Experience case study • Platform migration
Migrating a legacy framework containing thousands of tests to a distributed CI/CD platform
I led a six-month migration while product development and release validation continued on the legacy framework.
Overview
I led the migration of a legacy automation framework containing thousands of test cases to a modern CI/CD-integrated platform.
The validation suite for one of our optical-networking products ran on remote Linux servers without centralized execution, logs, history, or standardized workflows. The migration proceeded while development and release validation continued on the legacy framework.
For approximately six months, both frameworks evolved in parallel. The main challenge was keeping them synchronized until the new platform could safely and completely replace the legacy system.
Approach
I led a two-person migration effort.
- I migrated the entire shared-library layer.
- I owned integration with the distributed platform and CI/CD workflows.
- The other engineer focused primarily on migrating individual test scripts.
- Together, we migrated thousands of test cases across the sanity, smoke, and regression suites.
- I built a dashboard to track progress, ownership, and synchronization.
- I ensured ongoing legacy changes were reflected in migrated components.
- I delivered code walkthroughs and training to support the team’s transition.
Migration architecture
- Legacy pathDevelopment and release validation continue
- Migration controlOwnership, dependencies, and changes stay synchronized
- New platformDistributed execution and CI/CD become the destination
Controlled replacement path
Progress is necessary; equivalent behaviour is the cutover gate.
- OperateKeep liveLegacy validation continues
- ControlSynchronizeTrack changes and ownership
- MigrateMove foundationsLibraries before scripts
- VerifyCompareScenarios, results, and time
- CutoverReplaceRetire the legacy path
Cutover guardrailLegacy-framework engineers verify required scenarios before retirement; confidential implementation details remain excluded.
Cutover validation
Before retiring the legacy framework:
- Equivalent scenarios were executed through both frameworks.
- Test results were compared to identify behavioural differences and migration defects.
- Sanity and full-regression execution times were compared.
- Legacy-framework engineers verified that the required scenarios were preserved in the migrated suites.
Outcome
The migration was completed in approximately six months without interrupting release validation.
- The legacy framework was retired.
- Validation moved to the distributed platform.
- Execution, logs, history, and CI/CD workflows became centralized.
- Engineers no longer needed to manage execution infrastructure manually.
What other engineers can reuse
Treat synchronization as migration work
When old and new systems evolve together, every relevant legacy change needs an explicit reconciliation path.
Migrate shared dependencies first
Moving common libraries before individual tests reduces duplicated effort and downstream rework.
Measure equivalence, not progress
A migrated test count does not prove readiness. Compare scenarios, results, coverage, and execution time.
Include legacy experts
Engineers who understand the original system can identify behavioural gaps that automated comparisons may miss.
Plan knowledge transfer
A replacement is not operationally complete until its future maintainers can understand and support it.
Key takeaway
A migration is complete only when the new system reproduces the required behaviour, the two implementations have stopped drifting, and the receiving team can operate the replacement independently.
Public evidence boundary: This case study excludes confidential architecture, product details, internal measurements, staffing information, and customer information.
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