist. Each point represents a critical area that must be evaluated before you write a single line of new framework code.

Point 1: Map Your Dependency Tree

Create a complete graph of every package, plugin, and library your project depends on, including transitive dependencies. For each one, answer: Is there a compatible version for the target framework? If not, is there a drop-in replacement? How much effort would it be to replace it? Tools like npm ls, yarn why, or depcheck can help, but manual inspection of package.json and node_modules is still essential for catching edge cases.

Point 2: Audit Build and Configuration Files

Your build pipeline likely includes framework-specific plugins, loaders, and configurations. Webpack, Babel, ESLint, and TypeScript configs all need review. For example, a Vue project might use vue-loader and @vue/babel-preset-app; in a React migration, these must be replaced with babel-preset-react and appropriate loaders. Don't forget CI/CD scripts that may hardcode framework-specific commands.

Point 3: Review Your Component Architecture

Analyze how components are structured, how they communicate (props, events, stores), and how state is managed. Some patterns transfer well across frameworks (e.g., container/presenter), while others are tightly coupled to the old framework. Identify components that are heavily reliant on framework-specific features like Angular directives or Vue mixins. These will require the most rework.

Point 4: Assess Your Test Suite

Not all tests are created equal. Unit tests that mock framework internals may be worthless after a migration. Integration tests that test user flows are more resilient. Audit your test suite to identify which tests can be ported as-is, which need rewriting, and which can be deleted. Also check your testing framework: if you use a framework-specific testing utility (e.g., Vue Test Utils), you'll need to switch to a counterpart like React Testing Library.

Point 5: Evaluate Performance Baselines

Before you change anything, measure key performance metrics: initial load time, time to interactive, bundle size, and runtime rendering speed. Use tools like Lighthouse, WebPageTest, or browser DevTools. Without a baseline, you won't know if the migration actually improves performance or makes it worse. Store these numbers in a shared document that the team can refer to.

Point 6: Check Third-Party Integrations

Does your app integrate with an analytics SDK, a payment gateway, or a chat widget? These third-party scripts often expect a specific framework environment. Verify that the vendor supports the target framework or has a framework-agnostic version. If not, you may need to implement a custom integration layer, which adds risk.

Point 7: Review Routing and Navigation

Routing is often deeply tied to the framework. Angular's Router, Vue Router, and React Router have different APIs and capabilities. List all routes, guards, lazy-loaded modules, and navigation hooks. Plan how each will be migrated. Pay special attention to dynamic routing patterns, which can be tricky to replicate.

Point 8: Audit Server-Side Rendering (if applicable)

If your app uses SSR, the migration path is more complex. Each framework has its own SSR solution (Next.js for React, Nuxt for Vue, Angular Universal). You'll need to rebuild your server-side rendering logic from scratch. Also check your hosting environment: does it support Node.js for SSR, or do you need to adjust?

Point 9: Examine State Management

State management libraries are often framework-specific. If you use Redux, it works with any framework, but if you use Vuex or NgRx, you'll need to migrate to a new solution. Even if you use Redux, the way you connect components to the store changes. Audit your state shape, actions, and selectors to understand what can be reused.

Point 10: Evaluate Team Skills and Training Needs

Finally, be honest about your team's proficiency with the target framework. A team that has only used Angular will have a steep learning curve with React or Svelte. Plan for pair programming, workshops, or dedicated learning time. A common mistake is to assume that "JavaScript is JavaScript" and skip training, which leads to poorly written code and slow progress.

4. Tools, Setup, and Environment Realities

Having a checklist is one thing; executing it requires the right tools and environment. Here's what you need to set up.

Create a Sandbox Environment

Set up a separate branch or a fresh repository where you can prototype the migration without affecting the main codebase. This should mirror your production environment as closely as possible, including CI/CD pipelines, environment variables, and database connections. Use Docker or a similar containerization tool to ensure consistency across team members.

Use Scaffolding Tools

Most frameworks offer CLI tools to generate boilerplate (create-react-app, Vue CLI, Angular CLI). Use these to quickly set up a prototype of a few key pages. This will reveal integration issues early. Also consider using codemods—automated scripts that can transform old framework patterns into new ones. They are not perfect, but they can handle repetitive tasks like renaming lifecycle methods.

Set Up a Performance Budget

Define a performance budget for the new app. For example, the bundle size must not exceed 200 KB, or the time to interactive must be under 3 seconds. Use tools like bundlesize or webpack-bundle-analyzer to enforce these limits during development. This prevents the new codebase from accumulating bloat.

Establish a Rollback Plan

Before you deploy any migrated code, define clear rollback criteria. What metrics will tell you that the migration is not ready? Common criteria include a 10% increase in error rate, a 20% increase in load time, or a drop in user engagement. Also decide how you will roll back: by reverting a commit, switching a feature flag, or deploying the old version. Test the rollback process before the actual migration.

