A platform migration is testable when the team records current critical behavior, runs the same paths on the target, and explains every accepted difference before production traffic moves.
Record the behavior that must survive
Framework and platform tests often concentrate on routes and components, while production failures appear in identity callbacks, cookies, caching, file handling, background work, time zones, redirects, headers, and provider-specific limits. The migration inventory turns those dependencies into representative user and operator paths before implementation begins.
Each path starts with a known state, performs observable actions, and ends with a result that can be checked in the interface, datastore, queue, logs, or external system. Current production supplies the baseline when its behavior is intentional. Known defects remain labeled so the migration does not silently canonize them.
Layer deterministic checks under smoke tests
The target should pass its build, type, schema, lint, unit, and integration checks before a person evaluates full paths. Those deterministic failures are cheaper to diagnose and should block a cutover rehearsal. A clean build alone remains insufficient because it proves that the target compiled, not that an account can sign in and complete the product's promised work.
Critical-path smoke tests then exercise identity, reads, writes, jobs, webhooks, emails, payments, file operations, and other in-scope integrations. Each result records the target environment, configuration version, test account, timestamp, and evidence location so another developer can reproduce the finding.
Test rollback with the same seriousness
A rollback script that has never run is only a proposal. The rehearsal should move a safe environment to the target, create representative state, trigger a failure condition, reverse traffic or deployment, and verify what data and queued work survived. The final report separates reversible code and configuration changes from data transformations that need a forward repair.
Where the service stops
Reality Contact, LLC prepares and validates the migration, but does not choose the buyer's target platform, receive secrets through the public form, approve downtime, change DNS, move production data, or initiate the final cutover without the buyer's authorization. The buyer supplies target decisions and scoped access, places production secrets, approves the verified release window, and executes or authorizes the final production cutover and any rollback. The work is software implementation and operational documentation, and it does not replace security, legal, compliance, or business-continuity advice. The buyer retains production credentials, approves downtime and data handling, and authorizes every cutover, traffic, DNS, and rollback action.
Sources: AWS guidance on migration testing; Google Cloud migration services.