5. Variations for Different Constraints

Not every team has the luxury of a full migration. Here are common variations and how to adjust the checklist.

Incremental Migration (Strangler Fig Pattern)

If you cannot afford a big-bang rewrite, use the strangler fig pattern: gradually replace pieces of the old app with the new framework, routing traffic to the new code as it's ready. In this case, focus the audit on the interface between old and new. You'll need to establish a communication layer (e.g., iframes, micro-frontends, or a shared event bus). The checklist points about routing and state management become even more critical because both frameworks must coexist.

Small Team or Solo Developer

If you are a team of one or two, the audit is even more important because you have less capacity to recover from mistakes. Prioritize Points 1 (dependencies) and 10 (skills). Consider using a framework with a gentler learning curve, like Svelte or Preact, to reduce the skill gap. Also, be ruthless about scope: migrate only the most critical parts first, and defer non-essential features.

Legacy Codebase with No Tests

If your codebase has little or no test coverage, the audit must include a plan to add tests for the most critical user flows before migration. Otherwise, you will have no safety net. Start with end-to-end tests using a tool like Cypress or Playwright, which are framework-agnostic. Once you have those, you can begin migration with confidence.

Performance-Critical Application

For apps where every millisecond matters (e.g., real-time trading dashboards, video streaming interfaces), the performance baseline (Point 5) is non-negotiable. You may also need to run A/B tests in production to compare the old and new versions side by side. Consider using the new framework only for a subset of users initially to gather real-world performance data.

6. Pitfalls, Debugging, and What to Check When It Fails

Even with a thorough audit, things can go wrong. Here are common pitfalls and how to diagnose them.

Pitfall: Underestimating Dependency Complexity

You mapped your dependencies, but you missed a transitive dependency that only breaks at runtime. To avoid this, run a full build and test suite in the sandbox environment before starting the migration. Use a tool like npm audit or snyk to check for deprecated or unmaintained packages.

Pitfall: Performance Regression That Slips Through

Your baseline numbers looked good, but after migration, the app feels slower. This often happens because the new framework introduces additional overhead (e.g., virtual DOM diffing in React can be slower than Vue's direct DOM manipulation in certain cases). Profile the app using the browser's performance tab and compare against the baseline. If the regression is in a specific component, consider rewriting it using a more performant pattern or even keeping it in the old framework temporarily.

Pitfall: Team Morale Drops

Migration is mentally taxing. Developers may feel overwhelmed by the new framework, especially if they were experts in the old one. To mitigate this, schedule regular knowledge-sharing sessions and celebrate small wins (e.g., the first migrated page that passes all tests). Avoid blaming the old framework or the team for the difficulty; frame it as a learning opportunity.

What to Check When the Build Breaks

If the build fails after migration, start by checking the build configuration. Compare the old and new webpack.config.js or vite.config.ts side by side. Look for missing loaders, incorrect entry points, or incompatible plugins. Next, check the dependency versions: a minor version bump in a core library can cause breaking changes. Finally, review the error logs for stack traces that point to framework-specific code.

What to Check When Tests Fail

If unit tests fail, they are likely mocking framework internals that no longer exist. Rewrite those tests to test behavior rather than implementation. For integration tests, check that the testing environment is configured correctly (e.g., JSDOM vs. real browser). If end-to-end tests fail, the selectors or page structure may have changed due to different rendering behavior.

When to Abandon and Restart

If after two weeks of migration you have made no measurable progress, it may be time to reconsider the approach. Common reasons include choosing the wrong framework, insufficient team skills, or a codebase that is too tightly coupled. In these cases, it's better to pause, reassess, and possibly start over with a different strategy (e.g., incremental migration) than to push forward and waste months. The pre-migration audit is not a one-time event; revisit it if the situation changes.

Next Steps: From Audit to Action

Once you have completed the audit, you should have a clear picture of what the migration will entail. Your next moves are:

1. Prioritize the findings: Rank the audit points by risk level. Address high-risk items first (e.g., missing dependency replacement, lack of test coverage).
2. Create a phased migration plan: Break the migration into small, deliverable chunks. Each chunk should be independently testable and deployable.
3. Set up a communication cadence: Share progress with stakeholders weekly. Use the audit document as a reference to explain delays or scope changes.
4. Build a prototype of the riskiest component: Before committing to the full migration, build a small proof-of-concept that exercises the most complex part of your app. This will validate your assumptions.
5. Define success criteria: Agree on what "done" looks like. It could be the percentage of pages migrated, performance metrics met, or all tests passing. Celebrate when you hit those milestones.

Migration is a journey, not a single event. A thorough pre-migration audit is your map. Use it, update it as you learn, and don't skip the steps. Your future self—and your users—will thank you.